View AAT1112ITP-06-T1_1035319.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

aat1112 1.5a, 1.4mhz step-down converter 1112.2007.01.1.1 1 switchreg ? general description the aat1112 switchreg is a 1.5a step-down con- verter with an input voltage range of 2.4v to 5.5v and an adjustable output voltage from 0.6v to v in . the 1.4mhz switching frequency enables the use of small external components. the small footprint and high efficiency make the aat1112 an ideal choice for portable applications. the aat1112 delivers 1.5a maximum output current while consuming only 42a of no-load quiescent current. ultra-low r ds(on) integrated mosfets and 100% duty cycle operation make the aat1112 an ideal choice for high output voltage, high current applications which require a low dropout threshold. the aat1112 provides excellent transient response and high output accuracy across the operating range. no external compensation com- ponents are required. the aat1112 is designed to maintain high efficien- cy throughout the load range. pulling the mode/ sync pin high enables "pwm only" mode, main- taining constant frequency and low output ripple across the operating range. alternatively, the con- verter may be synchronized to an external clock input via the mode/sync pin. over-temperature and short-circuit protection safeguard the aat1112 and system components from damage. the aat1112 is available in a pb-free, space-sav- ing tdfn33-12 or 2.75x3mm tsopjw-12 pack- age. the product is rated over an operating tem- perature range of -40c to +85c. features ? 1.5a maximum output current ? input voltage: 2.4v to 5.5v ? output voltage: 0.6v to v in ? up to 95% efficiency ? 42a no load quiescent current ? no external compensation required ? 1.4mhz switching frequency ? synchronizable to external clock ? optional "pwm only" low noise mode ? 100% duty cycle low-dropout operation ? internal soft start ? over-temperature and current limit protection ? <1a shutdown current ? tsopjw-12 or tdfn33-12 package ? temperature range: -40c to +85c applications ? cellular phones ? digital cameras ? hard disk drives ? mp3 players ? pdas and handheld computers ? portable media players ? usb devices typical application vp gnd pgnd lx fb v out = 3.3v v in c 10f 2 c 22f 1 l 3.3h 1 en r 267k 1 r 59k 2 vin aat1112 mode/sync
aat1112 1.5a, 1.4mhz step-down converter 2 1112.2007.01.1.1 pin descriptions pin configuration tsopjw-12 tdfn33-12 (top view) (top view) pin # tsopjw-12 tdfn33-12 symbol function 1 12 lx switching node. connect the output inductor to this pin. the switching node is internally connected to the drain of both high- and low-side mosfets. 2 11 vp input voltage for the power switches. 3 10 n/c not connected. 4 9 mode/sync connect to ground for pfm/pwm mode and optimized efficien- cy throughout the load range. connect high for low noise pwm operation under all operating conditions. connect to an external clock for synchronization (pwm only). 5 8 en enable pin. a logic low disables the converter and it con- sumes less than 1a of current. when connected high, it resumes normal operation. 6 7 vin power supply. supplies power for the internal circuitry. 7 6 fb feedback input pin. this pin is connected either directly to the converter output or to an external resistive divider for an adjustable output. 8, 9, 10, 11 4, 5 gnd non-power signal ground pin. 12 1, 2, 3 pgnd main power ground return pin. connect to the output and input capacitor return. n/a ep exposed paddle (bottom); connect to ground as closely as possible to the device. 1 2 3 4 5 6 12 11 10 9 8 7 lx vp n/c mode/sync en vin pgnd gnd gnd gnd gnd fb pgnd pgnd pgnd 1 gnd gnd fb lx vp n/c mode/sync en vin 2 3 4 5 6 12 11 10 9 8 7
aat1112 1.5a, 1.4mhz step-down converter 1112.2007.01.1.1 3 absolute maximum ratings 1 thermal information symbol description value units p d maximum power dissipation tsopjw-12 0.625 tdfn33-12 2.0 w ja thermal resistance 2 tsopjw-12 160 c/w tdfn33-12 50 symbol description value units v in vin, vp to gnd 6.0 v v lx lx pin to gnd -0.3 to v in + 0.3 v v fb fb pin to gnd -0.3 to v in + 0.3 v v n mode/sync, en to gnd -0.3 to 6.0 v t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at c ondi- tions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one time. 2. mounted on an fr4 board.
aat1112 1.5a, 1.4mhz step-down converter 4 1112.2007.01.1.1 electrical characteristics 1 v in = 3.6v; t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c. symbol description conditions min typ max units v in input voltage 2.4 5.5 v v out output voltage range 0.6 v in v v in rising 2.4 v v uvlo uvlo threshold hysteresis 250 mv v in falling 1.8 v v out output voltage tolerance i out = 0a to 1.5a, -3.0 3.0 % v in = 2.4v to 5.5v i q quiescent current no load 42 90 a i shdn shutdown current v en = gnd 1.0 a i lim current limit 1.8 a r ds(on)h high side switch on-resistance 0.120 r ds(on)l low side switch on-resistance 0.085 i lxleak lx leakage current v in = 5.5v, v lx = 0 to v in 1.0 a i lxlk, r lx reverse leakage current v in unconnected, v lx = 5.5v, 1.0 a v en = gnd v loadreg load regulation i load = 0a to 1.5a 0.5 % v linereg / v in line regulation v in = 2.4v to 5.5v 0.2 %/v v fb feedback threshold voltage no load, t a = 25c 0.591 0.60 0.609 v accuracy (adjustable version) i fb fb leakage current v out = 1.0v 0.2 a f osc internal oscillator frequency 1.12 1.4 1.68 mhz synchronous clock 0.60 3.0 t s start-up time from enable to output 150 s regulation t sd over-temperature shutdown 140 c threshold t hys over-temperature shutdown 15 c hysteresis en v il enable threshold low 0.6 v v ih enable threshold high 1.4 v i en enable leakage current v in = v en = 5.5v -1.0 1.0 a mode/sync v mode/sync(l) enable threshold low 0.6 v v mode/sync(h) enable threshold high 1.4 v i mode/sync enable leakage current v in = v en = 5.5v -1.0 1.0 a 1. the aat1112 is guaranteed to meet performance specifications over the -40c to +85c operating temperature range and is assu red by design, characterization, and correlation with statistical process controls.
aat1112 1.5a, 1.4mhz step-down converter 1112.2007.01.1.1 5 typical characteristics load regulation (pfm mode; v out = 2.5v) output current (ma) v out error (%) -0.50 -0.25 0.00 0.25 0.50 0.1 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 4.2v efficiency vs. output current (pfm mode; v out = 2.5v) output current (ma) efficiency (%) 50 60 70 80 90 100 0.1 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 4.2v load regulation (pwm mode; v out = 3.3v) output current (ma) v out error (%) -0.50 -0.25 0.00 0.25 0.50 0.1 1 10 100 1000 10000 v in = 3.6v v in = 5.0v v in = 4.2v efficiency vs. output current (pwm mode; v out = 3.3v) output current (ma) efficiency (%) 0 20 40 60 80 100 1.0 10 100 1000 10000 v in = 3.6v v in = 4.2v v in = 5.0v load regulation (pfm mode; v out = 3.3v) output current (ma) v out error (%) -0.50 -0.25 0.00 0.25 0.50 0.1 1 10 100 1000 10000 v in = 3.6v v in = 4.2v v in = 5.0v efficiency vs. output current (pfm mode; v out = 3.3v) output current (ma) efficiency (%) 40 50 60 70 80 90 100 0.1 1 10 100 1000 10000 v in = 4.2v v in = 3.6v v in = 5.0v
aat1112 1.5a, 1.4mhz step-down converter 6 1112.2007.01.1.1 typical characteristics load regulation (pwm mode; v out = 1.8v) output current (ma) v out error (%) -0.50 -0.25 0.00 0.25 0.50 0.1 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 4.2v efficiency vs. output current (pwm mode; v out = 1.8v) output current (ma) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 4.2v load regulation (pfm mode; v out = 1.8v) output current (ma) v out error (%) -0.50 -0.25 0.00 0.25 0.50 0.1 1 10 100 1000 v in = 3.6v v in = 2.7v v in = 4.2v efficiency vs. output current (pfm mode; v out = 1.8v) output current (ma) efficiency (%) 40 50 60 70 80 90 100 0.1 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 4.2v load regulation (pwm mode; v out = 2.5v) output current (ma) v out error (%) -0.50 -0.25 0.00 0.25 0.50 0.1 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 5.0v v in = 4.2v output current (ma) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 4.2v v in = 5.0v efficiency vs. output current (pwm mode; v out = 2.5v)
aat1112 1.5a, 1.4mhz step-down converter 1112.2007.01.1.1 7 typical characteristics load regulation (pwm mode; v out = 1.2v) output current (ma) v out error (%) -0.50 -0.25 0.00 0.25 0.50 0.1 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 4.2v efficiency vs. output current (pwm mode; v out = 1.2v) output current (ma) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 4.2v load regulation (pfm mode; v out = 1.2v) output current (ma) v out error (%) -0.50 -0.25 0.00 0.25 0.50 0.1 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 4.2v efficiency vs. output current (pfm mode; v out = 1.2v) output current (ma) efficiency (%) 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 10000 v in = 2.7v v in = 3.6v v in = 4.2v supply current vs. supply voltage (v out = 1.8v; no load; pfm mode) supply voltage (v) supply current (a) 30 35 40 45 50 55 60 65 70 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 85c 25c -40c output voltage vs. temperature (v in = 3.6v; v out = 1.8v; i out = 1a) temperature ( c) output voltage change (%) -1.0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -40 -20 0 20 40 60 80
aat1112 1.5a, 1.4mhz step-down converter 8 1112.2007.01.1.1 typical characteristics n-channel r ds(on) vs. input voltage input voltage (v) r ds(on) (m ) 60 70 80 90 100 110 120 130 140 150 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 120c 85c 25c p-channel r ds(on) vs. input voltage input voltage (v) r ds(on) (m ) 90 100 110 120 130 140 150 160 170 180 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 120c 85c 25c enable soft start (v out = 3.6v; i out = 1.5a) time (100s/div) v out (1v/div) en (2v/div) i in (500ma/div) switching frequency vs. input voltage (i out = 1a) input voltage (v) switching frequency (mhz) 1.32 1.33 1.34 1.35 1.36 1.37 1.38 1.39 1.40 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 v out = 2.5v v out = 3.3v v out = 1.8v line regulation (v out = 1.8v; i out = 1a) supply voltage (v) output voltage error (%) -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 switching frequency vs. temperature (v in = 3.6v; v out = 1.8v; i out = 1a) temperature ( c) switching frequency (mhz) 1.24 1.26 1.28 1.30 1.32 1.34 1.36 1.38 1.40 -40 -20 0 20 40 60 80
aat1112 1.5a, 1.4mhz step-down converter 1112.2007.01.1.1 9 typical characteristics line transient response (v out = 1.8v; 1.5a load) time (200s/div) input voltage (top) (v) output voltage (bottom) (v) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 load transient response (v in = 3.6v; v out = 1.8v; no c ff ) time (20s/div) output voltage (top) (v) load current (bottom) (a) 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 load transient response (v in = 3.6v; v out = 1.8v; c ff = 100pf) time (20s/div) output voltage (top) (v) l oa d c urren t (bottom) (a) 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 light load switching waveform (pfm mode; v in = 3.6v; v out = 1.8v; 1ma load) time (100s/div) output voltage (ac coupled) (top) (mv) inductor ripple current (bottom) (ma) -24.0 -20.0 -16.0 -12.0 -8.0 -4.0 0.0 4.0 8.0 -100 0 100 200 300 400 500 600 700 light load switching waveform (pwm mode; v in = 3.6v; v out = 1.8v; 1ma load) time (2.5s/div) output voltage (ac coupled) (top) (mv) inductor ripple current (bottom) (ma) -12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 -400 -200 0 200 400 600 800 1000 1200 heavy load switching waveform (pwm mode; v in = 3.6v; v out = 1.8v; 1.5a load) time (2.5s/div) output voltage (ac coupled) (top) (mv) inductor ripple current (bottom) (ma) -12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
aat1112 1.5a, 1.4mhz step-down converter 10 1112.2007.01.1.1 functional block diagram functional description the aat1112 is a high performance 1.5a monolith- ic step-down converter operating at 1.4mhz switch- ing frequency. it minimizes external component size and optimizes efficiency over the complete load range. apart from the small bypass input capacitor, only a small l-c filter is required at the output. typically, a 3.3h inductor and a 22f ceramic capacitor are recommended for a 3.3v output (see table of recommended values). at dropout, the converter duty cycle increases to 100% and the output voltage tracks the input volt- age minus the r ds(on) drop of the p-channel high- side mosfet (plus the dc drop of the external inductor). the device integrates extremely low r ds(on) mosfets to achieve low dropout voltage during 100% duty cycle operation. this is advan- tageous in applications requiring high output volt- ages (typically > 2.5v) at low input voltages. the integrated low-loss mosfet switches can provide greater than 95% efficiency at full load. pfm operation maintains high efficiency under light load conditions (typically <150ma). the mode/ sync pin allows optional "pwm only" mode. this maintains constant frequency and low output ripple across all load conditions. alternatively, the ic can be synchronized to an external clock via the mode/ sync input. external synchronization is maintained between 0.6mhz and 3.0mhz. in battery-powered applications, as v in decreases, the converter dynamically adjusts the operating fre- quency prior to dropout to maintain the required duty cycle and provide accurate output regulation. en lx err. amp logic dh dl pgnd fb gnd input v ref vin vp mode/sync
aat1112 1.5a, 1.4mhz step-down converter 1112.2007.01.1.1 11 output regulation is maintained until the dropout voltage, or minimum input voltage, is reached. at 1.5a output load, dropout voltage headroom is approximately 200mv. the aat1112 typically achieves better than 0.5% output regulation across the input voltage and output load range. a current limit of 2.0a (typical) protects the ic and system components from short-circuit damage. typical no load quiescent current is 42a. thermal protection completely disables switching when the maximum junction temperature is detect- ed. the junction over-temperature threshold is 140c with 15c of hysteresis. once an over-tem- perature or over-current fault condition is removed, the output voltage automatically recovers. peak current mode control and optimized internal compensation provide high loop bandwidth and excellent response to input voltage and fast load transient events. soft start eliminates output volt- age overshoot when the enable or the input voltage is applied. under-voltage lockout prevents spuri- ous start-up events. control loop the aat1112 is a peak current mode step-down converter. the current through the p-channel mosfet (high side) is sensed for current loop control, as well as short-circuit and overload pro- tection. a fixed slope compensation signal is added to the sensed current to maintain stability for duty cycles greater than 50%. the peak current mode loop appears as a voltage-programmed current source in parallel with the output capacitor. the output of the voltage error amplifier programs the current mode loop for the necessary peak switch current to force a constant output voltage for all load and line conditions. internal loop compensation ter- minates the transconductance voltage error amplifi- er output. the reference voltage is internally set to program the converter output voltage greater than or equal to 0.6v. soft start/enable soft start limits the current surge seen at the input and eliminates output voltage overshoot. when pulled low, the enable input forces the aat1112 into a low-power, non-switching state. the total input current during shutdown is less than 1a. current limit and over-temperature protection for overload conditions, the peak input current is limited. to minimize power dissipation and stresses under current limit and short-circuit conditions, switching is terminated after entering current limit for a series of pulses. switching is terminated for seven consecutive clock cycles after a current limit has been sensed for a series of four consecutive clock cycles. thermal protection completely disables switching when internal dissipation becomes excessive. the junction over-temperature threshold is 140c with 15c of hysteresis. once an over-temperature or over-current fault conditions is removed, the output voltage automatically recovers. under-voltage lockout internal bias of all circuits is controlled via the vin input. under-voltage lockout (uvlo) guarantees sufficient v in bias and proper operation of all inter- nal circuitry prior to activation.
aat1112 1.5a, 1.4mhz step-down converter 12 1112.2007.01.1.1 component selection inductor selection the step-down converter uses peak current mode control with slope compensation to maintain stabil- ity for duty cycles greater than 50%. the output inductor value must be selected so the inductor current down slope meets the internal slope com- pensation requirements. the inductor should be set equal to the output voltage numeric value in h. this guarantees that there is sufficient internal slope compensation. manufacturer's specifications list both the inductor dc current rating, which is a thermal limitation, and the peak current rating, which is determined by the saturation characteristics. the inductor should not show any appreciable saturation under normal load conditions. some inductors may meet the peak and average current ratings yet result in excessive loss- es due to a high dcr. always consider the losses associated with the dcr and its effect on the total converter efficiency when selecting an inductor. the 3.3h cdrh4d28 series sumida inductor has a 49.2m worst case dcr and a 1.57a dc current rating. at full 1.5a load, the inductor dc loss is 97mw which gives less than 1.5% loss in efficien- cy for a 1.5a, 3.3v output. input capacitor select a 10f to 22f x7r or x5r ceramic capac- itor for the input. to estimate the required input capacitor size, determine the acceptable input rip- ple level (v pp ) and solve for c. the calculated value varies with input voltage and is a maximum when v in is double the output voltage. always examine the ceramic capacitor dc voltage coefficient characteristics when selecting the prop- er value. for example, the capacitance of a 10f, 6.3v, x5r ceramic capacitor with 5.0v dc applied is actually about 6f. figure 1: aat1112 schematic. c in(min) = 1 ?? - esr 4 f s ?? v pp i o ?? 1 - = for v in = 2 v o ?? v o v in v o v in 1 4 ?? 1 - ?? v o v in c in = v o v in ?? - esr f s ?? v pp i o pgnd 1 fb 6 vp 11 lx 12 en 8 n/c 4 pgnd 3 pgnd 2 vcc 7 sync 9 gnd 5 n/c 10 aat1112 tdfn33-12 u1 v in 3.3v 1 2 3 enable 10f c1 22 f c2 r2 59k r3 (optional) c3 3.3h l1 1 2 3 sync
aat1112 1.5a, 1.4mhz step-down converter 1112.2007.01.1.1 13 the maximum input capacitor rms current is: the input capacitor rms ripple current varies with the input and output voltage and will always be less than or equal to half of the total dc load current. for v in = 2 v o the term appears in both the input voltage ripple and input capacitor rms current equations and is a maximum when v o is twice v in . this is why the input voltage ripple and the input capacitor rms current ripple are a maximum at 50% duty cycle. the input capacitor provides a low impedance loop for the edges of pulsed current drawn by the aat1112. low esr/esl x7r and x5r ceramic capacitors are ideal for this function. to minimize stray inductance, the capacitor should be placed as closely as possible to the ic. this keeps the high frequency content of the input current localized, minimizing emi and input voltage ripple. the proper placement of the input capacitor (c1) can be seen in the evaluation board layout in the layout section of this datasheet (see figure 2). a laboratory test set-up typically consists of two long wires running from the bench power supply to the evaluation board input voltage pins. the induc- tance of these wires, along with the low-esr ceramic input capacitor, can create a high q net- work that may affect converter performance. this problem often becomes apparent in the form of excessive ringing in the output voltage during load transients. errors in the loop phase and gain meas- urements can also result. since the inductance of a short pcb trace feeding the input voltage is significantly lower than the power leads from the bench power supply, most applications do not exhibit this problem. in applications where the input power source lead inductance cannot be reduced to a level that does not affect the converter performance, a high esr tantalum or aluminum electrolytic should be placed in parallel with the low esr/esl bypass ceramic capacitor. this dampens the high q network and stabilizes the system. output capacitor the output capacitor limits the output ripple and provides holdup during large load transitions. a 10f to 22f x5r or x7r ceramic capacitor typi- cally provides sufficient bulk capacitance to stabi- lize the output during large load transitions and has the esr and esl characteristics necessary for low output ripple. the output voltage droop due to a load transient is dominated by the capacitance of the ceramic out- put capacitor. during a step increase in load cur- rent, the ceramic output capacitor alone supplies the load current until the loop responds. within two or three switching cycles, the loop responds and the inductor current increases to match the load current demand. the relationship of the output volt- age droop during the three switching cycles to the output capacitance can be estimated by: once the average inductor current increases to the dc load level, the output voltage recovers. the above equation establishes a limit on the minimum value for the output capacitor with respect to load transients. ?? 1 - = d (1 - d) = 0.5 2 = ?? v o v in v o v in 1 2 ?? i rms = i o 1 - ?? v o v in v o v in c out = 3 i load v droop f s ?? 1 - ?? v o v in v o v in i o rms(max) i 2 =
aat1112 1.5a, 1.4mhz step-down converter 14 1112.2007.01.1.1 the internal voltage loop compensation also limits the minimum output capacitor value to 10f. this is due to its effect on the loop crossover frequency (bandwidth), phase margin, and gain margin. increased output capacitance will reduce the crossover frequency with greater phase margin. adjustable output resistor selection the output voltage on the aat1112 is programmed with external resistors r1 and r2. to limit the bias current required for the external feedback resistor string while maintaining good noise immunity, the minimum suggested value for r2 is 59k . although a larger value will further reduce quies- cent current, it will also increase the impedance of the feedback node, making it more sensitive to external noise and interference. table 1 summa- rizes the resistor values for various output voltages with r2 set to either 59k for good noise immunity or 221k for reduced no load input current. table 1: aat1112 resistor values for various output voltages. thermal calculations there are three types of losses associated with the aat1112 step-down converter: switching loss- es, conduction losses, and quiescent current loss- es. conduction losses are associated with the r ds(on) characteristics of the power output switch- ing devices. switching losses are dominated by the gate charge of the power output switching devices. at full load, assuming continuous conduc- tion mode (ccm), a simplified form of the losses is given by: i q is the step-down converter quiescent current. the term t sw is used to estimate the full load step- down converter switching losses. for the condition where the step-down converter is in dropout at 100% duty cycle, the total device dis- sipation reduces to: since r ds(on) , quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input voltage range. given the total losses, the maximum junction tem- perature can be derived from the ja for the tdfn3-12 and tsopjw-12 packages, which is 50c/w and 160c/w respectively. r2 = 59k r2 = 221k v out (v) r1 (k ) r1 (k ) 0.8 19.6 75 0.9 29.4 113 1.0 39.2 150 1.1 49.9 187 1.2 59.0 221 1.3 68.1 261 1.4 78.7 301 1.5 88.7 332 1.8 118 442 1.85 124 464 2.0 137 523 2.5 187 715 3.0 237 887 3.3 267 1000 t j(max) = p total ja + t amb p total = i o 2 r ds(on)h + i q v in p total i o 2 (r ds(on)h v o + r ds(on)l [v in - v o ]) v in = + (t sw f s i o + i q ) v in
aat1112 1.5a, 1.4mhz step-down converter 1112.2007.01.1.1 15 figure 2: aat1112 evaluation board top side layout. figure 3: aat1112 evaluation board bottom side layout. layout the suggested pcb layout for the aat1112 is shown in figures 2 and 3. the following guidelines should be used to help ensure a proper layout. 1. the input capacitor (c1) should connect as close- ly as possible to vp and pgnd. 2. c2 and l1 should be connected as closely as possible. the connection of l1 to the lx pin should be as short as possible. 3. the feedback trace or fb pin should be sepa- rate from any power trace and connect as closely as possible to the load point. sensing along a high-current load trace will degrade dc load regulation. 4. the resistance of the trace from the load return to pgnd should be kept to a minimum. this will help to minimize any error in dc regulation due to differences in the potential of the inter- nal signal ground and the power ground. 5. connect unused signal pins to ground to avoid unwanted noise coupling. analogictech off gnd aat1112 enable gnd vout lx c2 gnd ll sync pwm l1 vin r2 c3 c1 r3 u1 on c4 analogictech off gnd aat1112 enable gnd vout lx c2 gnd ll sync pwm l1 vin r2 c3 c1 r3 u1 on analogictech off gnd aat1112 enable gnd vout lx c2 gnd ll sync pwm l1 vin r2 c3 c1 r3 u1 on
aat1112 1.5a, 1.4mhz step-down converter 16 1112.2007.01.1.1 design example specifications v o 3.3v @ 1.5a, pulsed load i load = 1.5a v in 2.7v to 4.2v (3.6v nominal) f s 1.2mhz t amb 85c in tdfn33-12 package output inductor l1 = v o (h) = 3.3h; see table 2. for sumida inductor cdrh4d28 3.3h dcr = 49.2m max. output capacitor v droop = 0.2v 1 23 1 3.3v (4.2v - 3.3v) 3.3h 1.2mhz 4.2v 23 rms(max) i l f s v in(max) = 3 i load v droop f s 3 1.5a 0.2v 1.2mhz c out = = = 18.8f; use 22f = 52marms (v out ) (v in(max) - v out ) = p esr = esr i rms 2 = 5m (52ma) 2 = 13.3w v o v o1 3.3 v 3.3v i 1 = ? 1 - = ? 1 - = 179ma l1 ? f s v in 3.3h ? 1.2mhz 4.2v i pk1 = i o1 + i 1 = 1.5a + 0.089a = 1.59a 2 p l1 = i o1 2 ? dcr = 1.5a 2 ? 49.2m = 110mw ? ? ? ? ? ? ? ?
aat1112 1.5a, 1.4mhz step-down converter 1112.2007.01.1.1 17 input capacitor input ripple v pp = 50mv aat1112 losses total losses can be estimated by calculating the dropout (v in = v o ) losses where the power mosfet r ds(on) will be at the maximum value. all values assume an 85c ambient temperature and a 120c junction temper- ature with the tdfn 50c/w package. the total losses are also investigated at the nominal lithium-ion battery voltage (3.6v). the simplified version of the r ds(on) losses assumes that the n-channel and p-channel r ds(on) are equal. t j(max) = t amb + ja p loss = 85 c + (50 c/w) 375mw = 104 c p total = i o 2 r ds(on) + (t sw f s i o + i q ) v in = 1.5a 2 152m + (5ns 1.2mhz 1.5a + 50 a) 3.6v = 375mw t j(max) = t amb + ja p loss = 85 c + (50 c/w) 360mw = 103 c p loss = i o1 2 r ds(on)h = 1.5a 2 0.16 = 0.36w i o rms(max) i p = esr i rms 2 = 5m (0.75a) 2 = 3mw 2 = = 0.75arms c in = = = 7.3f; use 10f 1 ?? - esr 4 f s ?? v pp i o1 + i o2 1 ?? - 5m 4 1.2mhz ?? 50mv 1.5a
aat1112 1.5a, 1.4mhz step-down converter 18 1112.2007.01.1.1 table 2: surface mount inductors. table 3: surface mount capacitors. manufacturer part number value voltage temp. co. case murata grm21br60j106ke19 10f 6.3v x5r 0805 murata grm21br60j226me39 22f 6.3v x5r 0805 inductance size rated i rms i sat dcr v out (v) (h) part number manufacturer (mm) current (a) (a) (a) ( ) 3.3 3.3 cdrh4d28 sumida 5x5x3 1.57 36.4 2.5 2.2 cdrh4d28 sumida 5x5x3 2.04 23.2 1.8 1.8 cdrh4d28 sumida 5x5x3 2.2 20.4 1.5 1.8 cdrh4d28 sumida 5x5x3 2.2 20.4 1.2 1.2 cdrh4d28 sumida 5x5x3 2.56 17.5 1.0 1.0 sd3114-1.0 cooper 3.1x3.1x1.45 1.67 2.07 0.042 0.8 1.0 sd3114-1.0 cooper 3.1x3.1x1.45 1.67 2.07 0.042 0.6 1.0 sd3114-1.0 cooper 3.1x3.1x1.45 1.67 2.07 0.042
aat1112 1.5a, 1.4mhz step-down converter 1112.2007.01.1.1 19 ordering information package information 3 tsopjw-12 all dimensions in millimeters. package marking 1 part number (tape and reel) 2 tsopjw-12 aat1112itp-0.6-t1 tdfn33-12 sbxyy aat1112iwp-0.6-t1 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 3. the leadless package family, which includes qfn, tqfn, dfn, tdfn and stdfn, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. a solder fillet at the exposed copper edge cannot be guaranteed and is not re quired to ensure a proper bottom solder connection. 0.20 + 0.10 - 0.05 0.055 0.045 0.45 0.15 7 nom 4 4 3.00 0.10 2.40 0.10 2.85 0.20 0.50 bsc 0.50 bsc 0.50 bsc 0.50 bsc 0.50 bsc 0.15 0.05 0.9625 0.0375 1.00 + 0.10 - 0.065 0.04 ref 0.010 2.75 0.25 all analogictech products are offered in pb-free packaging. the term ?pb-free? means semiconductor products that are in compliance with current rohs standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. for more information, please visit our website at http://www.analogictech.com/pbfree.
aat1112 1.5a, 1.4mhz step-down converter 20 1112.2007.01.1.1 tdfn33-12 all dimensions in millimeters. advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 ? advanced analogic technologies, inc. analogictech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an analogictech pr oduct. no circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. analogictech reserves the right to make changes to their products or specifi cations or to discontinue any product or service without notice. customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information b eing relied on is current and complete. all products are sold sub- ject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. analogictech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with anal ogictech?s standard warranty. testing and other quality con- trol techniques are utilized to the extent analogictech deems necessary to support this warranty. specific testing of all param eters of each device is not necessarily performed. analogictech and the analogictech logo are trademarks of advanced analogic technologies incorporated. all other brand and produ ct names appearing in this document are regis- tered trademarks or trademarks of their respective holders. top view bottom view detail "a" side view 3.00 0.05 index area detail "a" 1.70 0.05 3.00 0.05 0.05 0.05 0.23 0.05 0.75 0.05 2.40 0.05 pin 1 indicator (optional) 0.43 0.05 0.45 0.05 0.23 0.05 0.1 ref

▲Up To Search▲

Price & Availability of AAT1112ITP-06-T1

	To Download AAT1112ITP-06-T1 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .