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ltc4090/ltc4090-5 1 4090fc features applications description usb power manager with 2a high voltage bat-track buck regulator the ltc ? 4090/ltc4090-5 are usb power managers plus high voltage li-ion/polymer battery chargers. the devices control the total current used by the usb peripheral for operation and battery charging. battery charge current is automatically reduced such that the sum of the load current and the charge current does not exceed the programmed input current limit. the ltc4090/ltc4090-5 also accom- modate high voltage power supplies, such as 12v ac/dc wall adapters, firewire, or automotive power. the ltc4090 provides a bat-track adaptive output that tracks the battery voltage for high ef? ciency charging from the high voltage input. the ltc4090-5 provides a ? xed 5v output from the high voltage input to charge single-cell li-ion batteries. the charge current is programmable and an end-of-charge status output ( chrg ) indicates full charge. also featured are programmable total charge time, an ntc thermistor input used to monitor battery temperature while charging and automatic recharging of the battery. n seamless transition between power sources: li-ion battery, usb, and 6v to 36v supply (60v max) n 2a output high voltage buck regulator with bat-track? adaptive output control (ltc4090) n internal 215m ideal diode plus optional external ideal diode controller provides low loss power path when external supply / usb not present n load dependent charging from usb input guarantees current compliance n full featured li-ion battery charger n 1.5a maximum charge current with thermal limiting n ntc thermistor input for temperature quali? ed charging n tiny (3mm 6mm 0.75mm) 22-pin dfn package n hdd-based media players n personal navigation devices n other usb-based handheld products n automotive accessories hvin boost in sw 4.7f 22f 4.7f 1f timer clprog ltc4090 gnd prog hvout hvpr out bat 0.1f 270pf 100k 2k 5v wall adapter usb high (7.5v-36v) voltage input v c 59k r t 40.2k li-ion battery + 1k load 4090 tao1 v out (typ) v bat + 0.3v 5v 5v v bat available input hv input (ltc4090) hv input (ltc4090-5) usb only bat only 6.8h 0.47f ltc4090/ltc4090-5 high voltage battery charger ef? ciency v bat (v) 2.0 efficiency (%) 70 80 90 4.0 4090 ta01b 60 50 20 40 30 2.5 3.0 3.5 4.5 figure 12 schematic with r prog = 52k no output load hvin = 8v hvin = 12v hvin = 24v hvin = 36v ltc4090 ltc4090-5 typical application l , lt, ltc and ltm are registered trademarks of linear technology corporation. bat-track is a trademark of linear technology corporation. all other trademarks are the property of their respective owners.
ltc4090/ltc4090-5 2 4090fc pin configuration absolute maximum ratings hvin, hven (note 9) ................................................60v boost ......................................................................56v boost above sw .....................................................30v pg, sync ..................................................................30v in, out, hvout t < 1ms and duty cycle < 1% .................. C0.3v to 7v steady state ............................................. C0.3v to 6v bat, hpwr, susp, v c , chrg , hvpr ........... C0.3v to 6v ntc, timer, prog, clprog ..........C0.3v to v cc + 0.3v i in , i out , i bat (note 5) ..............................................2.5a operating temperature range......................C40 to 85c junction temperature ........................................... 110c storage temperature range .......................C65 to 125c (notes 1, 2, 3, 4) 22 21 20 19 18 17 16 15 14 13 12 1 2 3 4 5 6 7 8 9 10 11 hven hvin sw boost hvout timer susp hpwr clprog out in top view 23 djc package 22-lead ( 6mm s 3mm ) plastic dfn sync pg r t v c ntc vntc hvpr chrg prog gate bat t jmax = 110c, ja = 47c/w exposed pad (pin 23) is gnd, must be soldered to pcb symbol parameter conditions min typ max units usb input current limit v in usb input supply voltage l 4.35 5.5 v i in input bias current i bat = 0 (note 6) suspend mode; susp = 5v l l 0.5 50 1 100 ma a i lim current limit hpwr = 5v hpwr = 0v l l 475 90 500 100 525 110 ma ma i in(max) maximum input current limit (note 7) 2.4 a r on on-resistance v in to v out i out = 80ma 0.215 v clprog clprog servo voltage in current limit r clprog = 2k r clprog = 1k l l 0.98 0.98 1.00 1.00 1.02 1.02 v v i ss soft-start inrush current 10 ma/s the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. hvin = hven = 12v, boost = 17v, v in = hpwr = 5v, v bat = 3.7v, r prog = 100k, r clprog = 2k and susp = 0v, unless otherwise noted. lead free finish tape and reel part marking package description temperature range ltc4090edjc#pbf ltc4090edjc#trpbf 4090 22-lead (6mm 3mm) plastic dfn C40c to 85c ltc4090edjc-5#pbf ltc4090edjc-5#trpbf 40905 22-lead (6mm 3mm) plastic dfn C40c to 85c consult ltc marketing for parts speci? ed with wider operating temperature ranges. consult ltc marketing for information on non-standard lead based ? nish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel speci? cations, go to: http://www.linear.com/tapeandreel/ order information electrical characteristics
ltc4090/ltc4090-5 3 4090fc electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. hvin = hven = 12v, boost = 17v, v in = hpwr = 5v, v bat = 3.7v, r prog = 100k, r clprog = 2k and susp = 0v, unless otherwise noted. symbol parameter conditions min typ max units v clen input current limit enable threshold voltage (v in - v out ) (v in - v out ) rising (v in - v out ) falling 20 C80 50 C50 80 C20 mv mv v uvlo input undervoltage lockout v in rising l 3.6 3.8 4 v v uvlo input undervoltage lockout hysteresis v in rising C v in falling 130 mv high voltage regulator v hvin hvin supply voltage l 660v v ovlo hvin overvoltage lockout threshold l 36 38 40 v i hvin hvin bias current shutdown; hven = 0.2v not switching, hvout = 3.6v l 0.01 130 0.5 200 a a v out output voltage with hvin present assumes hvout to out connection, 0 v bat 4.2v (ltc4090) 3.45 v bat + 0.3 4.6 v v out output voltage with hvin present assumes hvout to out connection (ltc4090-5) 4.85 5 5.15 v f sw switching frequency r t = 8.66k r t = 29.4k r t = 187k 2.1 0.9 160 2.4 1.0 200 2.7 1.15 240 mhz mhz khz t off minimum switch off-time l 60 150 ns i sw(max) switch current limit duty cycle = 5% 3.0 3.5 4.0 a v sat switch v cesat i sw = 2a 500 mv i r boost schottky reverse leakage sw = 10v, hvout = 0v 0.02 2 a v b(min) minimum boost voltage (note 8) l 1.5 2.1 v i bst boost pin current i sw = 1a 22 35 ma battery management i bat battery drain current v bat = 4.3v, charging stopped suspend mode, susp = 5v v in = 0v, bat powers out, no load l l l 15 22 60 27 35 100 a a a v float v bat regulated output voltage i bat = 2ma i bat = 2ma; 0 t a 85c 4.165 4.158 4.200 4.200 4.235 4.242 v v i chg constant-current mode charge current, no load r prog = 100k r prog = 50k, 0 t a 85c l 465 900 500 1000 535 1080 ma ma i chg(max) maximum charge current 1.5 a v prog prog pin servo voltage r prog = 100k r prog = 50k l l 0.98 0.98 1.00 1.00 1.02 1.02 v v k eoc ratio of end-of-charge indication current to charge current v bat = v float (4.2v) l 0.085 0.1 0.11 ma/ma i trkl trickle charge current bat = 2v 35 50 60 ma v trkl trickle charge threshold voltage bat rising l 2.75 2.9 3.0 v v cen charge enable threshold voltage (v out C v bat ) falling; v bat = 4v (v out C v bat ) rising; v bat = 4v 55 80 mv mv v rechrg recharge battery threshold voltage threshold voltage relative to v float l C65 C100 C135 mv
ltc4090/ltc4090-5 4 4090fc symbol parameter conditions min typ max units t timer timer accuracy v bat = 4.3v C10 10 % recharge time percent of total charge time 50 % low battery trickle charge time percent of total charge time, v bat <2.9v 25 % t lim junction temperature in constant- temperature mode 105 c internal ideal diode r fwd incremental resistance, v on regulation i out = 100ma 125 m r dio, on on-resistance v bat to v out i out = 600ma 215 m v fwd voltage forward drop (v bat C v out )i out = 5ma i out = 100ma i out = 600ma l 10 30 55 160 50 mv mv mv v off diode disable battery voltage 2.7 v i fwd load current limit for v on regulation 550 ma i d(max) diode current limit 2.2 a external ideal diode v fwd, ext external diode forward voltage 20 mv logic ( chrg , hvpr , timer, susp , hpwr, hven, pg, sync) v chg, sd charger shutdown threshold voltage on timer l 0.14 0.4 v i chg, sd charger shutdown pull-up current on timer v timer = 0v l 514 a v ol output low voltage ( chrg , hvpr ); i sink = 5ma l 0.1 0.4 v v ih input high voltage susp , hpwr 1.2 v v il input low voltage susp , hpwr 0.4 v v hven, h hven high threshold 2.3 v v hven, l hven low threshold 0.3 v i pulldn logic input pull-down current susp , hpwr 2 a i hven hven pin bias current hven = 2.5v 5 10 a v pg pg threshold hvout rising 2.8 v v pg pg hysteresis 35 mv i pglk pg leakage pg = 5v 0.1 1 a i pg pg sink current pg = 0.4v l 100 900 a v sync, l sync low threshold 0.5 v v sync, h sync high threshold 0.8 v i sync sync pin bias current v sync = 0v 0.1 a electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. hvin = hven = 12v, boost = 17v, v in = hpwr = 5v, v bat = 3.7v, r prog = 100k, r clprog = 2k and susp = 0v, unless otherwise noted.
ltc4090/ltc4090-5 5 4090fc i bat (ma) 0 4.00 v float (v) 4.05 4.10 4.15 4.20 4.25 4.30 200 400 600 800 4090 g01 1000 r prog = 34k temperature (c) C50 v float (v) 4.195 4.200 4.205 25 75 4090 g02 4.190 4.185 4.180 C25 0 50 4.210 4.215 4.220 100 v in = 5v i bat = 2ma time (min) 0 v bat , v out , v chrgb (v) i bat (ma) 2 3 200 4090 g03 1 0 50 100 150 5 4 600 900 300 0 1500 1200 v bat v out v chrgb i bat 1250mah cell hvin = 12v r prog = 50k c/10 termination note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: the ltc4090/ltc4090-5 are guaranteed to meet performance speci? cations from 0c to 85c. speci? cations over the C40c to 85c operating temperature range are assured by design, characterization and correlation with statistical process controls. note 3: this ic includes overtemperature protection that is intended to protect the device during momentary overload conditions. junction temperatures will exceed 110c when overtemperature protection is active. continuous operation above the speci? ed maximum operating junction temperature may result in device degradation or failure. note 4: v cc is the greater of v in , v out , and v bat note 5: guaranteed by long term current density limitations. note 6: total input current is equal to this speci? cation plus 1.002 ? i bat where i bat is the charge current. note 7: accuracy of programmed current may degrade for currents greater than 1.5a. note 8: this is the minimum voltage across the boost capacitor needed to guarantee full saturation of the switch. note 9: absolute maximum voltage at hvin and hven pins is for nonrepetative 1 second transients; 40v for continuous operation. electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. hvin = hven = 12v, boost = 17v, v in = hpwr = 5v, v bat = 3.7v, r prog = 100k, r clprog = 2k and susp = 0v, unless otherwise noted. symbol parameter conditions min typ max units ntc i vntc vntc pin current vntc = 2.5v l 1.4 2.5 3.5 ma v vntc vntc bias voltage i vntc = 500a l 4.4 4.85 v i ntc ntc input leakage current ntc = 1v 0 1 a v cold cold temperature fault threshold voltage rising ntc voltage hysteresis 0.738 ? vntc 0.02 ? vntc v v v hot hot temperature fault threshold voltage falling ntc voltage hysteresis 0.29 ? vntc 0.01 ? vntc v v v dis ntc disable threshold voltage falling ntc voltage hysteresis l 75 100 35 125 mv mv v float load regulation battery regulation (float) voltage vs temperature battery current and voltage vs time (ltc4090) typical performance characteristics
ltc4090/ltc4090-5 6 4090fc switch current (ma) 0 400 500 700 1500 4090 g12 300 200 500 1000 2000 2500 100 0 600 voltage drop (mv) 0 3000 4000 5000 80 4090 g07 2000 1000 2500 3500 4500 1500 500 0 20 40 60 100 v fwd (mv) i out (ma) v bat = 3.7v v in = 0v si2333 pfet C50c 0c 50c 100c v bat (v) 0 0 i bat (ma) 100 300 400 500 1 2 2.5 4.5 4090 g04 200 0.5 1.5 3 3.5 4 600 v in = 5v v out = no load r prog = 100k r clprog = 2k hpwr = 5v hpwr = 0v temperature (c) C50 i bat (ma) 400 500 600 25 75 4090 g05 300 200 C25 0 50 100 125 100 0 r prog = 2.1k v in = 5v v bat = 3.5v q ja = 40c/w v fwd (mv) 0 0 i out (ma) 100 300 400 500 1000 700 50 100 4090 g06 200 800 900 600 150 200 v bat = 3.7v v in = 0v C50c 0c 50c 100c i out (a) 0 efficiency (%) 80 90 100 0.8 4090 g08 70 60 75 85 95 65 55 50 0.2 0.4 0.6 1.0 hvin = 8v hvin = 12v hvin = 24v hvin = 36v figure 12 schematic v bat = 4.21v (i bat = 0) hvin (v) 5 1.8 i out (a) 2.0 2.2 2.4 2.6 3.0 10 15 20 25 4090 g10 30 35 2.8 figure 12 schematic v bat = 4.21v (i bat = 0) typical minimum temperature (?c) minimum switch on time (ns) 80 100 120 4090 g11 60 40 20 0 140 C50 25 C25 0 50 75 100 15 0 125 typical performance characteristics charging from usb, i bat vs v bat charge current vs temperature (thermal regulation) ideal diode current vs forward voltage and temperature (no external device) ideal diode current vs forward voltage and temperature with external device ltc4090 high voltage regulator ef? ciency vs output load high voltage regulator maximum load current high voltage regulator minimum switch on-time vs temperature high voltage regulator switch voltage drop i out (a) 0 efficiency (%) 80 90 100 0.8 4090 g09 70 60 75 85 95 65 55 50 0.2 0.4 0.6 1.0 hvin = 8v hvin = 12v hvin = 24v hvin = 36v figure 12 schematic v bat = 4.21v (i bat = 0) ltc4090-5 high voltage regulator ef? ciency vs output load
ltc4090/ltc4090-5 7 4090fc temperature (c) C50 hvout threshold voltage (v) 2.80 2.85 2.90 25 75 150 4090 g21 2.75 2.70 2.65 C25 0 50 100 125 duty cycle (%) 0 switch current limit(a) 40 4090 g16 2.5 20 60 1.5 1.0 4.0 3.5 3.0 2.0 80 100 hven pin voltage (v) 0 switch current limit (a) 3.5 1.5 4090 g15 2.0 1.0 0.5 1 2 0.5 0 4.0 3.0 2.5 1.5 2.5 3 3.5 temperature (c) C50 500 frequency (khz) 600 700 800 900 050 100 150 4090 g13 1000 1100 C25 25 75 125 hvout (v) 0 0 switching frequency (khz) 100 300 400 500 1000 700 1 2 4090 g14 200 800 900 600 3 4 boost diode current (a) 0 boost diode v f (v) 0.8 1.0 1.2 2.0 4090 g19 0.6 0.4 0 0.5 1.0 1.5 0.2 1.4 load current (ma) 1 5.0 hvin (v) 6.0 7.0 10 100 1000 4090 g18 4.0 4.5 5.5 6.5 3.5 3.0 to start to run temperature (c) v c voltage (v) 1.50 2.00 2.50 4090 g20 1.00 0.50 0 current limit clamp switching threshold C50 25 C25 0 50 75 100 150 125 typical performance characteristics high voltage regulator switch frequency high voltage regulator frequency foldback high voltage regulator soft-start high voltage regulator switch current limit high voltage regulator minimum input voltage high voltage regulator boost diode v f vs i f high voltage regulator v c voltages high voltage regulator power good threshold temperature (c) switch current limit (a) 2.0 2.5 3.5 3.0 4090 g17 1.5 1.0 0 0.5 4.5 4.0 duty cycle = 10 % duty cycle = 90 % C50 25 C25 0 50 75 100 150 125 high voltage regulator switch current limit
ltc4090/ltc4090-5 8 4090fc 100s/div hpwr 5v/div i in 0.5a/div i bat 0.5a/div 4090 g27 v bat = 3.85v i out = 50ma typical performance characteristics ltc4090 input connect waveforms ltc4090 input disconnect waveforms ltc4090 response to suspend ltc4090 high voltage input connect waveforms ltc4090 high voltage input disconnect waveforms ltc4090 high voltage regulator load transient ltc4090 high voltage regulator load transient 1ms/div v in 5v/div v out 5v/div i in 0.5a/div i bat 0.5a/div 4090 g22 v bat = 3.85v i out = 100ma 1ms/div v in 5v/div v out 5v/div i in 0.5a/div i bat 0.5a/div 4090 g23 v bat = 3.85v i out = 100ma 1ms/div susp 5v/div v out 5v/div i in 0.5a/div i bat 0.5a/div 4090 g24 v bat = 3.85v i out = 50ma 2ms/div v hvin 10v/div v out 5v/div i hvin 1a/div i bat 1a/div 4090 g25 v bat = 3.85v i out = 100ma 2ms/div v hvin 5v/div v out 5v/div i hvin 1a/div i bat 1a/div 4090 g26 v bat = 3.85v i out = 100ma ltc4090 response to hpwr 25s/div hvout 50mv/div i out 1a/div 4090 g28 i load = 500ma 25s/div hvout 50mv/div i l 1a/div 4090 g29 i load = 500ma
ltc4090/ltc4090-5 9 4090fc pin functions sync (pin 1): external clock synchronization input. see synchronizing section in the applications information section. ground pin when not used. pg (pin 2): open collector output of an internal compara- tor. pg remains low until the hvout pin is above 2.8v. pg output is valid when hvin is above 3.6v and hven is high. r t (pin 3): oscillator resistor input. connecting a resistor to ground from this pin sets the switching frequency. v c (pin 4): high voltage buck regulator control pin. the voltage on this pin controls the peak switch current in the high voltage regulator. tie an rc network from this pin to ground to compensate the control loop. ntc (pin 5): input to the ntc thermistor monitoring circuits. the ntc pin connects to a negative temperature coef? cient thermistor which is typically co-packaged with the battery pack to determine if the battery is too hot or too cold to charge. if the battery temperature is out of range, charging is paused until the battery temperature re-enters the valid range. a low drift bias resistor is required from vntc to ntc and a thermistor is required from ntc to ground. if the ntc function is not desired, the ntc pin should be grounded. vntc (pin 6): output bias voltage for ntc. a resistor from this pin to the ntc pin will bias the ntc thermistor. hvpr (pin 7): high voltage present output (active low). a low on this pin indicates that the high voltage regulator has suf? cient voltage to charge the battery. this feature is enabled if power is present on hvin, in, or bat (i.e., above uvlo thresholds). chrg (pin 8): open-drain charge status output. when the battery is being charged, the chrg pin is pulled low by an internal n-channel mosfet. when the timer runs out or the charge current drops below 10% of the programmed charge current or the input supply is removed, the chrg pin is forced to a high impedance state. prog (pin 9): charge current program pin. connecting a resistor from prog to ground programs the charge current: i chg (a) = 50,000v r prog gate (pin 10): external ideal diode gate connection. this pin controls the gate of an optional external p-channel mosfet transistor used to supplement the internal ideal diode. the source of the p-channel mosfet should be connected to out and the drain should be connected to bat. when not in use, this pin should be left ? oating. it is important to maintain high impedance on this pin and minimize all leakage paths. bat (pin 11): single-cell li-ion battery. this pin is used as an output when charging the battery and as an input when supplying power to out. when the out pin potential drops below the bat pin potential, an ideal diode function connects bat to out and prevents out from dropping more than 100mv below bat. a precision internal resistor divider sets the ? nal ? oat (charging) potential on this pin. the internal resistor divider is disconnected when in and hvin are in undervoltage lockout. in (pin 12): input supply. connect to usb supply, v bus . input current to this pin is limited to either 20% or 100% of the current programmed by the clprog pin as deter- mined by the state of the hpwr pin. charge current (to the bat pin) supplied through the input is set to the current programmed by the prog pin but will be limited by the input current limit if charge current is set greater than the input current limit or if the sum of charge current plus load current is greater than the input current limit. out (pin 13): voltage output. this pin is used to provide controlled power to a usb device from either usb v bus (in), an external high voltage supply (hvin), or the battery (bat) when no other supply is present. the high voltage supply is prioritized over the usb v bus input. out should be bypassed with at least 4.7f to gnd.
ltc4090/ltc4090-5 10 4090fc clprog (pin 14): current limit program and input cur- rent monitor. connecting a resistor, r clprog , to ground programs the input to output current limit. the current limit is programmed as follows: i cl (a) = 1000v r clprog in usb applications, the resistor r clprog should be set to no less than 2.1k. the voltage on the clprog pin is always proportional to the current ? owing through the in to out power path. this current can be calculated as follows: i in (a) = v clprog r clprog ? 1000 hpwr (pin 15): high power select. this logic input is used to control the input current limit. a voltage greater than 1.2v on the pin will set the input current limit to 100% of the current programmed by the clprog pin. a voltage less than 0.4v on the pin will set the input current limit to 20% of the current programmed by the clprog pin. a 2a pull-down current is internally connected to this pin to ensure it is low at power up when the pin is not being driven externally. susp (pin 16): suspend mode input. pulling this pin above 1.2v will disable the power path from in to out. the supply current from in will be reduced to comply with the usb speci? cation for suspend mode. both the ability to charge the battery from hvin and the ideal diode function (from bat to out) will remain active. suspend mode will reset the charge timer if out is less than bat while in suspend mode. if out is kept greater than bat, such as when the high voltage input is present, the charge timer will not be reset when the part is put in suspend. a 2a pull-down current is internally connected to this pin to ensure it is low at power up when the pin is not being driven externally. timer (pin 17): timer capacitor. placing a capacitor, c timer , to gnd sets the timer period. the timer period is: t timer (hours) = c timer ?r prog ? 3hours 0.1f ? 100k charge time is increased if charge current is reduced due to load current, thermal regulation and current limit selection (hpwr low). shorting the timer pin to gnd disables the battery charging functions. hvout (pin 18): voltage output of the high voltage regulator. when suf? cient voltage is present at hvout, the low voltage power path from in to out will be discon- nected and the hvpr pin will be pulled low to indicate that a high voltage wall adapter has been detected. the ltc4090 high voltage regulator will maintain just enough differential voltage between hvout and bat to keep the battery charger mosfet out of dropout (typically 300mv from out to bat). the ltc4090-5 high voltage regulator will provide a 5v output to the battery charger mosfet. hvout should be bypassed with at least 22f to gnd. boost (pin 19): this pin is used to provide drive voltage, higher than the input voltage, to the internal bipolar npn power switch. sw (pin 20): the sw pin is the output of the internal high voltage power switch. connect this pin to the inductor, catch diode and boost capacitor. hvin (pin 21): high voltage regulator input. the hvin pin supplies current to the internal high voltage regulation and to the internal high voltage power switch. the presence of a high voltage input takes priority over the usb v bus input (i.e., when a high voltage input supply is detected, the usb in to out path is disconnected). this pin must be locally bypassed. hven (pin 22): high voltage regulator enable input. the hven pin is used to disable the high voltage input path. tie to ground to disable the high voltage input or tie to at least 2.3v to enable the high voltage path. if this feature is not used, tie hven to the hvin pin. this pin can also be used to soft-start the high voltage regulator; see the applications information section for more information. exposed pad (pin 23): ground. the exposed package pad is ground and must be soldered to the pc board for proper functionality and for maximum heat transfer (use several vias directly under the ltc4090/ltc4090-5). pin functions
ltc4090/ltc4090-5 11 4090fc block diagram C + soft-start 0.25v soft-start2 C + C + C + C + 15 too cold current limit too hot 0.1v ntc enable v ntc 14 ntc t 10k r prog 10k C + 13 hpwr 22 clprog in 23 prog chg 1v 500ma/100ma 2 m a C + C + current control vc clamp charge control control logic voltage detect counter oscillator ta die temp 105c i lim 2.8v C + 2.9v battery uvlo 4.1v recharge uvlo in out bat i chg bat uv rechrg hold reset ntcerr clk eoc c/10 C + C + 11 2 a 16 gnd susp r clprog v set 3.6v (ltc4090) 5v (ltc4090-5) in hvout out out gate bat bat 21 timer c timer 18 chrg stop hvpr 4090 bd 1v cl i lim cntl enable C + eda 19 d1 c2 l1 i in 1000 10 c c r c c f pg hvin v c 10 cc/cv regulator charger enable C + C + 4.25v (rising) 3.15v (falling) C + 21 21 21 r s q r t1 10 c1 10 sync 10 r t 10 hven 10 C + + 75mv (rising) 25mv (falling) 350mv (ltc4090) gm boost q1 sw 20mv 30mv ideal diode q driver + C + C + C + C oscillator 200khz - 2.4mhz soft-start internal reference i l
ltc4090/ltc4090-5 12 4090fc operation introduction the ltc4090/ltc4090-5 are complete powerpath? controllers for battery powered usb applications. the ltc4090/ltc4090-5 are designed to receive power from a low voltage source (e.g., usb or 5v wall adapter), a high voltage source (e.g., firewire/ieee1394, automotive battery, 12v wall adapter, etc.), and a single-cell li-ion battery. they can then deliver power to an application connected to the out pin and a battery connected to the bat pin (assuming that an external supply other than the battery is present). power supplies that have limited current resources (such as usb v bus supplies) should be connected to the in pin which has a programmable current limit. battery charge current will be adjusted to ensure that the sum of the charge current and load cur- rent does not exceed the programmed input current limit (see figure 1). an ideal diode function provides power from the battery when output / load current exceeds the input current limit or when input power is removed. powering the load through the ideal diode instead of connecting the load directly to the battery allows a fully charged battery to remain fully charged until external power is removed. once external power is removed the output drops until the ideal diode is forward biased. the forward biased ideal diode will then provide the output power to the load from the battery. the ltc4090/ltc4090-5 also include a high voltage switching regulator which has the ability to receive power from a high voltage input. this input takes priority over the usb v bus input (i.e., if both hvin and in are present, load current and charge current will be delivered via the high voltage path). when enabled, the high voltage regulator regulates the hvout voltage using a constant frequency, current mode regulator. an external pfet between hvout (drain) and out (source) is turned on via the hvpr pin allowing out to charge the battery and/or supply power to the application. the ltc4090s bat-track maintains ap- proximately 300mv between the out pin and the bat pin, while the ltc4090-5 provides a ? xed 5v output. hvout out gate bat bat out hvpr 4090 f01 C + eda 19 d1 l1 cc/cv regulator charger high voltage buck regulator usb current limit enable C + C + 21 21 21 c1 hvin in q1 sw 30mv 30mv ideal diode 4.25v (rising) 3.15v (falling) 75mv (rising) 25mv (falling) + load li-ion + C + C + C figure 1. simpli? ed powerpath block diagram powerpath is a trademark of linear technology corporation
ltc4090/ltc4090-5 13 4090fc operation usb input current limit the input current limit and charge control circuits of the ltc4090/ltc4090-5 are designed to limit input current as well as control battery charge current as a function of i out . out drives the external load and the battery charger. if the combined load at out does not exceed the pro- grammed input current limit, out will be connected to in through an internal 215m p-channel mosfet. if the combined load at out exceeds the programmed input current limit, the battery charger will reduce its charge cur- rent by the amount necessary to enable the external load to be satis? ed while maintaining the programmed input current. even if the battery charge current is set to exceed the allowable usb current, a correctly programmed input current limit will ensure that the usb speci? cation is never violated. furthermore, load current at out will always be prioritized and only excess available current will be used to charge the battery. the input current limit, i cl , can be programmed using the following formula: i cl = 1000 r clprog ?v clprog ? ? ? ? ? ? = 1000v r clprog where v clprog is the clprog pin voltage (typically 1v) and r clprog is the total resistance from the clprog pin to ground. for best stability over temperature and time, 1% metal ? lm resistors are recommended. the programmed battery charge current, i chg , is de- ? ned as: i chg = 50,000 r prog ?v prog ? ? ? ? ? ? = 50,000v r prog input current, i in , is equal to the sum of the bat pin output current and the out pin output current. v clprog will track the input current according to the following equation: i in = i out + i bat = v clprog r clprog ? 1000 in usb applications, the maximum value for r clprog should be 2.1k. this will prevent the input current from exceeding 500ma due to ltc4090/ltc4090-5 tolerances and quiescent currents. a 2.1k clprog resistor will give a typical current limit of 476ma in high power mode (when hpwr is high) or 95ma in low power mode (when hpwr is low). when susp is driven to a logic high, the input power path is disabled and the ideal diode from bat to out will supply power to the application. high voltage step down regulator the power delivered from hvin to hvout is controlled by a constant-frequency, current mode step down regulator. an external p-channel mosfet directs this power to out and prevents reverse conduction from out to hvout (and ultimately hvin). an oscillator, with frequency set by r t , enables an rs ? ip- ? op, turning on the internal power switch. an ampli? er and comparator monitor the current ? owing between hvin and sw pins, turning the switch off when this current reaches a level determined by the voltage at v c . an error ampli? er servos the v c node to maintain approximately 300mv between out and bat (ltc4090). by keeping the voltage across the battery charger low, ef? ciency is optimized be- cause power lost to the battery charger is minimized and power available to the external load is maximized. if the bat pin voltage is less than approximately 3.3v, then the error ampli? er will servo the v c node to provide a constant hvout output voltage of about 3.6v (ltc4090). an active clamp on the v c node provides current limit. the v c node is also clamped to the voltage on the hven pin; soft-start is implemented by generating a voltage ramp at the hven pin using an external resistor and capacitor. the switch driver operates from either the high voltage input or from the boost pin. an external capacitor and internal diode are used to generate a voltage at the boost pin that is higher than the input supply. this allows the driver to fully saturate the internal bipolar npn power switch for ef? cient operation. to further optimize ef? ciency, the high voltage buck regu- lator automatically switches to burst mode ? operation in light load situations. between bursts, all circuitry associated with controlling the output switch is shut down reducing the input supply current. burst mode is a registered trademark of linear technology corporation
ltc4090/ltc4090-5 14 4090fc operation the oscillator reduces the switch regulators operating frequency when the voltage at the hvout pin is low (be- low 2.95v). this frequency foldback helps to control the output current during start-up and overload. the high voltage regulator contains a power good com- parator which trips when the hvout pin is at 2.8v. the pg output is an open-collector transistor that is off when the output is in regulation, allowing an external resistor to pull the pg pin high. power good is valid when the switching regulator is enabled and hvin is above 3.6v. ideal diode from bat to out the ltc4090/ltc4090-5 have an internal ideal diode as well as a controller for an optional external ideal diode. if a battery is the only power supply available, or if the load current exceeds the programmed input current limit, then the battery will automatically deliver power to the load via an ideal diode circuit between the bat and out pins. the ideal diode circuit (along with the recommended 4.7f capacitor on the out pin) allows the ltc4090/ltc4090-5 to handle large transient loads and wall adapter or usb v bus connect/disconnect scenarios without the need for large bulk capacitors. the ideal diode responds within a few microseconds and prevents the out pin voltage from dropping signi? cantly below the bat pin voltage. a comparison of the i-v curve of the ideal diode and a schottky diode can be seen in figure 3. if the desired input current increases beyond the pro- grammed input current limit additional current will be drawn from the battery via the internal ideal diode. furthermore, if power to in (usb v bus ) or hvin (high voltage input) is removed, then all of the application power will be pro- vided by the battery via the ideal diode. a 4.7f capacitor at out is suf? cient to keep a transition from input power to battery power from causing signi? cant output voltage droop. the ideal diode consists of a precision ampli? er that enables a large p-channel mosfet transistor whenever the voltage at out is approximately 20mv (v fwd ) below the voltage at bat. the resistance of the internal ideal diode is approximately 215m . if this is suf? cient for the application then no external components are necessary. however if more conductance is needed, an external p-channel mosfet can be added from bat to out. the gate pin of the ltc4090/ltc4090-5 drives the gate of the external pfet for automatic ideal diode control. the source of the external mosfet should be connected to out and the drain should be connected to bat. in order to help protect the external mosfet in overcurrent situations, it should be placed in close thermal contact to the ltc4090/ltc4090-5. figure 2. input and battery currents as a function of load current i in i load(ma) 0 300 400 500 400 500 300 4090 f02a 200 100 100 200 0 current (ma) i load i bat (charging) i bat (ideal diode) i in i load(ma) 0 60 80 100 80 100 60 4090 f02b 40 20 20 40 0 current (ma) i load i bat (charging) i bat (ideal diode) i load (ma) 0 300 400 500 400 500 300 4090 f02c 200 100 100 200 0 current (ma) i in i load i bat = i chg i bat = i cl = i out i bat (charging) i bat (ideal diode) (a) high power mode/full charge r prog = 100k and r clprog = 2k (b) low power mode/full charge r prog = 100k and r clprog = 2k (c) high power mode with i cl = 500ma and i chg = 250ma r prog = 100k and r clprog = 2k
ltc4090/ltc4090-5 15 4090fc operation suspend mode when susp is pulled above v ih the ltc4090/ltc4090-5 enter suspend mode to comply with the usb speci? cation. in this mode, the power path between in and out is put in a high impedance state to reduce the in input current to 50a. if no other power source is available to drive hvin, the system load connected to out is supplied through the ideal diodes connected to bat. battery charger the battery charger circuits of the ltc4090/ltc4090-5 are designed for charging single-cell lithium-ion batter- ies. featuring an internal p-channel power mosfet, the charger uses a constant-current / constant-voltage charge algorithm with programmable charge current and a pro- grammable timer for charge termination. charge current can be programmed up to 1.5a. the ? nal ? oat voltage ac- curacy is 0.8% typical. no blocking diode or sense resistor is required when powering either the in or the hvin pins. the chrg open-drain status output provides information regarding the charging status of the ltc4090/ltc4090-5 at all times. an ntc input provides the option of charge quali? cation using battery temperature. the charge cycle begins when the voltage at the out pin rises above the battery voltage and the battery volt- age is below the recharge threshold. no charge current actually ? ows until the out voltage is 100mv above the bat voltage. at the beginning of the charge cycle, if the battery voltage is below 2.9v, the charger goes into trickle charge mode to bring the cell voltage up to a safe level for charging. the charger goes into the fast charge constant-current mode once the voltage on the bat pin rises above 2.9v. in constant-current mode, the charge current is set by r prog . when the battery approaches the ? nal ? oat voltage, the charge current begins to decrease as the ltc4090/ltc4090-5 switch to constant-voltage mode. when the charge current drops below 10% of the programmed value while in constant-voltage mode the chrg pin assumes a high impedance state. an external capacitor on the timer pin sets the total minimum charge time. when this time elapses, the charge cycle terminates and the chrg pin assumes a high impedance state, if it has not already done so. while charging in constant-current mode, if the charge current is decreased by thermal regulation or in order to maintain the programmed input current limit, the charge time is automatically increased. in other words, the charge time is extended inversely proportional to the actual charge current delivered to the battery. for li-ion and similar batteries that require accurate ? nal ? oat potential, the internal bandgap reference, voltage ampli? er and the resistor divider provide regulation with 0.8% accuracy. trickle charge and defective battery detection at the beginning of a charge cycle, if the battery voltage is below 2.9v, the charger goes into trickle charge reduc- ing the charge current to 10% of the full-scale current. if the low battery voltage persists for one quarter of the programmed total charge time, the battery is assumed to be defective, the charge cycle is terminated and the chrg pin output assumes a high impedance state. if for any reason the battery voltage rises above ~2.9v the charge cycle will be restarted. to restart the charge cycle (i.e., when the dead battery is replaced with a discharged battery), simply remove the input voltage and reapply it or cycle the timer pin to 0v. programming charge current the formula for the battery charge current is: i chg = i prog ? 50,000 = v prog r prog ? 50,000 figure 3. ltc4090/ltc4090-5 vs schottky diode forward voltage drop constant i 0n constant r 0n constant v 0n v fwd i max forward voltage (v) 4090 f03 i fwd 0 current (a) slope: 1/r dio(on) slope: 1/r fwd schottky diode ltc4090/ltc4090-5
ltc4090/ltc4090-5 16 4090fc operation where v prog is the prog pin voltage and r prog is the total resistance from the prog pin to ground. keep in mind that when the ltc4090/ltc4090-5 are powered from the in pin, the programmed input current limit takes precedence over the charge current. in such a scenario, the charge current cannot exceed the programmed input current limit. for example, if typical 500ma charge current is required, calculate: r prog = 1v 500ma ? 50,000 = 100k for best stability over temperature and time, 1% metal ? lm resistors are recommended. under trickle charge conditions, this current is reduced to 10% of the full- scale value. the charge timer the programmable charge timer is used to terminate the charge cycle. the timer duration is programmed by an external capacitor at the timer pin. the charge time is typically: t timer (hours) = c timer ?r prog ? 3hours 0.1f ? 100k the timer starts when an input voltage greater than the undervoltage lockout threshold level is applied or when leaving shutdown and the voltage on the battery is less than the recharge threshold. at power-up or exiting shutdown with the battery voltage less than the recharge threshold, the charge time is a full cycle. if the battery is greater than the recharge threshold the timer will not start and charging is prevented. if after power-up the battery voltage drops below the recharge threshold, or if after a charge cycle the battery voltage is still below the recharge threshold, the charge time is set to one-half of a full cycle. the ltc4090/ltc4090-5 have a feature that extends charge time automatically. charge time is extended if the charge current in constant-current mode is reduced due to load current or thermal regulation. this change in charge time is inversely proportional to the change in charge current. as the ltc4090/ltc4090-5 approach constant-voltage mode the charge current begins to drop. this change in charge current is due to normal charging operation and does not affect the timer duration. consider, for example, a usb charge condition where r clprog = 2k, r prog = 100k and c timer = 0.1f. this corresponds to a three hour charge cycle. however, if the hpwr input is set to a logic low, then the input current limit will be reduced from 500ma to 100ma. with no ad- ditional system load, this means the charge current will be reduced to 100ma. therefore, the termination timer will automatically slow down by a factor of ? ve until the charger reaches constant-voltage mode (i.e., v bat ap- proaches 4.2v) or hpwr is returned to a logic high. the charge cycle is automatically lengthened to account for the reduced charge current. the exact time of the charge cycle will depend on how long the charger remains in constant-current mode and/or how long the hpwr pin remains logic low. once a timeout occurs and the voltage on the battery is greater than the recharge threshold, the charge current stops, and the chrg output assumes a high impedance state if it has not already done so. connecting the timer pin to ground disables the battery charger. chrg status output pin when the charge cycle starts, the chrg pin is pulled to ground by an internal n-channel mosfet capable of driv- ing an led. when the charge current drops below 10% of the programmed full charge current while in constant- voltage mode, the pin assumes a high impedance state, but charge current continues to ? ow until the charge time elapses. if this state is not reached before the end of the programmable charge time, the pin will assume a high impedance state when a timeout occurs. the chrg current detection threshold can be calculated by the fol- lowing equation: i detect = 0.1v r prog ? 50,000 = 5000v r prog
ltc4090/ltc4090-5 17 4090fc for example, if the full charge current is programmed to 500ma with a 100k prog resistor the chrg pin will change state at a battery charge current of 50ma. note: the end-of-charge (eoc) comparator that moni- tors the charge current latches its decision. therefore, the ? rst time the charge current drops below 10% of the programmed full charge current while in constant-volt- age mode, it will toggle chrg to a high impedance state. if, for some reason the charge current rises back above the threshold, the chrg pin will not resume the strong pull-down state. the eoc latch can be reset by a recharge cycle (i.e., v bat drops below the recharge threshold) or toggling the input power to the part. automatic recharge after the battery charger terminates, it will remain off drawing only microamperes of current from the battery. if the product remains in this state long enough, the battery will eventually self discharge. to ensure that the battery is always topped off, a charge cycle will automatically begin when the battery voltage falls below v rechrg (typically 4.1v). to prevent brief excursions below v rechrg from resetting the safety timer, the battery voltage must be below v rechrg for more than a few milliseconds. the charge cycle and safety timer will also restart if the in uvlo cycles low and then high (e.g., in is removed and then replaced). thermal regulation to prevent thermal damage to the ic or surrounding components, an internal thermal feedback loop will automatically decrease the programmed charge current if the die temperature rises to approximately 105c. thermal regulation protects the ltc4090/ltc4090-5 from excessive temperature due to high power operation or high ambient thermal conditions and allows the user to push the limits of the power handling capability with a given circuit board design without risk of damaging the ltc4090/ltc4090-5 or external components. the bene? t of the ltc4090/ltc4090-5 thermal regulation loop is that charge current can be set according to actual conditions rather than worst-case conditions with the assurance that the battery charger will automatically reduce the current in worst-case conditions. undervoltage lockout an internal undervoltage lockout circuit monitors the input voltage (in) and the output voltage (out) and disables either the input current limit or the battery charger circuits or both. the input current limit circuitry is disabled until v in rises above the undervoltage lockout threshold and v in exceeds v out by 50mv. the battery charger circuits are dis- abled until v out exceeds v bat by 50mv. both undervoltage lockout comparators have built-in hysteresis. ntc thermistor the battery temperature is measured by placing a nega- tive temperature coef? cient (ntc) thermistor close to the battery pack. to use this feature connect the ntc thermistor, r ntc , between the ntc pin and ground and a bias resistor, r nom , from vntc to ntc. r nom should be a 1% resistor with a value equal to the value of the chosen ntc thermistor at 25c (denoted r 25c ). the ltc4090/ltc4090-5 will pause charging when the resistance of the ntc thermistor drops to 0.41 times the value of r 25c or approximately 4.1k (for a vishay curve 2 thermistor, this corresponds to approximately 50c). the safety timer also pauses until the thermistor indicates a return to a valid temperature. as the temperature drops, the resistance of the ntc thermistor rises. the ltc4090/ ltc4090-5 are also designed to pause charging (and timer) when the value of the ntc thermistor increases to 2.82 times the value of r 25c . for a vishay curve 2 thermistor this resistance, 28.2k, corresponds to approximately 0c. the hot and cold comparators each have approximately 3c of hysteresis to prevent oscillation about the trip point. grounding the ntc pin disables all ntc functionality. operation
ltc4090/ltc4090-5 18 4090fc usb and 5v wall adapter power although the ltc4090/ltc4090-5 are designed to draw power from a usb port, a higher power 5v wall adapter can also be used to power the application and charge the battery (higher voltage wall adapters can be connected directly to hvin). figure 4 shows an example of combining a 5v wall adapter and a usb power input. with its gate grounded by 1k, p-channel mosfet mp1 provides usb power to the ltc4090/ltc4090-5 when 5v wall power is not available. when 5v wall power is available, diode d1 supplies power to the ltc4090/ltc4090-5, pulls the gate of mn1 high to increase the charge current (by increasing the input current limit), and pulls the gate of mp1 high to disable it and prevent conduction back to the usb port. setting the switching frequency the high voltage switching regulator uses a constant- frequency pwm architecture that can be programmed to switch from 200khz to 2.4mhz by using a resistor tied from the r t pin to ground. a table showing the necessary r t value for a desired switching frequency is in table 1. table 1. switching frequency vs r t value switching frequency (mhz) r t value (k ) 0.2 187 0.3 121 0.4 88.7 0.5 68.1 0.6 56.2 0.7 46.4 0.8 40.2 0.9 34.0 1.0 29.4 1.2 23.7 1.4 19.1 1.6 16.2 1.8 13.3 2.0 11.5 2.2 9.76 2.4 8.66 applications information figure 4. usb or 5v wall adapter power operating frequency trade-offs selection of the operating frequency for the high voltage buck regulator is a trade-off between ef? ciency, compo- nent size, minimum dropout voltage, and maximum input voltage. the advantage of high frequency operation is that smaller inductor and capacitor values may be used. the disadvantages are lower ef? ciency, lower maximum input voltage, and higher dropout voltage. the highest acceptable switching frequency (f sw(max) ) for a given application can be calculated as follows: f sw(max) = v d + v hvout t on(min) ?v d + v hvin ?v sw () where v hvin is the typical high voltage input voltage, v hvout is the output voltage of the switching regulator, v d is the catch diode drop (~0.5v), and v sw is the internal switch drop (~0.5v at max load). this equation shows that slower switching frequency is necessary to safely accommodate high v hvin /v hvout ratio. also, as shown in the next section, lower frequency allows a lower dropout voltage. the reason input voltage range depends on the switching frequency is because the high voltage switch has ? nite minimum on and off times. the switch can turn on for a minimum of ~150ns and turn off for a minimum of ~150ns. this means that the minimum and maximum duty cycles are: dc min = f sw ? t on(min) dc max = 1 C f sw ? t off(min) where f sw is the switching frequency, t on(min) is the minimum switch-on time (~150ns), and t off(min) is the 2k 1k mn1 2.87k 59k in prog clprog ltc4090 bat + mp1 d1 i chg li-ion battery 5v wall adapter 850ma i chg usb power 500ma i chg 4090 f04
ltc4090/ltc4090-5 19 4090fc applications information minimum switch-off time (~150ns). these equations show that duty cycle range increases when switching frequency is decreased. a good choice of switching frequency should allow ad- equate input voltage range (see next section) and keep the inductor and capacitor values small. hvin input voltage range the maximum input voltage range for the ltc4090/ ltc4090-5 applications depends on the switching fre- quency, the absolute maximum ratings of the v hvin and boost pins, and the operating mode. the high voltage switching regulator can operate from input voltages up to 36v, and safely withstand input volt- ages up to 60v. note that while v hvin > 38v (typical), the ltc4090/ltc4090-5 will stop switching, allowing the output to fall out of regulation. while the high voltage regulator output is in start-up, short-circuit, or other overload conditions, the switching frequency should be chosen according to the following discussion. for safe operation at inputs up to 60v the switching fre- quency must be low enough to satisfy v hvin(max) 40v according to the following equation. if lower v hvin(max) is desired, this equation can be used directly. v hvin(max) = v hvout + v d f sw ?t on(min) ?v d + v sw where v hvin(max) is the maximum operating input voltage, v hvout is the high voltage regulator output voltage, v d is the catch diode drop (~0.5v), v sw is the internal switch drop (~0.5v at max load), f sw is the switching frequency (set by r t ), and t on(min) is the minimum switch-on time (~150ns). note that a higher switching frequency will de- press the maximum operating input voltage. conversely, a lower switching frequency will be necessary to achieve safe operation at high input voltages. if the output is in regulation and no short-circuit, start- up, or overload events are expected, then input voltage transients of up to 60v are acceptable regardless of the switching frequency. in this mode, the ltc4090/ltc4090-5 may enter pulse-skipping operation where some switch- ing pulses are skipped to maintain output regulation. in this mode the output voltage ripple and inductor current ripple will be higher than in normal operation. above 38v, switching will stop. the minimum input voltage is determined by either the high voltage regulators minimum operating voltage of ~6v or by its maximum duty cycle (see equation in previous section). the minimum input voltage due to duty cycle is: v hvin(min) = v hvout + v d 1 ? f sw t off(min) ? v d + v sw where v hvin(min) is the minimum input voltage, and t off(min) is the minimum switch-off time (150ns). note that higher switching frequency will increase the minimum input voltage. if a lower dropout voltage is desired, a lower switching frequency should be used. inductor selection and maximum output current a good choice for the inductor value is l = 6.8h (assum- ing a 800khz operating frequency). with this value the maximum load current will be ~2.4a. the rms current rating of the inductor must be greater than the maximum load current and its saturation current should be about 30% higher. note that the maximum load current will be programmed charge current plus the largest expected application load current. for robust operation in fault conditions, the saturation current should be ~3.5a. to keep ef? ciency high, the series resistance (dcr) should be less than 0.1 . table 2 lists several vendors and types that are suitable. table 2. inductor vendors vendor url part series type murata www.murata.com lqh55d open tdk www.componenttdk.com slf7045 slf10145 shielded shielded toko www.toko.com d62cb d63cb d75c d75f shielded shielded shielded open sumida www.sumida.com cr54 cdrh74 cdrh6d38 cr75 open shielded shielded open
ltc4090/ltc4090-5 20 4090fc applications information catch diode the catch diode conducts current only during switch-off time. average forward current in normal operation can be calculated from: i d(avg) = i hvout ? v hvin ?v hvout () v hvin where i hvout is the output load current. the only reason to consider a diode with a larger current rating than necessary for nominal operation is for the worst-case condition of shorted output. the diode current will then increase to the typical peak switch current. peak reverse voltage is equal to the regulator input voltage. use a schottky diode with a reverse voltage rating greater than the input voltage. the overvoltage protection feature in the high voltage regulator will keep the switch off when v hvin > 40v which allows the use of 40v rated schottky even when v hvin ranges up to 60v. table 3 lists several schottky diodes and their manufacturers. table 3. diode vendors part number v r (v) i ave (a) v f at 1a (mv) v f at 2a (mv) on semiconductor mbrm120e mbrm140 20 40 1 1 530 550 595 diodes inc. b120 b130 b220 b230 dfls240l 20 30 20 30 40 1 1 2 2 2 500 500 500 500 500 international recti? er 10bq030 20bq030 30 30 1 2 420 470 470 high voltage regulator output capacitor selection the high voltage regulator output capacitor has two es- sential functions. along with the inductor, it ? lters the square wave generated at the switch pin to produce the dc output. in this role it determines the output ripple, and low impedance at the switching frequency is important. the second function is to store energy in order to satisfy transient loads and stabilize the ltc4090/ltc4090-5s control loop. ceramic capacitors have very low equiva- lent series resistance (esr) and provide the best ripple performance. a good starting value is: c out = 100 v out f sw where f sw is in mhz, and c out is the recommended output capacitance in f. use x5r or x7r types. this choice will provide low output ripple and good transient response. transient performance can be improved with a higher value capacitor if the compensation network is also adjusted to maintain the loop bandwidth. a lower value of output capacitor can be used to save space and cost but transient performance will suffer. see the high voltage regulator frequency compensation section to choose an appropriate compensation network. when choosing a capacitor, look carefully through the data sheet to ? nd out what the actual capacitance is under operating conditions (applied voltage and temperature). a physically larger capacitor, or one with a higher voltage rating, may be required. high performance tantalum or electrolytic capacitors can be used for the output capacitor. low esr is important, so choose one that is intended for use in switching regulators. the esr should be speci? ed by the supplier, and should be 0.05 or less. such a capacitor will be larger than a ceramic capacitor and will have a larger capacitance, because the capacitor must be large to achieve low esr. ceramic capacitors ceramic capacitors are small, robust and have very low esr. however, ceramic capacitors can cause problems when used with the high voltage switching regulator due to their piezoelectric nature. when in burst mode operation, the ltc4090/ltc4090-5s switching frequency depends on the load current, and at very light loads the ltc4090/ltc4090-5 can excite the ceramic capacitor at audio frequencies, generating audible noise. since the ltc4090/ltc4090-5 operate at a lower current limit during burst mode operation, the noise is typically very quiet to a casual ear. if this is unacceptable, use a high performance tantalum or electrolytic capacitor at the output.
ltc4090/ltc4090-5 21 4090fc figure 5. transient load response of the ltc4090 high voltage regulator front page application as the load current is stepped from 500ma to 1500ma. figure 6. high voltage regulator burst mode operation high voltage regulator frequency compensation the ltc4090/ltc4090-5 high voltage regulator uses current mode control to regulate the output. this simpli- ? es loop compensation. in particular, the high voltage regulator does not require the esr of the output capacitor for stability, so you are free to use ceramic capacitors to achieve low output ripple and small circuit size. frequency compensation is provided by the components tied to the v c pin, as shown in figure 1. generally a capacitor (c c ) and a resistor (r c ) in series to ground are used. in ad- dition, there may be a lower value capacitor in parallel. this capacitor (c f ) is not part of the loop compensation but is used to ? lter noise at the switching frequency, and is required only if a phase-lead capacitor is used or if the output capacitor has high esr. loop compensation determines the stability and transient performance. designing the compensation network is a bit complicated and the best values depend on the application and in particular the type of output capacitor. a practical approach is to start with the front page schematic and tune the compensation network to optimize performance. stabil- ity should then be checked across all operating conditions, including load current, input voltage and temperature. the ltc1375 data sheet contains a more thorough discussion of loop compensation and describes how to test the sta- bility using a transient load. figure 5 shows the transient response when the load current is stepped from 500ma to 1500ma and back to 500ma. low ripple burst mode operation and pulse-skipping mode the ltc4090/ltc4090-5 are capable of operating in either low ripple burst mode operation or pulse-skipping mode which are selected using the sync pin. tie the sync pin below v sync,l (typically 0.5v) for low ripple burst mode operation or above v sync,h (typically 0.8v) for pulse- skipping mode. to enhance ef? ciency at light loads, the ltc4090/ltc4090-5 can be operated in low ripple burst mode operation which keeps the output capacitor charged to the proper voltage while minimizing the input quiescent current. during burst mode operation, the ltc4090/ltc4090-5 deliver single cycle bursts of current to the output capacitor followed by sleep periods where the output power is delivered to the load by the output capacitor. because the ltc4090/ ltc4090-5 deliver power to output with single, low current pulses, the output ripple is kept below 15mv for a typical application. as the load current decreases towards a no load condition, the percentage of time that the high volt- age regulator operates in sleep mode increases and the average input current is greatly reduced resulting in high ef? ciency even at very low loads. see figure 6. at higher output loads (above 70ma for the front page application) the ltc4090/ltc4090-5 will be running at the frequency programmed by the r t resistor, and will be operating in standard pwm mode. the transition between pwm and low ripple burst mode operation is seamless, and will not disturb the output voltage. applications information 25s/div hvout 50mv/div i l 1a/div 4090 f05 figure 12 schematic 4090 f06 i l 0.5a/div v sw 5v/div v out 10mv/div 5s/div v in = 12v; figure 12 schematic i load = 10ma
ltc4090/ltc4090-5 22 4090fc if low quiescent current is not required, the ltc4090/ ltc4090-5 can operate in pulse-skipping mode. the bene? t of this mode is that the ltc4090/ltc4090-5 will enter full frequency standard pwm operation at a lower output load current than when in burst mode operation. the front page application circuit will switch at full frequency at output loads higher than about 60ma. boost pin considerations capacitor c2 (see block diagram) and an internal diode are used to generate a boost voltage that is higher than the input voltage. in most cases, a 0.47f capacitor will work well. the boost pin must be at least 2.3v above the sw pin for proper operation. high voltage regulator soft-start the hven pin can be used to soft-start the high voltage regulator of the ltc4090/ltc4090-5, reducing maximum input current during start-up. the hven pin is driven through an external rc ? lter to create a voltage ramp at this pin. figure 7 shows the start-up and shutdown wave- forms with the soft-start circuit. by choosing a large rc time constant, the peak start-up current can be reduced to the current that is required to regulate the output, with no overshoot. choose the value of the resistor so that it can supply 20a when the hven pin reaches 2.3v. synchronization and mode the sync pin allows the high voltage regulator to be synchronized to an external clock. synchronizing the ltc4090/ltc4090-5 internal oscillator to an external frequency can be done by connecting a square wave (with 20% to 80% duty cycle) to the sync pin. the square wave amplitude should be such that the valleys are below 0.3v and the peaks are above 0.8v (up to 6v). the high voltage regulator may be synchronized over a 300khz to 2mhz range. the r t resistor should be chosen such that the ltc4090/ltc4090-5 oscillate 25% lower than the external synchronization frequency to ensure adequate slope compensation. while synchronized, the high voltage regulator will turn on the power switch on positive going edges of the clock. when the power good (pg) output is low, such as during start-up, short-circuit, and overload conditions, the ltc4090/ltc4090-5 will dis- able the synchronization feature. the sync pin should be grounded when synchronization is not required. alternate ntc thermistors and biasing the ltc4090/ltc4090-5 provide temperature quali? ed charging if a grounded thermistor and a bias resistor are connected to ntc (see figure 8). by using a bias resistor whose value is equal to the room temperature resistance of the thermistor (r 25c ) the upper and lower temperatures are preprogrammed to approximately 50c and 0c, re- spectively (assuming a vishay curve 2 thermistor). the upper and lower temperature thresholds can be ad- justed by either a modi? cation of the bias resistor value or by adding a second adjustment resistor to the circuit. if only the bias resistor is adjusted, then either the upper or the lower threshold can be modi? ed but not both. the other trip point will be determined by the characteristics of the thermistor. using the bias resistor in addition to an adjustment resistor, both the upper and the lower tempera- ture trip points can be independently programmed with the constraint that the difference between the upper and lower temperature thresholds cannot decrease. examples of each technique are given below. ntc thermistors have temperature characteristics which are indicated on resistance-temperature conversion tables. the vishay-dale thermistor nths0603n02n1002j, used in the following examples, has a nominal value of 10k and follows the vishay curve 2 resistance-temperature characteristic. the ltc4090/ltc4090-5s trip points are applications information figure 7. to soft-start the high voltage regulator, add a resistor and capacitor to the hven pin 4090 f07 i l 1a/div hven 2v/div v out 2v/div hven gnd 0.22f run 15k 2ms/div
ltc4090/ltc4090-5 23 4090fc designed to work with thermistors whose resistance-tem- perature characteristics follow vishay dales r-t curve 2. the vishay nths0603n02n1002j is an example of such a thermistor. however, vishay dale has many thermistor products that follow the r-t curve 2 characteristic in a variety of sizes. furthermore, any thermistor whose ratio of r cold to r hot is about 7.0 will also work (vishay dale r-t curve 2 shows a ratio of 2.815/0.409 = 6.89). in the explanation below, the following notation is used. r 25c = value of the thermistor at 25c r ntc|cold = value of thermistor at the cold trip point r ntc|hot = value of the thermistor at the hot trip point r cold = ratio of r ntc|cold to r 25c r hot = ratio of r ntc|hot to r 25c r nom = primary thermistor bias resistor (see figure 8) r1 = optional temperature range adjustment resistor (see figure 9) the trip points for the ltc4090/ltc4090-5s tempera- ture quali? cation are internally programmed at 0.29 ? vntc for the hot threshold and 0.74 ? vntc for the cold threshold. therefore, the hot trip point is set when: r ntc|hot r nom + r ntc|hot ?vntc = 0.29 ? vntc and the cold trip point is set when: r ntc|cold r nom + r ntc|cold ?vntc = 0.74 ? vntc solving these equations for r ntc|cold and r ntc|hot results in the following: r ntc|hot = 0.409 ? r nom and r ntc|cold = 2.815 ? r nom by setting r nom equal to r 25c , the above equations result in r hot = 0.409 and r cold = 2.815. referencing these ratios to the vishay resistance-temperature curve 2 chart gives a hot trip point of about 50c and a cold trip point of about 0c. the difference between the hot and cold trip points is approximately 50c. by using a bias resistor, r nom , different in value from r 25c , the hot and cold trip points can be moved in either direction. the temperature span will change somewhat due to the nonlinear behavior of the thermistor. the following applications information figure 8. typical ntc thermistor circuit figure 9. ntc thermistor circuit with additional bias resistor C + C + r nom 10k r ntc 10k ntc vntc 6 0.1v ntc_enable 4090 f08 ntc block too_cold too_hot 0.738 ? vntc 0.29 ? vntc C + 5 C + C + r nom 13.2k r ntc 10k r1 1.97k ntc vntc 6 0.1v ntc_enable 4090 f09 too_cold too_hot 0.738 ? vntc 0.29 ? vntc C + 5 ntc block
ltc4090/ltc4090-5 24 4090fc equations can be used to easily calculate a new value for the bias resistor: r nom = r hot 0.409 ?r 25c r nom = r cold 2.815 ?r 25c where r hot and r cold are the resistance ratios at the de- sired hot and cold trip points. note that these equations are linked. therefore, only one of the two trip points can be chosen, the other is determined by the default ratios designed in the ic. consider an example where a 40c hot trip point is desired. from the vishay curve 2 r-t characteristics, r hot is 0.5758 at 40c. using the above equation, r nom should be set to 14.0k. with this value of r nom , the cold trip point is about C7c. notice that the span is now 47c rather than the pre- vious 50c. this is due to the increase in temperature gain of the thermistor as absolute temperature decreases. the upper and lower temperature trip points can be inde- pendently programmed by using an additional bias resistor as shown in figure 9. the following formulas can be used to compute the values of r nom and r1: r nom = r cold ?r hot 2.815 ?r 25c r1 = 0.409 ? r nom ?r hot ?r 25c for example, to set the trip points to C5c and 55c with a vishay curve 2 thermistor choose r nom = 3.532 ? 0.3467 2.815 ? 0.409 ?10k = 13.2k the nearest 1% value is 13.3k. r1 = 0.409 ? 13.3k C 0.3467 ? 10k = 1.97k the nearest 1% value is 1.96k. the ? nal solution is shown in figure 9 and results in an upper trip point of 55c and a lower trip point of C5c. power dissipation and high temperature considerations the die temperature of the ltc4090/ltc4090-5 must be lower than the maximum rating of 110c. this is generally not a concern unless the ambient temperature is above 85c. the total power dissipated inside the ltc4090/ ltc4090-5 depend on many factors, including input voltage (in or hvin), battery voltage, programmed charge current, programmed input current limit, and load current. in general, if the ltc4090/ltc4090-5 is being powered from in the power dissipation can be calculated as follows: p d = (v in C v bat ) ? i bat + (v in C v out ) ? i out where p d is the power dissipated, i bat is the battery charge current, and i out is the application load current. for a typical application, an example of this calculation would be: p d = (5v C 3.7v) ? 0.4a + (5v C 4.75v) ? 0.1a = 545mw this examples assumes v in = 5v, v out = 4.75v, v bat = 3.7v, i bat = 400ma, and i out = 100ma resulting in slightly more than 0.5w total dissipation. if the ltc4090 is being powered from hvin, the power dissipation can be estimated by calculating the regulator power loss from an ef? ciency measurement, and subtract- ing the catch diode loss. p d = (1 ? )? v hvout ?(i bat + i out ) ? ? ? ? ? v d ?1 ? v hvout v hvin ? ? ? ? ? ? ?i bat + i out ) + 0.3v ?i bat () where is the ef? ciency of the high voltage regulator and v d is the forward voltage of the catch diode at i = i bat + i out . the ? rst term corresponds to the power lost in converting v hvin to v hvout , the second term subtracts the catch diode loss, and the third term is the power dis- sipated in the battery charger. for a typical application, an example of this calculation would be: p d = (1 ? 0.87) ? 4v ? (1a + 0.6a) [] ? 0.4v ? 1 ? 4v 12v ? ? ? ? ? ? ?1a + 0.6a () + 0.3v ? 1a = 0.7w this example assumes 87% ef? ciency, v hvin = 12v, v bat = 3.7v (v hvout is about 4v), i bat = 1a, i out = 600ma resulting in about 0.7w total dissipation. if the ltc4090-5 is being powered from hvin, the power dissipation can applications information
ltc4090/ltc4090-5 25 4090fc figure 10. suggested board layout be estimated by calculating the regulator power loss from an ef? ciency measurement, and subtracting the catch diode loss. p d = 1? () ?5v?i bat + i out () () ?v d ?1? 5v v hvin ? ? ? ? ? ? ? i bat + i out () + 5v ? v bat () ?i bat the difference between this equation and that for the ltc4090 is the last term, which represents the power dissipation in the battery charger. for a typical application, an example of this calculation would be: p d = 1? 0.87 () ?5v?1a + 0.6a () () ? 0.4v ? 1? 5v 12v ? ? ? ? ? ? ? 1a + 0.6a () + 5v ? 3.7v () ?1a = 1.97w like the ltc4090 example, this examples assumes 87% ef? ciency, v hvin = 12v, v bat = 3.7v, i bat = 1a and i out = 600ma resulting in about 2w total power dissipation. it is important to solder the exposed backside of the pack- age to a ground plane. this ground should be tied to other copper layers below with thermal vias; these layers will spread the heat dissipated by the ltc4090/ltc4090-5. additional vias should be placed near the catch diode. adding more copper to the top and bottom layers and tying this copper to the internal planes with vias can reduce thermal resistance further. with these steps, the thermal resistance from die (i.e., junction) to ambient can be reduced to ja = 40c/w. board layout considerations as discussed in the previous section, it is critical that the exposed metal pad on the backside of the ltc4090/ ltc4090-5 package be soldered to the pc board ground. furthermore, proper operation and minimum emi requires a careful printed circuit board (pcb) layout. note that large, switched currents ? ow in the power switch (between the hvin and sw pins), the catch diode and the hvin input capacitor. these components, along with the inductor and output capacitor, should be placed on the same side of the circuit board, and their connections should be made on that layer. place a local, unbroken ground plane below these components. the loop formed by these components should be as small as possible. additionally, the sw and boost nodes should be kept as small as possible. figure 10 shows the recommended component placement with trace and via locations. high frequency currents, such as the high voltage input current of the ltc4090/ltc4090-5, tend to ? nd their way along the ground plane on a mirror path directly beneath the incident path on the top of the board. if there are slits or cuts in the ground plane due to other traces on that layer, the current will be forced to go around the slits. if high frequency currents are not allowed to ? ow back through their natural least-area path, excessive voltage will build up and radiated emissions will occur. see figure 11. applications information c1 and d1 gnd pads side-by-side and seperated with c3 gnd pad u1 thermal pad soldered to pcb. vias connected to all gnd planes without thermal relief minimize d1, l1, c3, u1, sw pin loop minimize trace length 4090 f10 figure 11. ground currents follow their incident path at high speed. slices in the ground plane cause high voltage and increased emissions. 4090 f11
ltc4090/ltc4090-5 26 4090fc figure 12. 800khz switching frequency hvin hven in hpwr v c susp timer clprog prog r t pg sync sw high (7.5v to 36v) voltage input l1 6.8h 4090 f12 ltc4090 boost hvout hvpr out gate bat vntc ntc chrg c1 1f 50v 1206 0.1f 2.1k 1% 71.5k 1% 40.2k 1% 59k 1% 680 0.47f 16v d1 c3 22f 6.3v 1206 4.7f 6.3v 270pf li-ion battery 680 d: diodes inc. b360a l: sumida cdr6d28mn-gr5 q1, q2: siliconix si2333ds 1k 10k 1% q1 q2 10k t load + usb 4.7f 6.3v hvin boost in sw 4.7f 4.7f q1 4.7f 1f timer clprog ltc4090 gnd prog hvout hvpr out bat 0.1f 330pf 71.5k 2.1k l: sumida cdrh8d28/hp-100 * use schottky diode rated at v r > 45v usb high (7.5v to 36v) transient to 60v* v c r t 88.7k 35k li-ion battery + 1k l 10h load 4090 tao3 0.47f hvin boost in sw 4.7f 22f q1 4.7f 1f timer clprog ltc4090 gnd prog hvout hvpr out bat 0.1f 330pf 71.5k 2.1k l: sumida cdrh4d22/hp-2r2 usb high (7.5v to 16v) voltage input v c r t 11.5k 30k li-ion battery + 1k load 4090 tao4 l 2.2h 0.47f figure 13. 400khz switching frequency figure 14. 2mhz switching frequency in and hvin bypass capacitor many types of capacitors can be used for input bypassing; however, caution must be exercised when using multilayer ceramic capacitors. because of the self-resonant and high q characteristics of some types of ceramic capacitors, high voltage transients can be generated under some start-up conditions, such as from connecting the charger input to a hot power source. for more information, refer to application note 88. battery charger stability considerations the constant-voltage mode feedback loop is stable without any compensation when a battery is connected with low impedance leads. excessive lead length, however, may add enough series inductance to require a bypass capacitor of at least 1f from bat to gnd. furthermore, a 4.7f capacitor with a 0.2 to 1 series resistor to gnd is recommended at the bat pin to keep ripple voltage low when the battery is disconnected. applications information typical applications
ltc4090/ltc4090-5 27 4090fc information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. package description djc package 22-lead plastic dfn (6mm 3mm) (reference ltc dwg # 05-08-1714) 3.00 0.10 (2 s ide s ) note: 1. drawing propo s ed to be made variation of ver s ion (wxxx) in jedec package outline m0-229 2. drawing not to s cale 3. all dimen s ion s are in millimeter s 4. dimen s ion s of expo s ed pad on bottom of package do not include mold fla s h. mold fla s h, if pre s ent, s hall not exceed 0.15mm on any s ide 5. expo s ed pad s hall be s older plated 6. s haded area i s only a reference for pin 1 location on top and bottom of package note: 1. dimen s ion s are in millimeter s 2. apply s older ma s k to area s that are not s oldered 3. drawing i s not to s cale 0.40 0.05 pin #1 notch r0.30 typ or 0.25mm 45 chamfer bottom view?expo s ed pad 1.65 0.10 (2 s ide s ) 0.75 0.05 r = 0.115 typ r = 0.10 typ 1 22 12 11 pin 1 top mark (note 6) 0.200 ref 0.00 ? 0.05 (djc) dfn 0605 6.00 0.10 (2 s ide s ) 0.25 0.05 0.889 0.889 0.50 b s c 5.35 0.10 (2 s ide s ) r = 0.10 recommended s older pad pitch and dimen s ion s 1.65 0.05 (2 s ide s ) 2.20 0.05 0.70 0.05 3.60 0.05 package outline 0.25 0.05 0.50 b s c 5.35 0.05 (2 s ide s ) 0.889 0.889
ltc4090/ltc4090-5 28 4090fc linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2007 lt 0209 rev c ? printed in usa related parts part number description comments battery chargers ltc1733 monolithic lithium-ion linear battery charger standalone charger with programmable timer, up to 1.5a charge current ltc1734 lithium-ion linear battery charger in thinsot? simple thinsot charger, no blocking diode, no sense resistor needed ltc4002 switch mode lithium-ion battery charger standalone, 4.7v v in 24v, 500khz frequency, three-hour charge termination ltc4053 usb compatible monolithic li-ion battery charger standalone charger with programmable timer, up to 1.25a charge current ltc4054 standalone linear li-ion battery charger with integrated pass transistor in thinsot thermal regulation prevents overheating, c/10 termination, c/10 indicator, up to 800ma charge current ltc4057 lithium-ion linear battery charger up to 800ma charge current, thermal regulation, thinsot package ltc4058 standalone 950ma lithium-ion charger in dfn c/10 charge termination, battery kelvin sensing, 7% charge accuracy ltc4059 900ma linear lithium-ion battery charger 2mm 2mm dfn package, thermal regulation, charge current monitor output ltc4065/ltc4065a standalone li-ion battery chargers in 2mm 2mm dfn 4.2v, 0.6% float voltage, up to 750ma charge current, 2mm 2mm dfn, a version has acpr function. ltc4095 standalone usb lithium-ion/polymer battery charger in in 2mm 2mm dfn 950ma charge current, timer termination + c/10 detection output, 4.2v, 0.6% accurate float voltage, four chrg pin indicator states power management ltc3406/ltc3406a 600ma (i out ), 1.5mhz, synchronous step-down dc/dc converter 95% ef? ciency, v in : 2.5v to 5.5v, v out = 0.6v, i q = 20a, i sd < 1a, thinsot package ltc3411 1.25a (i out ), 4mhz, synchronous step-down dc/dc converter 95% ef? ciency, v in : 2.5v to 5.5v, v out = 0.8v, i q = 60a, i sd < 1a, ms10 package ltc3440 600ma (i out ), 2mhz, synchronous buck-boost dc/dc converter 95% ef? ciency, v in : 2.5v to 5.5v, v out = 2.5v, i q = 25a, i sd < 1a, ms package ltc3455 dual dc/dc converter with usb power manager and li-ion battery charger seamless transition between power sources: usb, wall adapter and battery; 95% ef? cient dc/dc conversion lt3493 1.2a, 750khz step-down switching regulator 88% efficiency, v in : 3.6v to 36v (40v maximum), v out = 0.8v, i sd < 2a, 2mm 3mm dfn package ltc4055 usb power controller and battery charger charges single-cell li-ion batteries directly from a usb port, thermal regulation, 200m ideal diode, 4mm 4mm qfn16 package ltc4066 usb power controller and li-ion battery charger with low loss ideal diode charges single-cell li-ion batteries directly from a usb port, thermal regulation, 50m ideal diode, 4mm 4mm qfn24 package ltc4067 usb power controller with ovp , ideal diode and li-ion battery charger 13v overvoltage transient protection, thermal regulation, 200m ideal diode with <50m option, 4mm 3mm dfn-14 package ltc4085 usb power manager with ideal diode controller and li-ion charger charges single-cell li-ion batteries directly from a usb port, thermal regulation, 200m ideal diode with <50m option, 4mm 3mm dfn14 package ltc4089/ ltc4089-5 usb power manager with ideal diode controller and high ef? ciency li-ion battery charger high ef? ciency 1.2a charger from 6v to 36v (40v max) input charges single-cell li-ion batteries directly from a usb port, thermal regulation, 200m ideal diode with <50m option, bat-track adaptive output control (ltc4089), fixed 5v output (ltc4089-5), 6mm 3mm dfn-22 package ltc4411/ltc4412 low loss powerpath controller in thinsot automatic switching between dc sources, load sharing, replaces oring diode ltc4412hv high voltage power path controllers in thinsot v in : 3v to 36v, more ef? cient than diode oring, automatic switching between dc sources, simpli? ed load sharing, thinsot package. thinsot is a trademark of linear technology corporation.

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