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1 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 general description the aat2786 is a dual output power solution. it includes a 1.5a, 1.4mhz, high-efficiency step-down converter and a high performance 150ma ldo regulator. the step- down regulator output voltage is adjustable from 0.6v to v in . the ldo regulator has a factory preset fixed output voltage from 1.2v to 3.3v. the step-down converter consumes only 42 a of no-load quiescent current and is designed to maintain high effi- ciency throughout the load range. the step-down con- verter has ultra-low r ds(on) integrated mosfets and can operate up to 100% duty cycle to enable high output voltage, high current applications which require a low dropout threshold. the aat2786 provides excellent tran- sient response and high output accuracy across the operating range. pulling the mode/sync pin high enables ?pwm only? mode, maintaining constant fre- quency and low output ripple across the operating range. alternatively, the converter may be synchronized to an external clock input via the mode/sync pin. the micropower low dropout linear regulator in the aat2786 has been specifically designed for high-speed turn-on and turn-off performance, fast transient response, and good noise and power supply ripple rejection (psrr), making it ideal for powering sensitive circuits with fast switching requirements. over-temperature and short-circuit protection safeguard the aat2786 and system components from damage. features ?? v in range : 2.5v to 5.5v ?? 1.5a step-down converter ? v out range: 0.6v to v in ? 95% peak efficiency ? high efficiency across load range ? 42 a no load quiescent current ? optional ?pwm only? low noise mode ? current limit and soft start ?? 150ma ldo regulator ? v out range: 1.2v to 3.3v (fixed) ? high power supply rejection ratio ? low output noise ?? independent enable pins ?? integrated power mosfets ?? over-temperature protection ?? tdfn34-16 package ? -40c to +85c temperature range applications ?? cellular and smart phones ?? pdas, palmtops ?? digital still and video cameras ?? portable instruments ?? battery-powered applications typical application r2 adj r3 59k c8 10nf c6 1f 3.3h l1 c1 opt c7 2.2f buck out ldo out ldo in buck in c5 opt c4 22f c3 1f r1 100 c2 10f vin 12 mode/sync 14 vp 16 vp 15 ldoin 11 buck_en 13 ldo_en 9 n/c 10 ldo_out 6 byp 8 lx 2 lx 1 gnd 4 pgnd 3 ldo_gnd 7 fb 5 aat2786irn u1 on/off on/off on/off
2 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 pin descriptions pin # symbol description 1, 2 lx step-down converter 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. 3 pgnd step-down converter main power ground return pin. connect to the output and input capacitor return. 4 gnd non-power signal ground pin. 5fb step-down converter feedback input pin. this pin is connected either directly to the converter output or to an external resistive divider for an adjustable output. 6 ldoout ldo output pin; should be decoupled with 2.2 f ceramic capacitor. 7 ldo_gnd ldo ground connection pin. 8 byp ldo bypass capacitor connection; to improve ac ripple rejection, connect a 10nf capacitor to gnd. this will also provide a soft start function. 9 ldo_en ldo enable pin; this pin should not be left oating. when pulled low, the ldo pmos pass transistor turns off and all internal circuitry enters low-power mode, consuming less than 1 a. 10 n/c open 11 ldoin ldo input voltage pin; should be decoupled with 1 f or greater capacitor. 12 vin step-down converter power supply. supplies power for the internal circuitry. 13 buck_en step-down converter enable pin. a logic low disables the step-down converter and it consumes less than 1 a of current. when connected high, it resumes normal operation. 14 mode/sync connect to ground for light-load/pwm mode and optimized ef ciency throughout the load range. con- nect high for low noise pwm operation under all operating conditions. connect to an external clock for synchronization (pwm only). 15,16 vp step-down converter input voltage for the power switches. pin configuration tdfn34-16 (top view) pgnd gnd fb lx lx 3 ldoout ldo_gnd byp mode/sync buck_en vin vp vp ldoin n/c ldo_en 4 5 1 2 6 7 8 14 13 12 16 15 11 10 9
3 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 absolute maximum ratings t a = 25c unless otherwise noted. 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 fb fb pin to gnd -0.3 to v in + 0.3 v n mode/sync, buck_en to gnd -0.3 to 6.0 v ldoin vldoin to ldo_gnd 6.0 v enin(max) ldo_en to ldo_gnd -0.3 to v in + 0.3 t j maximum junction operating temperature -40 to +150 c t lead maximum soldering temperature (at leads, 10 sec) 300 thermal information symbol description value units p d maximum power dissipation 1 2.0 w ? ja thermal resistance 50 c/w v ldoin ldo input voltage (v ldout + v do ) to 5.5 v 1. derate 20mw/oc above 25c ambient temperature. stresses above those listed in absolute maximum ratings may cause permanent d amage to the device. functional opera- tion at conditions other than the operating conditions specified is not implied. 2. mounted on an fr4 board. 3. to calculate minimum input voltage, use the following equation: v in(min) = v out(max) + v do(max) as long as v in 2.5v.
4 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 electrical characteristics 1 v in =3.6v; t a = -40 o c to 85 o c unless otherwise noted. typical values are at t a = 25 o c. symbol description conditions min typ max units step-down converter v in input voltage 2.5 5.5 v v out output voltage range 0.6 v in v v uvlo uvlo threshold v in rising 2.5 v hysteresis 150 mv v in falling 1.7 v v out output voltage tolerance i out = 0a to 1.5a, v in = 2.4v to 5.5v -3.0 3.0 % 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 vin 1.0 a 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 accuracy (adjustable version) no load, t a = 25c 0.591 0.60 0.609 v i fb fb leakage current v out = 1.0v 0.2 a f osc internal oscillator frequency t a = 25c 1.12 1.4 1.68 mhz synchronous clock 0.60 3.0 t s start-up time from enable to output regulation 150 s t sd over-temperature shutdown threshold 140 c t hys over-temperature shutdown hysteresis 15 c 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 a 1. the aat2786 is guaranteed to meet performance specifications over the -40c to +85c operating temperature range and is assu red by design, characterization, and correla- tion with statistical process controls.
5 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 electrical characteristics (continued) v ldoin = v out(nom) + 1v for v out options greater than 1.5v. v in = 2.5 for v out 1.5v. i out = 1ma, c out = 2.2 f, c in = 1 f, t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c. symbol description conditions min typ max units ldo regulator v ldoout output voltage tolerance i ldoout = 1ma to 150ma t a = 25c -1.5 1.5 % t a = -40c to 85c -2.5 2.5 i ldoout output current v ldoout > 1.2v 150 ma v do dropout voltage 2, 3 i ldoout = 150ma 200 300 mv i sc short-circuit current v ldoout < 0.4v 600 ma i q ground current v in = 5v, no load, en = v in 70 125 a i sd shutdown current v in = 5v, en = 0v 1 a v out / v out * v in line regulation v in = v out + 1 to 5.0v 0.09 %/v v out(line) dynamic line regulation v in = v ldoout + 1v to v ldoout + 2v, i ldoout = 150ma, t r /t f = 2 s 2.5 mv v out(load) dynamic load regulation i ldoout = 1ma to 150ma, t r < 5 s 30 mv psrr power supply rejection ratio i ldoout = 10ma, c byp = 10nf 1 khz 67 db 10khz 47 1mhz 45 e n output noise noise power bw = 300hz - 50khz 50 vrms t sd over-temperature shutdown threshold 145 c t hys over-temperature shutdown hysteresis 12 c t c output voltage temperature coef cient 22 ppm/c enable v il enable threshold low 0.6 v v ih enable threshold high 1.4 v i en_buck enable leakage current v en_buck = 5v 1 a i en_ldo enable leakage current v en_ldo = 5v 1.0 a t endly enable delay time byp = open 15 s 1. v do is defined as v ldoin - v ldoout when v ldoout is 98% of nominal. 2. for v ldoout < 2.3v, v do = 2.5v - v ldoout .
6 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical characteristics?step-down converter efficiency vs. output current (light-load 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 load regulation (light-load 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 (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 (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 (light-load 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 (light-load 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
7 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical characteristics?step-down converter 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) 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) efficiency vs. output current (light-load 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 (light-load 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 (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 (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
8 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical characteristics?step-down converter efficiency vs. output current (light-load 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 load regulation (light-load 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 (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 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 supply current vs. supply voltage (v out = 1.8v; no load; light-load 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
9 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical characteristics?step-down converter 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 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. 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 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) 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 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
10 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical characteristics?step-down converter 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 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 light load switching waveform (light-load 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 load transient response (v in = 3.6v; v out = 1.8v; c ff = 100pf) time (50s/div) output voltage (top) (v) load current (bottom) (a) -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 load transient response (v in = 3.6v; v out = 1.8v; no c ff ) time (50s/div) output voltage (top) (v) load current (bottom) (a) -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 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
11 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical characteristics?ldo dropout voltage vs. temperature 0 20 40 60 80 100 120 140 160 180 200 220 240 260 -40-30-20-100 102030405060708090100110120 temperature ( i l = 150ma i l = 100ma i l = 50ma dropout characteristics 2.00 2.20 2.40 2.60 2.80 3.00 3.20 2.70 2.80 2.90 3.00 3.10 3.20 input voltage (v) output voltage (v) i out = 150ma i out = 100ma i out = 50ma i out = 10ma i out = 0ma dropout voltage vs. output current 0 50 100 150 200 250 300 0 25 50 75 100 125 150 output current (ma) dropout voltage (mv) 85 c 25 c -40 c ground current vs. input voltage 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 2 2.5 3 3.5 4 4.5 input voltage (v) ground current ( i out = 0ma i out = 10ma i out = 50ma i out = 150ma quiescent current vs. temperature 0 10 20 30 40 50 60 70 80 90 100 -40-30-20-10 0 10203040506070 8090100110120 temperature ( output voltage vs. temperature 1.196 1.197 1.198 1.199 1.200 1.201 1.202 1.203 -40-30-20-10 0 1020 30 40 5060 7080 90100 temperature (
12 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical characteristics?ldo initial power-up response time (c byp = 10nf) time (400s/div) v en (5v/div) v out (1v/div) time (50s/div) v en (5v/div) v out (1v/div) turn-off response time (c byp = 10nf) turn-on time from enable (v in present) (c byp = 10nf) time (5s/div) v en (5v/div) v out (1v/div) over-current protection -200 0 200 400 600 800 1000 1200 time (20ms/div) output current (ma) line transient response 2.98 2.99 3.00 3.01 3.02 3.03 3.04 time (100s/div) input voltage (v) 0 1 2 3 4 5 6 output voltage (v) v out v in load transient response 2.60 2.65 2.70 2.75 2.80 2.85 2.90 time (100s/div) output voltage (v) -100 0 100 200 300 400 500 output current (ma) v out i out
13 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical characteristics?ldo aat2786 self noise (c out = 10f, ceramic) 0.001 0.01 0.1 1 10 0.01 0.1 1 10 100 1000 10000 frequency (khz) noise amplitude (v/rthz) band power: 300hz to 50khz = 44.6vrms/rthz 100hz to 100khz = 56.3vrms/rthz v ih and v il vs. v in 1.050 1.075 1.100 1.125 1.150 1.175 1.200 1.225 1.250 2.5 3.0 3.5 4.0 4.5 5.0 5.5 input voltage (v) v ih v il
14 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 functional description the aat2786 is a dual output power solution. it includes a 1.5a, 1.4mhz, high-efficiency step-down converter and a high performance 150ma ldo regulator. the step- down regulator output voltage is adjustable from 0.6v to v in . the ldo regulator has a factory preset fixed output voltage from 1.2v to 3.3v. the on and off states of the step-down converter and the ldo regulator are indepen- dently controlled by separate enable pins. step-down converter the step-down converter in the aat2786 is a high perfor- mance 1.5a monolithic step-down converter operating at 1.4mhz switching frequency. it minimizes external compo- nent 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 3.3 h inductor and a 22 f ceramic capacitor are recommended for a 3.3v output (see table of recommended values). functional block diagram bias oscillator control circuit rldofb1 rldofb2 vp lx ldo_gnd ldoout vin ldoin mode/sync fb pgnd buck_en ldo_en gnd byp
15 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 at dropout, the step-down converter duty cycle increases to 100% and the output voltage tracks the input voltage 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 advantageous 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. light-load operation maintains high efficiency under light load con- ditions (typically <150ma). the mode/sync pin allows optional ?pwm only? mode. this maintains constant fre- quency and low output ripple across all load conditions. alternatively, the ic can be synchronized to an external clock via the mode/ sync input. external synchroniza- tion is maintained between 0.6mhz and 3.0mhz. in battery-powered applications, as v in decreases, the converter dynamically adjusts the operating frequency prior to dropout to maintain the required duty cycle and provide accurate output regulation. 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 step-down converter in the aat2786 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 cur- rent is 42 a. thermal protection completely disables switching when the maximum junction temperature is detected. the junction over-temperature threshold is 140c with 15c of hysteresis. once an over-temperature or over-current fault condition is removed, the output voltage automati- cally recovers. peak current mode control and optimized internal com- pensation provide high loop bandwidth and excellent response to input voltage and fast load transient events. soft start eliminates output voltage overshoot when the step-down converter is enabled. under-voltage lockout prevents spurious start-up events. control loop the step-down converter in the aat2786 is a peak cur- rent 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 protection. 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 terminates the transconductance voltage error amplifier output. the reference voltage is internally set to program the con- verter output voltage greater than or equal to 0.6v. soft start/enable soft start limits the current surge seen at vin and elim- inates output voltage overshoot. when en_buck input is pulled low the step-down converter is forced into a low- power, non-switching state. the total input current dur- ing shutdown is less than 1 a. current limit and over-temperature protection for overload conditions, the peak input current in the step-down converter is limited. to minimize power dis- sipation and stresses under current limit and short-cir- cuit conditions, switching is terminated after entering current limit for a series of pulses. switching is termi- nated 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) in the step-down con- verter guarantees sufficient vin bias and proper opera- tion of all internal circuitry prior to activation.
16 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 ldo functional description the ldo regulator in the aat2786 is intended for applica- tions with output current load requirements from no load to 150ma. the advanced circuit design of the aat2786 ldo regulator has been specifically optimized for very fast start-up and shutdown timing. this proprietary cmos ldo has also been tailored for superior transient response characteristics. these traits are particularly important for applications that require fast power supply timing, such as gsm cellular telephone handsets. the high-speed turn-on capability of the ldo regulator is enabled through the implementation of a fast start control circuit, which accelerates the turn-on behavior of fundamental control and feedback circuits. fast turn-off response time is achieved by an active output pull-down circuit, which is enabled when the ldo regulator is placed in shutdown mode. this active fast shutdown cir- cuit has no adverse effect on normal device operation. the aat2786 ldo regulator has very fast transient response characteristics, which is an important feature for applications in which fast line and load transient response are required. this rapid transient response behavior is accomplished through the implementation of an active error amplifier feedback control. this proprietary circuit design is unique to this micropower ldo regulator. the ldo regulator output has been specifically optimized to function with low-cost, low-esr ceramic capacitors. however, the design will allow for operation over a wide range of capacitor types. a bypass pin has been provided to allow the addition of an optional voltage reference bypass capacitor to reduce output self noise and increase power supply ripple rejec- tion. device self noise and psrr will be improved by the addition of a small ceramic capacitor to this pin. however, increased cbypass values may slow down the ldo regulator turn-on time. enable function the aat2786 features an ldo regulator enable/ disable function. this pin (en) is active high and is compatible with cmos logic. to assure the ldo regulator will switch on, the en turn-on control level must be greater than 1.5v. the ldo regulator will go into the disable shut- down mode when the voltage on the en pin falls below 0.6v. if the enable function is not needed in a specific application, it may be tied to v in to keep the ldo regula- tor in a continuously on state. when the ldo regulator is in shutdown mode, an inter- nal 1.5k resistor is connected between vout and gnd. this is intended to discharge c out when the ldo regula- tor is disabled. the internal 1.5k has no adverse effect on device turn-on time. short-circuit protection the aat2786 contains an internal short-circuit protection circuit that will trigger when the output load current exceeds the internal threshold limit. under short-circuit conditions, the output of the ldo regulator will be cur- rent limited until the short-circuit condition is removed from the output or ldo regulator package power dissi- pation exceeds the device thermal limit. thermal protection the aat2786 has an internal thermal protection circuit which will turn on when the device die temperature exceeds 150c. the internal thermal protection circuit will actively turn off the ldo regulator output pass device to prevent the possibility of over temperature damage. the ldo regulator output will remain in a shut- down state until the internal die temperature falls back below the 150c trip point. the combination and interaction between the short cir- cuit and thermal protection systems allows the ldo regulator to withstand indefinite short-circuit conditions without sustaining permanent damage. no-load stability the aat2786 is designed to maintain output voltage regulation and stability under operational no load condi- tions. this is an important characteristic for applications where the output current may drop to zero. reverse output-to-input voltage conditions and protection under normal operating conditions, a parasitic diode exists between the output and input of the ldo regula- tor. the input voltage should always remain greater than the output load voltage, maintaining a reverse bias on the internal parasitic diode. conditions where vout might exceed vin should be avoided since this would forward bias the internal parasitic diode and allow exces- sive current flow into the vout pin, possibly damaging the ldo regulator.
17 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 in applications where there is a possibility of v out exceeding v in for brief amounts of time during normal operation, the use of a larger value c in capacitor is highly recommended. a larger value of c in with respect to c out will effect a slower c in decay rate during shut- down, thus preventing v out from exceeding v in . in appli- cations where there is a greater danger of v out exceed- ing v in for extended periods of time, it is recommended to place a schottky diode across v in to v out (connecting the cathode to v in and anode to v out ). the schottky diode forward voltage should be less than 0.45v. this ldo regulator has complete short-circuit and ther- mal protection. the integral combination of these two internal protection circuits gives the aat2786 ldo regu- lator a comprehensive safety system to guard against extreme adverse operating conditions. device power dissipation is limited to the package type and thermal dissipation properties. refer to the thermal considerations section of this datasheet for details on device operation at maximum output current loads. component selection for step-down converter inductor selection the step-down converter uses peak current mode con- trol with slope compensation to maintain stability for duty cycles greater than 50%. the output inductor value must be selected so the inductor current down slope meets the internal slope compensation requirements. the internal slope compensation for the adjustable and low voltage fixed versions is 0.75a/ s. this equates to a slope compensation that is 75% of the inductor current down slope for a 1.8v output and 1.8 h inductor. 0.75 v o m = = = 0.75 l 0.75 1.8v 1.8h a s 0.75 v o l = = = 3.3h m 0.75 3.3v 0.75 a s the inductor should be set equal to the output voltage numeric value in micro henries ( 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 satura- tion 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 losses 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 3.3 h 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 efficiency for a 1.5a, 3.3v output. input capacitor select a 10 f to 22 f x7r or x5r ceramic capacitor for the input. to estimate the required input capacitor size, determine the acceptable input ripple level (v pp ) and solve for c. the calculated value varies with input volt- age and is a maximum when v in is double the output voltage. ?? 1 - ?? v o v in c in = v o v in ?? - esr f s ?? v pp i o ?? 1 - = for v in = 2 v o ?? v o v in v o v in 1 4 c in(min) = 1 ?? - esr 4 f s ?? v pp i o always examine the ceramic capacitor dc voltage coeffi- cient characteristics when selecting the proper value. for example, the capacitance of a 10 f, 6.3v, x5r ceramic capacitor with 5.0v dc applied is actually about 6 f. the maximum input capacitor rms current is: ?? i rms = i o 1 - ?? v o v in v o v in
18 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 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. ?? 1 - = d (1 - d) = 0.5 2 = ?? v o v in v o v in 1 2 for v in = 2 v o i o rms(max) i 2 = the term ?? 1 - ?? 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 aat2786. 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 evalu- ation board input voltage pins. the inductance of these wires, along with the low-esr ceramic input capacitor, can create a high q network that may affect converter performance. this problem often becomes apparent in the form of excessive ringing in the output voltage dur- ing load transients. errors in the loop phase and gain measurements 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 sup- ply, most applications do not exhibit this problem. in applications where the input power source lead induc- tance cannot be reduced to a level that does not affect the converter performance, a high esr tantalum or alu- minum 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 pro- vides holdup during large load transitions. a 10 f to 22 f x5r or x7r ceramic capacitor typically provides sufficient bulk capacitance to stabilize the output during large load transitions and has the esr and esl charac- teristics necessary for low output ripple. the output voltage droop due to a load transient is dom- inated by the capacitance of the ceramic output capacitor. during a step increase in load current, 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: c out = 3 i load v droop f s once the average inductor current increases to the dc load level, the output voltage recovers. the above equa- tion establishes a limit on the minimum value for the output capacitor with respect to load transients. the internal voltage loop compensation also limits the minimum output capacitor value to 10 f. this is due to its effect on the loop crossover frequency (bandwidth), phase margin, and gain margin. increased output capac- itance will reduce the crossover frequency with greater phase margin. adjustable output resistor selection the output voltage on the aat2786 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 sug- gested value for r2 is 59k . although a larger value will further reduce quiescent current, it will also increase the impedance of the feedback node, making it more sensi- tive 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.
19 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 v out (v) r 2 = 59k ? r 1 (k ? ) r 2 = 221k ? r 1 (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 table 1: aat2786 resistor values for various output voltages. component selection for ldo input capacitor typically, a 1 f or larger capacitor is recommended for cin in most applications. a c in capacitor is not required for basic ldo regulator operation. however, if the aat2786 is physically located more than three centime- ters from an input power source, a c in capacitor will be needed for stable operation. c in should be located as close to the device v in pin as practically possible. c in values greater than 1 f will offer superior input line transient response and will assist in maximizing the highest possible power supply ripple rejection. ceramic, tantalum, or aluminum electrolytic capacitors may be selected for c in . there is no specific capacitor esr requirement for c in . however, for 150ma ldo regu- lator output operation, ceramic capacitors are recom- mended for c in due to their inherent capability over tantalum capacitors to withstand input current surges from low impedance sources, such as batteries in por- table devices. output capacitor for proper load voltage regulation and operational sta- bility, a capacitor is required between pins v out and gnd. the c out capacitor connection to the ldo regulator ground pin should be made as direct as practically pos- sible for maximum device performance. the aat2786 has been specifically designed to function with very low esr ceramic capacitors. for best perfor- mance, ceramic capacitors are recommended. typical output capacitor values for maximum output cur- rent conditions range from 1 f to 10 f. applications utilizing the exceptionally low output noise and optimum power supply ripple rejection characteristics of the aat2786 should use 2.2 f or greater for c out . if desired, c out may be increased without limit. in low output current applications where output load is less than 10ma, the minimum value for c out can be as low as 0.47 f. bypass capacitor and low noise applications a bypass capacitor pin is provided to enhance the low noise characteristics of the aat2786 ldo regulator. the bypass capacitor is not necessary for operation of the aat2786. however, for best device performance, a small ceramic capacitor should be placed between the bypass pin (byp) and the device ground pin (gnd). the value of c byp may range from 470pf to 10nf. for lowest noise and best possible power supply ripple rejection performance, a 10nf capacitor should be used. to practically realize the highest power supply ripple rejection and lowest out- put noise performance, it is critical that the capacitor connection between the byp pin and gnd pin be direct and pcb traces should be as short as possible. refer to the pcb layout recommendations section of this datasheet for examples. there is a relationship between the bypass capacitor value and the ldo regulator turn-on time and turn-off time. in applications where fast device turn-on and turn-off time are desired, the value of c byp should be reduced. in applications where low noise performance and/ or ripple rejection are less of a concern, the bypass capac- itor may be omitted. the fastest device turn on time will be realized when no bypass capacitor is used. dc leakage on this pin can affect the ldo regulator output noise and voltage regulation performance. for this rea- son, the use of a low leakage, high quality ceramic (npo or c0g type) or film capacitor is highly recommended.
20 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 capacitor characteristics ceramic composition capacitors are highly recommend- ed over all other types of capacitors for use with the aat2786. ceramic capacitors offer many advantages over their tantalum and aluminum electrolytic counter- parts. a ceramic capacitor typically has very low esr, is lower cost, has a smaller pcb footprint, and is non- polarized. line and load transient response of the ldo regulator is improved by using low-esr ceramic capaci- tors. since ceramic capacitors are non-polarized, they are not prone to incorrect connection damage. equivalent series resistance esr is a very important characteristic to consider when selecting a capacitor. esr is the internal series resis- tance associated with a capacitor that includes lead resistance, internal connections, size and area, material composition, and ambient temperature. typically, capac- itor esr is measured in milliohms for ceramic capacitors and can range to more than several ohms for tantalum or aluminum electrolytic capacitors. ceramic capacitor materials ceramic capacitors less than 0.1 f are typically made from npo or c0g materials. npo and c0g materials generally have tight tolerance and are very stable over temperature. larger capacitor values are usually com- posed of x7r, x5r, z5u, or y5v dielectric materials. large ceramic capacitors (i.e., greater than 2.2 f) are often available in low-cost y5v and z5u dielectrics. these two material types are not recommended for use with ldo regulators since the capacitor tolerance can vary more than 50% over the operating temperature range of the device. a 2.2 f y5v capacitor could be reduced to 1 f over temperature; this could cause prob- lems for circuit operation. x7r and x5r dielectrics are much more desirable. the temperature tolerance of x7r dielectric is better than 15%. capacitor area is another contributor to esr. capacitors that are physically large in size will have a lower esr when compared to a smaller sized capacitor of an equiv- alent material and capacitance value. these larger devic- es can improve circuit transient response when compared to an equal value capacitor in a smaller package size. consult capacitor vendor datasheets carefully when selecting capacitors for ldo regulators. thermal calculations there are three types of losses associated with the aat2786 step-down converter: switching losses, con- duction losses, and quiescent current losses. conduction losses are associated with the r ds(on) characteristics of the power output switching devices. switching losses are dominated by the gate charge of the power output switching devices. at full load, assuming continuous con- duction mode (ccm), a simplified form of the step-down converter and ldo losses is given by: p total i o 2 (r ds(on)h v obuck + r ds(on)l [v inbuck - v outbuck ]) v in(buck) = + (t sw f s i obuck + i qbuck ) v inbuck + (v inldo - v outldo ) i oldo i qbuck and i qldo are the step-down converter and ldo qui- escent currents respectively. the term t sw is used to esti- mate 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 dissipation reduces to: p total = i obuck 2 r ds(on)h + (t sw f s i buck + i qbuck ) v inbuck + (v inldo - v outldo ) i oldo since r ds(on) , quiescent current, and switching losses all vary with input voltage, the total losses should be inves- tigated over the complete input voltage range. given the total losses, the maximum junction tempera- ture can be derived from the ja for the tdfn34-16 package, which is 50c/w. t j(max) = p total ja + t amb
21 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 pcb layout the suggested pcb layout for the aat2786 is shown in figures 1 and 2. the following guidelines should be used to help ensure a proper layout. 1. the input and output capacitors (c2, c6, and c7) should connect as closely as possible to the input and output pins. 2. r1 and c3 are optional low pass filter components for the in supply pin for the buck if additional noise decupling is required in a noisy system. 3. the connection of l1 to the lx pin should be as short as possible. 4. the feedback trace or fb pin should be separated from any power trace and connect as closely as pos- sible to the load point. sensing along a high-current load trace will degrade dc load regulation. 5. 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 differ- ences in the potential of the internal signal ground and the power ground. 6. connect unused signal pins to ground to avoid unwanted noise coupling. 7. for low output noise and highest possible power sup- ply ripple rejection performance, it is critical to con- nect the bypass capacitor (c8) and output capacitor (c7) directly to the ldo regulator ground pin. this method will eliminate any load noise or ripple current feedback through the ldo regulator. 8. for good thermal coupling, pcb vias are required from the pad for the tdfn paddle to the bottom ground plane.
22 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 printed circuit board layout recommendations figure 1: aat2786 evaluation board component side layout. figure 2: aat2786 evaluation board solder side layout.
23 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 3.3h l1 c1 opt c5 opt buck out ldo out ldo in buck in c2 10f c3 1f c6 1f c8 10nf c7 2.2f c4 22f r1 100 r2 adj r3 59k vin 12 mode/sync 14 vp 16 vp 15 ldoin 11 buck_en 13 ldo_en 9 n/c 10 ldoout 6 byp 8 lx 2 lx 1 gnd 4 pgnd 3 ldo_gnd 7 fb 5 aat2786irn en ldo mode/sync u1 tdfn34-16 figure 3: aat2786 evaluation board schematic.
24 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 step-down converter design example specifications v obuck = 3.3v @ 1.5a, pulsed load ? i load = 1.5a v oldo = 2.5v @ 150ma v in = 2.7v to 4.2v (3.6v nominal) f s = 1.2mhz m = 0.75a/ s t amb = 85c in tdfn34-16 package 3.3v buck output inductor 0.75 v o l = = = 3.3h (see table 2) m 0.75 3.3v 0.75 a s for sumida inductor cdrh4d28, 3.3 h, dcr = 49.2m max. v obuck v obuck 3.3 v 3.3v i = 1 - = 1 - = 179m a l1 f s v inbuck 3.3h 1.2mhz 4.2v i pk = i obuck + i 1 = 1.5a + 0.089a = 1.59a 2 p l1 = i outbuck 2 dcr = 1.5a 2 49.2m = 110mw 3.3v buck 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 rms = esr i rms 2 = 5m (52ma) 2 = 13.3w 3.3v buck input capacitor input ripple v pp = 50mv c in = = = 7.3f; use 10f 1 - esr 4 f s v pp i obuck 1 - 5m 4 1.2mhz 50mv 1.5a i obuck rms(max) i p = esr (i rms 2 ) = 5m (0.75a) 2 = 3mw 2 = = 0.75arms
25 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 aat2786 losses total losses can be estimated by calculating the dropout (v in = v obuck ) 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 temperature with the tdfn 50c/w package. p total = i obuck 2 r ds(on)h + (v inldo - v outldo ) i oldo = 1.5a 2 0.16 + (4.2 - 2.5) 150ma = 615mw t j(max) = t amb + ja p loss = 85 c + (50 c/w) 615mw = 116 c 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. p total = 1.5a 2 152m + (5ns 1.2mhz 1.5a + 50a) 3.6v + (4.2v - 2.5v) 150m a = 630mw = i obuck 2 r ds(on)h + (t sw f s i buck + i qbuck ) v inbuck + (v inldo - v outldo ) - i oldo t j(max) = t amb + ja p loss = 85 c + (50 c/w) 6300mw = 117 c v out (v) inductance ( h) part number manufacturer size (mm) rated current (a) i rms (a) i sat (a) dcr ( ? ) 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 table 2: surface mount inductors. manufacturer part number value voltage temp. co. case murata grm21br60j106ke19 10 f 6.3v x5r 0805 murata grm21br60j226me39 22 f 6.3v x5r 0805 table 3: surface mount capacitors.
26 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 ordering information package part marking 1 ldo output voltage part number (tape and reel) 2 tdfn34-16 3kxyy e = 1.2v AAT2786IRN-AE-T1 skyworks green? products are compliant with all applicable legislation and are halogen-free. for additional information, refer to skyworks de?ition of green , document number sq04-0074. package information tdfn34-16 3 3.000 all dimensions in millimeters. 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 required to ensure a proper bottom solder connection.
27 aat2786 1.5a step-down converter and 150ma ldo data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202046b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 copyright ? 2012, 2013 skyworks solutions, inc. all rights reserved. information in this document is provided in connection with skyworks solutions, inc. (?skyworks?) products or services. these m aterials, including the information contained herein, are provided by skyworks as a service to its customers and may be used for informational purposes only by the customer. skyworks assumes no responsibility fo r errors or omissions in these materials or the information contained herein. sky- works may change its documentation, products, services, speci cations or product descriptions at any time, without notice. skyworks makes no commitment to update the materials or informati on and shall have no responsibility whatsoever for con icts, incompatibilities, or other dif culties arising from any future changes. no license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document . skyworks assumes no liability for any materials, products or information provided here- under, including the sale, distribution, reproduction or use of skyworks products, information or materials, except as may be p rovided in skyworks terms and conditions of sale. the materials, products and information are provided ?as is? without warranty of any kind, whether express, implied, statutory, or otherwise, including fitness for a particular purpose or use, merchantability, performance, quality or non-infringement of any intellectual property right; all such warranti es are hereby expressly disclaimed. skyworks does not warrant the accuracy or completeness of the information, text, graphics or other items contained within these materials. sk yworks shall not be liable for any damages, in- cluding but not limited to any special, indirect, incidental, statutory, or consequential damages, including without limitation , lost revenues or lost profits that may result from the use of the materials or information, whether or not the recipient of materials has been advised of the possibility of such damage. skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the skyworks products could lead to personal injury, death, physical or en- vironmental damage. skyworks customers using or selling skyworks products for use in such applications do so at their own risk and agree to fully indemnify skyworks for any damages resulting from such improper use or sale. customers are responsible for their products and applications using skyworks products, which may deviate from published speci cations as a result of design defects, errors, or operation of products outside of pub- lished parameters or design speci cations. customers should include design and operating safeguards to minimize these and other risks. skyworks assumes no liabi lity for applications assistance, customer product design, or damage to any equipment resulting from the use of skyworks products outside of stated published speci cations or parameters. skyworks, the skyworks symbol, and ?breakthrough simplicity? are trademarks or registered trademarks of skyworks solutions, inc ., in the united states and other countries. third-party brands and names are for identi cation purposes only, and are the property of their respective owners. additional information, including relevant terms and co nditions, posted at www.skyworksinc.com, are incorporated by reference.

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