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www.semtech.com 1 power management synchronous buck converter with programmable output sc190 the sc190 is a synchronous step-down converter with integrated power devices and an integrated front-end ldo to minimize input supply ripple. output voltage is programmable using two control bits, eliminating the need for feedback resistors tied to the output. the device is offered in four distinct variants with each variant providing four ?xed output voltage options to choose from. the front-end ldo can be bypassed externally to maximize ef?ciency. a second ldo is switched in place of the switching regulator for low current operation to further improve ef?ciency and reduce noise. the sc190s ?exible clocking scheme allows it to be synchronized to an external oscillator or controlled by the internal oscillator. the 1mhz switching frequency allows the use of small inductors and capacitors. the internal mosfet switches provide peak current greater than 500ma to achieve a dc output of at least 300ma. shutdown current is typically 0.1a. the sc190 has four different variants with four voltage settings each. it is designed for single-cell li-ion battery applications, but also performs well in ?xed 3.3v and 5v applications. ? less than 1mv supply ripple ? output voltage regulated by either the switching regulator or linear regulator ? dynamic handover between linear and switching regulator for maximum ef?ciency ? 2.7v to 5.5v input range ? 300ma guaranteed output current ? fixed frequency 1mhz operation or 750khz to 1.5mhz clocked operation ? no schottky diode required ? up to 95% ef?ciency (vin=bp) ? over-current protection ? over-voltage protection ? over-temperature protection ? soft start ? mlp-10, 3 x 3mm lead-frame, lead-free package ? low output noise < 100vrms ? cell phones ? cordless phones ? notebook and subnotebook computers ? pdas and mobile communicators ? wlan peripherals ? 1 li-ion or 3 nimh/nicd powered devices sc 190 4 . 7 f 4 . 7 f 4 . 7 h vin vout vin en sync / pwm vid 0 vid 1 mode lx vout bp gnd cin cbp cout lout 4 . 7 f description june 30, 2005 applications features typical application circuit features
2 ? 2005 semtech corp. www.semtech.com power management sc190 exceeding the speci?cations below may result in permanent damage to the device or device malfunction. operation outside of the parameters speci?ed in the electrical characteristics section is not implied. parameter symbol maximum units vin input v in -0.3 to 7 v logic inputs (sync/pwm, en, mode, vid0, and vid1) v n -0.3 to 7 v lx voltage v lx -1 to bp +1 v vout voltage v out -0.3 to vin + 0.3 v bp voltage v bp vin -0.3 to vin + 0.3 v thermal impedance junction to ambient ja *31 c/w vout short circuit to gnd t sc continuous s bp current i bp 0.8 a lx current i lx +1.2 a storage temperature t s -65 to +150 c junction temperature t jc +150 c peak ir re?ow temperature t lead 260 c * tied to pcb with 1 square inch, 2 ounce copper. unless otherwise noted: v in = 3.6v, sync/pwm = v in , mode = gnd, en = v in , t a = -40 to 85c. typical values are at t a = +25c. this device is esd sensitive. use of standard esd handling precautions is required. parameter symbol conditions min typ max units input voltage range v in v in = v bp 2.7 5.5 v v in v bp 2.9 5.5 v input voltage ripple v in pk-pk c in , c bp = 10f 1 mv l ine regulation v linereg 190a, b and d: see note (1) -0.3 0.3 %/v 190c: see note (2) -0.5 0.5 %/v load regulation v loadreg i out = 5ma to 300ma 0.002 %/ma p-channel on resistance r dsp i lx = 100ma 0.3 ? n-channel on resistance r dsn i lx = 100ma 0.2 ? start up time t start i out = 150ma 1.25 ms absolute maximum ratings electrical characteristics
3 ? 2005 semtech corp. www.semtech.com power management sc190 parameter symbol conditions min typ max units vout accuracy v out i out = 150ma -3 3 % mode = v in , i out = 1ma 3 3 % i out = 150ma, t a = +25c -1.5 1.5 % mode = v in , i out = 1ma, t a = +25c -1.5 1.5 % back-end ldo load regulation (beldo) vout loadreg i out = 100a to 5ma mode = v in -0.1 0.1 %/ma back-end ldo line regulation (beldo) vout l inereg v in = 2.7v to 5.5v mode = v in -0.3 0.3 %/v back-end ldo current limit (beldo) i out limldo mode = v in 20 40 60 ma front-end ldo (feldo) v bp i bp = 180ma (3) 300 325 mv p-channel current limit i lim(p) 500 630 860 ma n-channel current limit i lim(n -270 -420 -520 ma quiescent current i q mode = v in , i out = 100a (4) 10 15 a shutdown current i sd en = 0 0.1 1 a lx leakage current pmos i lxp v in = 5.5v, lx = 0v, en = 0 0.1 1 a lx leakage current nmos i lxn v in = 5.5v, lx = 5.5v, en = 0 -20 0.1 a output voltage noise e n c out = 4.7f, v out = 1v, i out = 1ma, 100hz < f < 100khz 93 v rms oscillator frequency f osc 0.87 1.0 1.12 mhz sync frequency (upper) f syncu 1.5 mhz sync frequency (lower) f syncl 750 khz unless otherwise noted: v in = 3.6v, sync/pwm = v in , mode = gnd, en = v in , t a = -40 to 85c. typical values are at t a = +25c. this device is esd sensitive. use of standard esd handling precautions is required. electrical characteristics (cont.)
4 ? 2005 semtech corp. www.semtech.com power management sc190 parameter symbol conditions min typ max units uvlo threshold (lower) v uvl 2.4 2.5 2.6 v uvlo hysteresis v uvlhys 50 mv thermal shutdown t hi 145 c thermal shutdown hysteresis t hysr 10 c logic input high vih en, sync/pwm, mode, vid0, vid1 1.6 v logic input low vil en, sync/pwm, mode, vid0, vid1 0.6 v logic input current high i ih en, sync/pwm, mode, vid0, vid1 -2 0.1 2 a logic input current low i il en, sync/pwm, mode, vid0, vid1 -2 0.1 2 a unless otherwise noted: v in = 3.6v, sync/pwm = v in , mode = gnd, en = v in , t a = -40 to 85c. typical values are at t a = +25c. this device is esd sensitive. use of standard esd handling precautions is required. notes: (1) line regulation is tested with 2.7v < vin < 5.5v and the following output voltage settings: sc190a - 1.8v sc190b - 1.8v sc190d - 1.4v (2) line regulation is tested with 3.7v < vin < 5.5v and vout = 2.6v for the sc190c version. the input voltage range is reduced due to the higher output voltage settings of the sc190c. this also forces the speci?cation range to grow wider because it is expressed as a percentage of the input voltage range. (3) tested at i bp = 180ma. equivalent to i out = 300ma at v out = 1.8v. (4) i q = i in - i out. electrical characteristics (cont.)
5 ? 2005 semtech corp. www.semtech.com power management sc190 pin con?guration ordering information top view 1 2 3 4 10 9 8 7 5 6 mlp 10 : 3 x 3 10 lead bp vin vout en mode lx gnd vid 1 vid 0 sync / pwm t device package sc190aimltrt (1) mlp 3x3-10 sc190bimltrt (1) sc190cimltrt (1) sc190dimltrt (1) sc190aevb evaluation board (2) SC190BEVB sc190cevb sc190devb (1) lead-free packaging only. this product is fully weee and rohs compliant. available on tape and reel only. a reel contains 3000 devices. (2) part speci?c evaluation boards - consult factory for availability. programmable output voltage vid1 vid0 sc190a sc190b sc190c sc190d 0 0 1.8v 1.2v 2.5v 1.3v 0 1 1.85v 1.5v 2.8v 1.35v 1 0 1.75v 1.0v 2.6v 1.375v 1 1 1.9v 1.8v 2.7v 1.4v pin # pin name pin function 1 bp regulated output, with respect to vin, of the front-end ldo. a decoupling capacitor is connected to this pin. this input goes directly to the internal mosfet switch. 2 vin input power supply voltage . 3 vout regulated output voltage and feedback for sc190. 4 en enable (digital input): high input enables the sc190, a low disables and reduces quiescent current to 0.1a. in shutdown, lx becomes high impedance. 5 mode mode select pin (digital input): mode = vin - linear regulator mode; mode = gnd - switcher mode. 6 sync/pwm oscillator synchronization input. tie to vin for forced continuous mode or external clock for frequency synchronization. 7 vid0 logic level bit 0 used in conjunction with vid1 to set the output voltage. 8 vid1 logic level bit 1 used in conjunction with vid0 to set the output voltage. 9 gnd ground. 10 lx inductor connection to the switching fets. t thermal pad for heatsinking purposes. not connected internally. connects to ground plane using multiple vias. pin descriptions
6 ? 2005 semtech corp. www.semtech.com power management sc190 block diagram vin bp gnd voltage select en vid 1 vid 0 vout control logic ldo error amp front - end ldo current amp lx p limit amp ref ldo error amp 500 mv reference handover timing mode sync / pwm back - end ldo ref n limit comp ref osc and slope generator pwm comp error amp 2 1 10 9 4 8 7 3 5 6
7 ? 2005 semtech corp. www.semtech.com power management sc190 applications information sc190 detailed description the sc190 is a step-down, pulse-width-modulated (pwm) dc-dc converter with a low dropout (ldo) pre-regulator and a low current ldo regulator for operation in low power modes. the device has an internal synchronous recti?er and does not require a schottky diode on the lx pin. the device is designed to operate as a buck converter in pwm mode with a ?xed frequency of 1mhz, but at loads below 5ma, the part can be operated as an ultra-low current ldo regulator to minimize supply current. programmable output voltage the sc190 has four device variants (sc190a, sc190b, sc190c, sc190d) each with a distinct range of output voltages. the output voltage of each variant has four predetermined values which can be individually selected by the correct programming of the vid0 and vid1 pins. (see programmable output voltage table on page 5). note that the sc190c has much higher output voltage settings than the other three variants. this device was intended for use with higher input voltages, so some performance over the entire input voltage range cannot be guaranteed. switcher mode with less than 1mv supply ripple this is a ?xed frequency current mode architecture with the input supply for the switching regulator pre-regulated by a front-end ldo regulator. this technique reduces the supply voltage ripple from 20mv, typically seen from a switching converter, to approximately 1mv for the sc190. the supply to the switcher is regulated to the supply voltage minus approximately 300mv. current feedback for the switching regulator is through the pmos current path and it is ampli?ed and summed with the internal slope compensation network and level shift. the voltage feedback loop is through an internal feedback divider. the on time is determined by compar- ing the summed current feedback and the output of the error ampli?er. the period is set by the onboard oscillator or by an external clock attached to the sync/pwm pin. ef?ciency at moderate to high loads can be improved by shorting the vin to bp pins at the expense of higher input voltage ripple. continuous conduction & oscillator synchronization the sc190 is designed to operate in continuous conduction mode thereby maintaining a ?xed frequency. when the sync/pwm pin is tied high the part runs under control of the internal oscillator. the part can be synchronized to an external clock by driving a clock signal into the sync/ pwm pin. the part synchronizes to the rising edge of the clock. back end ldo mode the sc190 ultra-low current linear regulator regulates the same output as the switching regulator. the linear regulator minimizes the supply current drawn at light loads consuming only 10a when supporting a 100a load. the sc190 can swap between switching regulator and linear regulator mode under control of the mode pin (see handover section). in this way the part either operates at a ?xed frequency or dc output, thereby never generating load dependant frequencies that are typically seen with lightly loaded switching regulators. handover (switcher mode to ldo regulator mode, ldo regulator mode to switcher mode) the device can be switched between switcher mode and linear regulator mode and back to switcher mode without having to disable and re-enable the part. the output maintains regulation during the switch over. wait time v mode (pin 5) 200 s < 5ma i out (pin 3) < 300ma time linear regulator mode to switching mode transition wait time v mode (pin 5) 100 s < 5ma < 300ma time switching mode to linear regulator mode transition linear regulator i out specification applies i out (pin 3) switching converter i out specification applies s s
8 ? 2005 semtech corp. www.semtech.com power management sc190 applications information the output load in switcher mode has to be reduced to a load that the ldo regulator can support before switching between the two modes to minimize output voltage deviation. the transition from ldo regulator mode to switcher mode requires the load to be kept at levels the ldo regulator can support for a given time period after the mode pin has been pulled low (see timing diagram on page 7). protection features the sc190 provides the following protection features: ? thermal shutdown ? current limit ? overvoltage protection ? soft-start thermal shutdown the device has a thermal shutdown feature to protect the device if the junction temperature exceeds 150c. in thermal shutdown the pwm drive is disabled tri-stating the lx output and the front-end ldo is disabled. the device will not be enabled again until the temperature reduces by 10c. if during this time the output falls by greater than 60% of its regulation voltage a soft start will be invoked. thermal shutdown is not active during ldo mode in order to minimize supply current. current limit the part has a number of current limit functions. the front- end ldo regulator has a current limit set at approximately 500ma, which will protect the feldo regulator in the event of a pulsed short circuit. the pmos and nmos power devices of the buck switcher stage are protected by current limit functions. in the case of a short to ground on the output, the part enters frequency foldback mode which causes the switching frequency to divide by a factor determined by the output voltage, stopping the inductor current stair stepping. the back-end ldo regulator has a current limit feature which will limit the maximum output current during ldo regulator mode to 50ma. overvoltage protection overvoltage protection is provided on the sc190. in the event of an overvoltage on the output in switcher mode, the drive to the pwm stage is disabled and the part will not resume switching until the output voltage has fallen to below 2% of the regulation voltage. soft-start the soft-start mode is enabled after every shutdown cycle to limit in-rush current. in conjunction with the frequency foldback this controls the maximum current during the start-up. the switchers pmos current limit is stepped from 25%, to 50%, to 75%, and then 100% of its typical value by the internal oscillator. the oscillator frequency is stepped by 1 / 8 , 1 / 4 , 1 / 2 and 1 under the control of 4 output voltage thresholds causing modulation of the soft- start timer (see current limit description in the protection features section). as soon as the part reaches regulation, soft-start mode is disabled. 100 percent duty cycle operation the sc190c has a 100% duty cycle mode of operation to allow the switcher to regulate the output at low input voltage to high output voltage conditions. as the input supply drops towards the output voltage, the pmos on- time increases linearly until a point where the pmos fet is on for 100% of the time. once the pmos is on dc the output voltage will track the input voltage minus the voltage drop across the pmos power device according to the following relationship: v out = v in C i out ( r dsp + r ind ) v out = output voltage v in = input voltage i out = output current r dsp = pmos switch on resistance r ind = series resistance of the inductor
9 ? 2005 semtech corp. www.semtech.com power management sc190 applications information (cont.) output filter the sc190 series of synchronous step-down converters have internal loop compensation. the internal compensation is designed to work with a certain output ?lter corner frequency de?ned by the equation: the internal compensation is optimized to operate with an output ?lter, l=4.7h & cout = 10f. when selecting output ?lter components the lc product should not vary over a wide range. table 1: output filter combinations l(h) c out (f) 4.7 4.7 4.7 10 10 10 inductor selection as previously stated the value of the inductor should be in the range 4.7h to 10h. the magnitude of the inductor current ripple is dependant on the inductor value and can be determined by the following equation: this equation demonstrates the relationship between v in ,v out & i l . the inductor ripple current decreases with higher inductance & increases with higher v in or v out . to maximize ef?ciency the inductor should have a low dcr to minimize the conduction losses. as a minimum requirement the dc current rating of the inductor should be equal to the maximum load current plus half of the inductor current ripple and can be determined by the following equation: the selection of smaller inductor & capacitor values will move the corner frequency, having an impact on system stability. due to this issue the practical lower limit for the inductor value is 4.7h. alternatively, set the inductor saturation current to be greater than the switch current limit as a maximum limit. i sat > pmos. final inductor selection will depend on various design considerations such as ef?ciency, emi, size and cost. table 2 lists the manufacturers of practical inductor options. table 2 - recommended inductors manufacturer part number value (h) dcr (?) rated current (a) saturation current (a) tolerance % dimensions (lxwxh mm) tdk ldr655312t-4r7w 4.7 0.206 0.9 - 20 6.5 x 5.3 x 1.2 sumida cdrh3d16ld 4.7 0.073 0.68 - 30 4 x 4 x 1.8 taiyo yuden lmnp04sb100m 10 0.066 0.9 - 20 5 x 5 x 2 coilcraft lps3015 10 0.044 - 0.65 20 3 x 3 x 1.5 coilcraft lp06610-103m 10 0.41 - 0.8 20 6.9 x 3.8 x 1.0 c l 2 1 f c ? = f l vi vo 1 vo il ? ? ? ? ? ? ? ? = ? 2 il (max) iout ilpk ? + =
10 ? 2005 semtech corp. www.semtech.com power management sc190 applications information (cont.) pcb layout considerations poor layout can degrade the performance of the dc- dc converter and can be a contributory factor in emi problems, ground bounce and resistive voltage losses. poor regulation and instability can result. a few simple design rules can be implemented to ensure good layout: 1. place the inductor and ?lter capacitors as close to the device as possible and use short wide traces between the power components. 2. route the output voltage feedback path away from inductor and lx node to minimize noise and magnetic interference. use a ground plane to further reduce noise interference on sensitive circuit nodes. suggested layout
11 ? 2005 semtech corp. www.semtech.com power management sc190 cin selection the source input current to the sc190 buck converter is a dc supply current with a triangular ripple riding on it. to prevent large input voltage ripple a low esr ceramic capacitor is required. a minimum value of 4.7f should be used for suf?cient input voltage ?ltering and a 10f mlcc should be used for optimum input voltage ?ltering. input voltage ripple of approximately 1mv can be achieved when c in = 10f, and the front-end ldo regulator is active and pre-regulating the input supply to the switching regulator. (see page 12: input voltage ripple graphs). cout selection a 10f ceramic capacitor is recommended for the output ?lter capacitor. output voltage ripple is dominated by the ?lter capacitance as shown in the following equation: choose an x7r or x5r ceramic dielectric for low esr and superior temperature and voltage characteristics. do not use y5v capacitors - their temperature coef?cients make them impractical for this application. table 3: recommended capacitors manufacturer part number value (f) rated voltage (vdc) type case size murata grm188r60j475ke19d 4.7 6.3 x5r 0603 murata grm188r60g106me47d 10 4 x5r 0603 tdk c1608x5rog106m 10 4 x5r 0603 applications information (cont.) ) esr ( cout ) ripple ( il ripple _ vout ? ? =
12 ? 2005 semtech corp. www.semtech.com power management sc190 input voltage ripple (feldo bypassed) v in (ac) lx i l note: conditions: l = 10h, cout = 10f handover transition linear to switcher mode lx v out (ac) i l input voltage ripple (feldo active) v in (ac) lx i l handover transition switcher to linear mode lx v out (ac) i l typical characteristics
13 ? 2005 semtech corp. www.semtech.com power management sc190 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 output current (a) efficiency (%) vin = 3.0v vin = 3.6v vin = 4.2v 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 output current (a) efficiency (%) vin = 3.0v vin = 3.6v vin = 4.2v -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.7 0.9 1.1 1.3 1.5 frequency (mhz) %vout (nom) (v) v in = 3.6v v out = 1.0v i out = 0.15a 10 o 10 o a o v out = 1.v o a v out = 1.v i v v out = 1.0v o v typical characteristics (cont.) 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 input voltage (v) output voltage (v) v out = 2.8v i out = 0.15a v out = 2.5v i out = 0.15a 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 frequency (mhz) input voltage (v) 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 input voltage (v) output voltage (v) v out 2.8v i out 0.15a v out 2.5v i out 0.15a
14 ? 2005 semtech corp. www.semtech.com power management sc190 0 2 4 6 8 10 12 14 -40 -20 0 20 40 60 80 100 120 temperature (c) quiescent current (a) vin = 2.7v vin = 3.6v vin = 5.5v 0 200 400 600 800 1000 1200 -40 -20 0 20 40 60 80 100 120 temperature (c) oscillator frequency (khz) vin = 2.7v vin = 3.6v vin = 5.5v quiescent current vs temperature oscillator frequency vs temperature input current vs output current typical characteristics (cont.) 0.01 0.1 1 10 100 1000 0.01 0.1 1 10 100 1000 output current (ma) input current (ma) linear regulator switching regulator
15 ? 2005 semtech corp. www.semtech.com power management sc190 5 6 7 4 3 1 8 2 1 2 3 4 on dip_sw 1 tp12 vo ut sense tp1 1 gnd load tp1 3 gnd v in 1 2 j1 jumper1 tp1 tp9 tp8 tp 7 tp1 0 tp2 en sync/pwm vid0 mode vid1 c3 10uf vout vin c1 10uf gnd gnd vin vout lx node r2 1m r3 1m r4 1m r5 1m c2 10uf 1 2 l1 10uh r1 1m tp3 tp4 tp5 tp6 en 4 sync/pwm 6 vid0 7 gnd 9 bp 1 vo ut 3 vid1 8 lx 1 0 mode 5 vin 2 pa d 1 1 sc190 u1 evaluation board schematic
16 ? 2005 semtech corp. www.semtech.com power management sc190 top copper bottom copper top silkscreen bottom silkscreen evaluation board gerber plots
17 ? 2005 semtech corp. www.semtech.com power management sc190 190 n yyww xxxx yy = two digit year of manufacture ww = two digit week of manufacture xxxx = lot number " n" can be a , b , c , or d min aaa bbb b e l n d c e a1 a2 a dim millimeters nom dimensions max nom inches min max .114 .118 .122 2.90 3.00 3.10 - - - - (laser mark) indicator pin 1 1 n 2 notes: controlling dimensions are in millimeters (angles in degrees). coplanarity applies to the exposed pad as well as terminals. 2. 1. .003 .007 .042 10 .009 .048 - .000 .031 (.008) 0.08 0.23 10 .011 .052 0.18 1.06 .039 - .002 - 0.00 0.80 1.31 0.30 1.21 - 0.05 1.00 (0.20) .004 0.10 0.50 bsc .020 bsc 0.30 .012 .020 .016 0.40 0.50 a aaa c a2 seating plane a1 a bxn bbb c a b b e c c d lxn e e .074 .079 .083 1.87 2.02 2.12 outline drawing - mlp-10 3x3 marking information
18 ? 2005 semtech corp. www.semtech.com power management sc190 semtech corporation power management products division 200 flynn road, camarillo, ca 93012 phone: (805) 498-2111 fax (805)498-3804 contact information .087 .055 2.20 1.40 .150 .020 .012 .037 3.80 0.30 0.95 0.50 (.112) .075 1.90 (2.85) k h x this land pattern is for reference purposes only. consult your manufacturing group to ensure your company's manufacturing guidelines are met. notes: 1. inches dimensions g k h x y p z c dim millimeters y z g (c) p land pattern - mlp-10 3x3

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