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1 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet general description the aat1171 switchreg? dynamically controls the oper- ating voltage of a wcdma or cdma power amplifier inside single-cell, lithium-ion battery-powered systems. the aat1171 outputs a voltage between 0.6v and 3.6v, thereby optimizing the amplifier efficiency at both low and high transmit levels. the aat1171 output voltage is controlled via an analog signal from the baseband processor. it can deliver 600ma of continuous load current while maintaining a low 45 a of no load quiescent current. the 2mhz switch- ing frequency minimizes the size of external components while keeping switching losses low. to further improve system efficiency, an 85m bypass mosfet transistor is also included to allow the pa to be powered directly from the battery. the aat1171 maintains high efficiency thoughout the entire load range in light load (ll) mode, and can be forced into pulse wide modulation (pwm) mode for low noise operation or can be synchronized to an external clock. the aat1171 is available in a pb-free, space-saving tdfn33-12 or 12-pin wafer-level chip scale package (wlcsp) and is rated over the -40c to +85c tempera- ture range. features ? v in range: 2.7v to 5.5v ? variable output voltage: 0.6v to 3.6v ? 600ma output current ? dac input: 0.2v to 1.2v ? high output accuracy: 3% ? 45 a no load quiescent current ? internal soft start limits startup current and output voltage overshoot ? synchronizable to external 19.8mhz system clock ? over-temperature and current limit protection ? integrated 85m bypass mosfet ? 2mhz operation ? pwm/ll control with override ? fast start-up: ? 50 s (aat1171-4, aat1171-5) ? 150 s (aat1171-1) ? 100% duty cycle operation ? <30 s output voltage response time ? 3x3mm 12-pin tdfn or 1.535x2.235mm 12-pin wlcsp package ? temperature range: -40c to +85c applications ? wcdma or cdma pa in cellular phones, smartphones, feature phones, etc. ? express card ? pcmcia data cards typical application aat1171-1/ aat1171-4 pa v ref v cc2 v cc2 v cont baseband processor tx rx dac 0.6v - 3.6v lx vout gndx2 dac vin 4.7f 4.7f 2.2h en mode/sync bypass vcc C c in c out l1 aat1171-5 pa v ref v cc2 v cc2 v cont baseband processor tx rx dac 0.6v - 3.6v lx vout gndx2 dac vin 4.7f 10f 4.7h en mode/sync bypass vcc C c in c out l1
2 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet pin descriptions pin # symbol function tdfn33-12 wlcsp-12 1 n/a n/c not connected. 2, 3 5, 9 vout feedback input pin. this pin is connected to the converter output. it is used to complete the control loop, regulating the output voltage to the desired value. when in bypass mode, a low resistance mosfet is connected between this pin and vin. 4 7 vcc bias supply. supply power for the internal circuitry. connect to input power via low pass lter with decoupling to agnd. 5 6 agnd analog ground. connect the return of all small signal components to this pin. 6 1 dac control voltage input from a dac. input voltage between 0.2v and 1.2v to con- trol output voltage of the converter. force pin to 1.3v for bypass switch enable. 7 2 en enable dc/dc converter, active high. 8 3 bypass enable control to bypass the dc/dc converter when pa transmitting at full power from low battery voltage. active high. 9 4 mode/sync this pin is used to program the device between pwm and ll mode: high - pwm mode only low - ll mode: pwm operation for loads above 100ma and variable switching frequency for loads below 100ma. connecting the sync pin to the system clock (19.8mhz) will override the internal clock and force the switching frequency to the external clock frequency divided by 10. 10 12 vin input supply voltage for the converter. must be closely decoupled. 11 8, 11 pgnd main power ground. connect to the output and input capacitor return. 12 10 lx switching node. connect the inductor to this pin. it is connected internally to the drain of both low- and high-side mosfets. ep n/a exposed paddle (bottom). connect to ground directly beneath the package. pin configuration tdfn33-12 wlcsp-5 (top view) (top view) n/c vout vout 1 vcc a gnd dac lx pgnd vin mode/sync bypass en 2 3 4 5 6 12 11 10 9 8 7 12 11 10 7 8 9 6 5 4 1 2 3 vin vcc agnd dac 5: vout 2: en 11: pgnd 8: pgnd lx vout mode/sync bypass
3 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet absolute maximum ratings 1 symbol description value units v cc , v in input voltage and bias power to gnd 6.0 v v lx lx to gnd -0.3 to v in + 0.3 v v out vout to gnd -0.3 to v in + 0.3 v v n en, dac, bypass, mode/sync 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 thermal information 2 symbol description value units p d maximum power dissipation, t a = 25c tdfn33-12 2, 3 2.0 w wlcsp-12 2, 4 0.88 ja thermal resistance, t a = 25c tdfn33-12 50 c/w wlcsp-12 114 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at c onditions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one time. 2. mounted on fr4 board; for the wlcsp package, use the nsmd (none-solder mask defined) pad style for tighter control on the co pper etch process. 3. derate 20mw/c above 25c ambient. 4. derate 8.8mw/c above 25c ambient.
4 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet electrical characteristics 1 t a = -40c to +85c, unless otherwise noted. v in = v cc = 3.6v; typical values are t a = 25c. symbol description conditions min typ max units v in input voltage 2.7 5.5 v v uvlo uvlo threshold v in rising 2.6 v uvlo hysteresis 200 mv v out v out programmable range 0.6 3.6 v v dacin input voltage range from dac 0.2 1.2 v i q quiescent current no load, light load 45 70 a no load, pwm, v cc bias current 420 i shdn shutdown current en = agnd = pgnd, mode/sync = v in or gnd 1.0 a i lim p-channel current limit t a = 25c 1.2 1.6 a r ds(on)h high side switch on resistance 230 m r ds(on)l low side switch on resistance 230 m r ds(on)bp bypass switch resistance v dac = 1.3v or bypass = vin 85 m i lxleak lx leakage current v cc = 5.5v, v lx = 0 to v cc , en = 0v 1 a ? v out / v out load regulation i load = 0 to 500ma 0.5 % ? v out / v out / ? v in line regulation 0.2 %/v r out feedback impedance 170 k v out output voltage accuracy v dac = 0.6v, i load = 0 1.746 1.8 1.854 v f osc oscillator frequency 2.0 mhz t sd over-temperature shutdown threshold 140 c t hys over-temperature shutdown hysteresis 15 c i ll light load load current threshold 100 ma t vouts output voltage settling time v out = 0.6v to v out(max) , mode/sync = v in 30 s pwm/light load/en v en(l) enable threshold low 0.6 v v en(h) enable threshold high 1.4 v i en input low current v cc = 5.5v -1.0 1.0 a t en turn-on enable response time aat1171-1: en = low to high, mode/sync = high, v dac = 1.2v 150 s aat1171-4/aat1171-5: en = low to high, mode/sync = high, v dac = 1.2v 50 mode/sync f mode/sync synchronization frequency sync to 19.8mhz 2 19.8 mhz v mode/ sync(h) mode/sync high level threshold v in - 0.4 v v mode/ sync(l) mode/sync low level threshold 0.4 v i mode/sync mode/sync low current v sync = gnd or v cc -1.0 1.0 a dac input gain output voltage/dac voltage 3 3 v/v 1. the aat1171 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. 2. please contact sales for other synchronization frequencies. 3. please contact sales for other output voltage/dac voltage gains.
5 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet typical characteristics efficiency vs. output current (ll mode; v out = 3.3v) output current (ma) efficiency (%) 40 50 60 70 80 90 100 0.1 1 10 100 1000 v in = 5.0v v in = 4.2v v in = 3.9v load regulation (ll mode; v out = 3.3v) output current (ma) output voltage error (%) -1.0 -0.5 0.0 0.5 1.0 0.1 1 10 100 1000 v in = 5.0v v in = 4.2v v in = 3.6v efficiency vs. output current (pwm mode; v out = 3.3v) output current (ma) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 v in = 3.6v v in = 5.0v v in = 4.2v load regulation (pwm mode; v out = 3.3v) output current (ma) output voltage error (%) -1.0 -0.5 0.0 0.5 1.0 0.1 1 10 100 1000 v in = 5.0v v in = 4.2v v in = 3.6v efficiency vs. output current (ll mode; v out = 2.5v) output current (ma) efficiency (%) 40 50 60 70 80 90 100 0.1 1 10 100 1000 v in = 3.0v v in = 4.2v v in = 5.0v load regulation (ll mode; v out = 2.5v) output current (ma) output voltage error (%) -1.0 -0.5 0.0 0.5 1.0 0.1 1 10 100 1000 v in = 5.0v v in = 4.2v v in = 3.0v
6 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet typical characteristics 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 0.1 1 10 100 1000 v in = 3.0v v in = 4.2v v in = 5.0v load regulation (pwm mode; v out = 2.5v) output current (ma) output voltage error (%) -1.0 -0.5 0.0 0.5 1.0 0.1 1 10 100 1000 v in = 5.0v v in = 4.2v v in = 3.0v efficiency vs. output current (ll mode; v out = 1.8v) output current (ma) efficiency (%) 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 v in = 2.7v v in = 4.2v v in = 3.6v load regulation (ll mode; v out = 1.8v) output current (ma) output voltage error (%) -1.0 -0.5 0.0 0.5 1.0 0 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 0.1 1 10 100 1000 . v in = 2.7v v in = 3.6v v in = 4.2v load regulation (pwm mode; v out = 1.8v) output current (ma) output voltage error (%) -1.0 -0.5 0.0 0.5 1.0 0.1 1 10 100 1000 v in = 3.6v v in = 4.2v v in = 2.7v
7 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet typical characteristics output voltage vs. supply voltage (ll mode; v out = 1.5v) supply voltage (v) output voltage (v) 1.494 1.498 1.502 1.506 1.510 1.514 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 i out = 50ma i out = 300ma i out = 600ma output voltage vs. supply voltage (pwm mode; v out = 1.5v) supply voltage (v) output voltage (v) 1.494 1.498 1.502 1.506 1.510 1.514 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 i out = 50ma i out = 300ma i out = 600ma output voltage vs. temperature (v in = 3.6v; v out = 1.8v; v dac = 0.6v; r l = 10) temperature ( c) output voltage error (%) -1.5 -1.0 -0.5 0.0 0.5 1.0 -40 -15 10 35 60 85 bypass mode dropout voltage vs. load current load current (ma) dropout voltage (v) -0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.05 0.1 1 10 100 1000 supply current vs. supply voltage (no load; ll 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 v out = 1.8v v out = 0.6v supply current vs. supply voltage (no load; pwm mode) supply voltage (v) supply current (ma) 3.0 3.5 2.0 2.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 v out = 1.8v v out = 0.6v
8 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet typical characteristics p-channel r ds(on) vs. input voltage input voltage (v) r ds(on) (m ) 2.7 3.1 3.5 3.9 4.5 4.9 5.5 2.9 3.3 3.7 4.1 4.3 4.7 5.1 5.3 0 50 100 150 200 250 300 350 400 t j = 120 c t j = 85 c t j = 25 c bypass r ds(on) vs. input voltage input voltage (v) r ds(on) (m ) 0 20 40 60 80 100 120 140 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 t j = 25 c t j = 85 c t j = 120 c switching frequency vs. temperature (v in = 3.6v; v out = 1.8v; r l = 10) temperature ( c) switching frequency (mhz) 1.90 1.92 1.94 1.96 1.98 2.00 2.02 2.04 2.06 -40.0 -20.0 0.0 20.0 40.0 60.0 80.0 ll pwm output voltage vs. dac voltage (v in = 4.2v; ll mode) dac voltage (v) output voltage (v) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 0.2 0.4 0.6 0.8 1.0 1.2 1.4 25 c 85 c -40 c heavy load switching waveform (v in = 3.6v; v out = 1.8v; r l = 3 ; c out = 4.7f; l = 2.2h) time (200ns/div) v out (ac coupled) 20mv/div i l 200ma/div v lx 2v/div 0 0
9 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet typical characteristics light load switching waveform (pwm mode; v in = 4.2v; v out = 0.6v; r l = 10 ; c out = 4.7f; l = 2.2h) time (200ns/div) v out (ac coupled) 20mv/div i l 100ma/div v lx 2v/div 0 0 light load switching waveform (ll mode; v in = 4.2v; v out = 0.6v; r l = 10 ; c out = 4.7f; l = 2.2h) time (1s/div) v out (ac coupled) 20mv/div i l 200ma/div v lx 2v/div 0 0 dac transient response in pwm mode (v in = 3.6v; r l = 10 ; c out = 4.7f; l = 2.2h) time (25s/div) v out 1v/div v dac 0.5v/div 0 0 3.3v 0.6v 1.2v 0.2v dac transient response in ll mode (v in = 3.6v; r l = 10 ; c out = 4.7f; l = 2.2h) time (25s/div) v out 1v/div v dac 0.5v/div 0 0 3.3v 0.6v 1.2v 0.2v bypass transient response (pwm mode; v in = 3.6v; r l = 10 ; c out = 4.7f; l = 2.2h) time (25s/div) v out 1v/div v byp 1v/div 0 0 3.5v 0.6v bypass transient response (ll mode; v in = 3.6v; r l = 10 ; c out = 4.7f; l = 2.2h) time (25s/div) v out 1v/div v byp 1v/div 0 0 3.5v 0.6v
10 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet typical characteristics dac to bypass transient response (ll mode; v in = 4.2v; r l = 10 ; c out = 4.7f; l = 2.2h) time (25s/div) v out 1v/div v dac 0.5v/div 0 0 0.6v 4.2v 1.3v 0.2v enable soft start (v in = 3.6v; v out = 1.8v; r l = 3.9 ; c out = 4.7f; l = 2.2h) time (20s/div) v out 1v/div enable 2v/div i in 200ma/div 0v 0v 0a 1.8v load transient response (v in = 4.2v; v out = 3.3v; c out = 4.7f; l = 2.2h) time (20s/div) v out (ac coupled) 20mv/div i out 200ma/div 525ma 250ma 3.51v 3.26v load transient response (v in = 3.6v; v out = 1.8v; c out = 4.7f; l = 2.2h) time (20s/div) v out (ac coupled) 20mv/div i out 100ma/div 200ma 500ma 1.914v 1.798v line transient response (v out = 1.5v; r l = 10 ; c out = 4.7f; l = 2.2h) time (50s/div) v out (ac coupled) 50mv/div v in 0.5v/div 3.6v 3.0v 1.56v 1.44v
11 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet functional description the aat1171 is a 600ma 2mhz peak current mode syn- chronous step-down (buck) converter designed to oper- ate from a single-cell lithium-ion battery with a 2.7v to 4.2v input range. the output voltage is dynamically programmed by the dac input voltage. to maximize converter efficiency over all load conditions, the converter automatically transitions to a variable fre- quency light load (ll) mode when the load is less than 100ma. when combined with the very low quiescent current, the ll mode maintains a high efficiency over the complete load range. for noise sensitive applications, the converter can be forced into a fixed frequency pwm mode. provisions are also made for synchronization of the converter to an external system clock. the synchronous buck converter power output devices are sized at 230m for a 600ma full load output current. in addition to the converter output, an additional low resistance bypass mosfet (85m ) can be connected between the battery input and the converter output (v in to v out ), bypassing the converter and output inductor to improve headroom and extend the wcdma pa full power range. this reduces the battery voltage necessary for a wcdma rf power amplifier to meet linearity require- ments, thus extending operating time. in dual mode systems, the bypass mode may also be used when the wcdma rf power amplifier is in gsm mode. bypass mode is activated by setting the bypass input high or by forcing the baseband dac output voltage to 1.3v. the aat1171 requires only three external components for operation (c in , c out , l x ). the high 2mhz switching frequency reduces the inductor size required to 2.2 h for the aat1171-1/aat1171-4 and 4.7 h for the aat1171-5. this reduces the dc resistance and improves the converter efficiency while minimizing the inductor functional block diagram logic dh dl comp error amp vout vcc vin l x agnd pgnd dac en bypass mode/sync mode/sync interface
12 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet footprint and height. the output voltage of the converter is regulated to within 0.5% and will settle in less than 30 s (according to wcdma specifications) in response to any step change in the dac input. under-voltage lockout, internal compensation, soft-start, over-current, and over-temperature protection are also included. dac output voltage control the output voltage is programmed by way of the dac input voltage. the dac to output gain for the aat1171 is 3. v out = 3 v dac the dac input voltage range is 0.2v to 1.2v, which cor- responds to an output voltage range of 0.6v to 3.6v (see figure 1). for a 1.3v dac level, the bypass switch is activated and the output voltage level is equivalent to the input voltage minus the bypass mosfet (r ds(on)(bp) ) drop. bypass mode in bypass mode, the aat1171 bypasses the output inductor, connecting the input directly to the output through a low r ds(on) 85m mosfet. bypass mode is initiated by applying 1.3v to the dac input or by apply- ing a logic high to the bypass input. when not activated, a logic level low must be applied to the bypass input pin. the bypass mosfet current is limited to 600ma. ll/pwm control two control modes are available with the aat1171: ll mode and pwm mode. pwm mode maintains a fixed switching frequency regardless of load. the fixed switch- ing frequency gives the advantage of lower output ripple and simplified output and input noise filtering. pwm mode also provides a faster output voltage response to changes in the dac voltage. in ll mode, the converter transitions to a variable switching frequency as the load decreases below 100ma. above 100ma, where switching losses no longer domi- nate, the switching frequency is fixed. the ll mode?s effect on the dac to output voltage response time is most notable when transitioning from a high output volt- age to a low voltage. when the converter is in pwm mode, the inductor current can be reversed and the out- put voltage actively discharged by the synchronous mosfet. while in ll mode, the output voltage is dis- charged by the load only, resulting in a slower response to a dac transition from a high to a low voltage. for pwm mode, apply a logic level high to the mode/ sync pin; for ll mode, apply a logic level low to the mode/sync pin. soft start/enable the aat1171 soft-start control prevents output voltage overshoot and limits inrush current when either the input power or the enable input is applied. when pulled low, the enable input forces the converter into a low-power, non-switching state with less than 1 a bias current. 1v 2v 3v 4v 3.6v 1v 1.2v dac output output to pa 0.6v 0.2v v in 1.3v bypass mode figure 1: v out vs. v dac .
13 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet low dropout operation for conditions where the input voltage drops to the out- put voltage level, the converter duty cycle increases to 100%. as 100% duty cycle is approached, the minimum off-time initially forces the high-side on-time to exceed the 2mhz clock period, reducing the converter switching frequency. once the input drops to the level where the output can no longer be regulated, the high-side p-channel mosfet is enabled continuously for 100% duty cycle. the output voltage then tracks the input voltage minus the ir drop of the high side p-channel mosfet r ds(on) . uvlo shutdown under-voltage lockout (uvlo) circuitry monitors the input voltage and disables the converter when the input voltage drops to 2.4v, guaranteeing sufficient operating input voltage to maintain output voltage regulation and control. for a rising input voltage, the uvlo circuitry enables the converter 200mv above the shutdown level at 2.6v. current limit and short-circuit protection the high-side p-channel mosfet current limit compara- tor limits the peak inductor current to 1.6a. in pwm mode, the synchronous mosfet current limit compara- tor limits the peak negative inductor current, and output capacitor discharge current is limited to 1a. in bypass mode, the bypass mosfet current is limited to 600ma. in the event of an overload or short-circuit condition, the current limit protects the load and the aat1171 power devices. upon removal of the short-circuit or fault condi- tion, the aat1171 output automatically recovers to the regulated level. thermal overload protection the maximum junction temperature is limited by the aat1171 over-temperature shutdown protection circuit- ry. both the step-down converter and the bypass mosfet are disabled when the junction temperature reaches 140c. normal operation resumes once the junction temperature drops to 125c. external synchronization the aat1171 switching frequency can be synchronized to an external square wave clock via the mode/sync input. the external clock frequency range and logic levels for which the aat1171 will remain synchronized are listed in the electrical characteristics table of this datasheet. applications information inductor selection the step-down converter uses peak current mode con- trol with slope compensation to maintain stability for duty cycles greater than 50%. because the required slope compensation varies with output voltage, the aat1171 varies the slope compensation to match the output voltage. this allows the use of a single inductor value for all output voltage levels. the inductor value is 2.2 h for the aat1171-1/aat1171-4 and 4.7 h for the aat1171-5. 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. the inductor ripple cur- rent varies with both the input voltage and the output voltage and peaks at the maximum input voltage with the output at one half of the input voltage. for the typi- cal aat1171, this corresponds to a 4.2v input voltage and a 2.1v output voltage. with the suggested 2.2 h inductor, this corresponds to 239ma peak-to-peak ripple current. for a 600ma dc load current, the peak inductor current would be 718ma. in order to prevent saturation under normal load conditions, the peak inductor current should be less than the inductor saturation current. v in(max) 8 ? l ? f s 4.2v 8 ? 2.2h ? 2mhz i pk(max) = i o + = 0.6a + = 0.6a + 0.12a = 0.72a some inductors may meet peak and average current requirements 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 inductor losses can be esti- mated by using the full load output current. the output inductor losses can then be calculated to estimate their effect on overall device efficiency.
14 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet p o p o + pl 3.4 ? 0.6a 3.4v ? 0.6a + 50mw = = = 97% pl = i o 2 ? dcr = 0.6a 2 ? 0.14 = 50mw the 2.2 h inductor selected for the aat1171 evaluation board has a 140m dcr and a 0.91a dc current rating. at 600ma load current, the inductor loss is 50mw which gives 2.4% loss in efficiency for a 600ma 3.4v output voltage with an inductor that measures 3.2x3.2x1.2mm. output capacitor selection the aat1171-1/aat1171-4 are designed for use with 4.7 f 10v x5r ceramic output capacitors, while the aat1171-5 is designed for use with 10 f 10v x5r ceramic output capacitors. although a larger output capacitor provides improved response to large load tran- sients, it also limits the output voltage rise and fall time in response to the dac input. for stable operation, with sufficient phase and gain margin, the internal voltage loop compensation limits the minimum output capacitor value to 4.7 f. increased output capacitance will reduce the crossover frequency with greater phase margin. the output voltage droop due to load transients is dom- inated by the output capacitor. during a step increase in load current, the output capacitor supplies the load cur- rent while the control loop responds. within two or three switching cycles, the inductor current increases to match the load current demand. the relationship of the output voltage 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 output capacitor value necessary to meet a given output voltage droop requirement (v droop ) for a given load transient. the maximum output capacitor rms ripple current is: 1 23 v out (v in(max) - v out ) rms(max) i l f s v in(max) = dissipation due to the rms current in the ceramic output capacitor esr is typically minimal, resulting in less than a few degrees rise in hot-spot temperature. input capacitor selection a 10v x5r or x7r ceramic capacitor is suggested for the input capacitor with typical values ranging from 4.7 f to 10 f. to estimate the required input capacitance size, determine the acceptable input ripple level (v pp ) and solve for c, as shown below. 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 proper value. for example, due to the voltage coefficient of a 10 f 6.3v x5r ceramic capacitor, with an applied voltage of 5v dc the capacitance decreases to 6 f. ?? 1 - ?? v o v in c in = v o v in ?? - esr f s ?? v pp i o ?? 1 - = ?? v o v in v o v in 1 4 c in(min) = 1 ?? - esr 4 f s ?? v pp i o the maximum input capacitor rms current is: ?? i rms = i o 1 - ?? v o v in v o v in 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 - ?? v o v in v o v in appears in both the input voltage ripple and input capacitor rms current equations and is a maximum when v in is twice v o ; therefore, the input voltage ripple and the input capacitor rms current ripple are a maximum at 50% duty cycle.
15 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet the input capacitor provides a low impedance loop for the edges of pulsed current drawn by the aat1171. low esr/esl x7r and x5r ceramic capacitors are ideal for this function. to minimize stray inductance, the capaci- tor 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 figure 4. a laboratory test set-up typically consists of two long wires running from the bench power supply to the eval- uation 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 with errors in loop phase and gain measurements. 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 induc- tance cannot be reduced to a level that does not affect the converter performance, a high esr tantalum or alu- minum electrolytic capacitor (c3 of figure 5) should be placed in parallel with the low esr, esl bypass ceramic capacitor. this dampens the high q network and stabi- lizes the system. dac programming gain the output voltage is dynamically controlled by the dac input voltage. the dac to output gain is fixed at 3. the typical response time for a 0.2v to 1.2v pulsed signal on the dac input is less than 30 s. the dac gain can be reduced by an external resistive divider at the dac input, as shown in the evaluation board schematic in figures 2 and 3. for a dac to output gain of 2 and r2 at 10k , r1 is 4.99k . (3- g dac )r2 g dac (3 - 2)10k 2 r1 = = = 4.99k thermal calculations there are three types of losses associated with the aat1171 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 mosfet devices. switching losses are domi- nated by the gate charge of the power mosfet devices. the aat1171 main and synchronous power mosfets are sized to have similar r ds(on) values that track with the input voltage. at full load, assuming continuous conduc- tion mode (ccm), a simplified form of the step-down converter losses is given by: p total = i o 2 r ds(on) + (t sw f s i o + i q ) v in i q is the step-down converter quiescent current. the term t sw is used to estimate the full load switching loss- es, which are dominated by the gate charge losses. for the condition where the buck converter is at 100% duty cycle dropout, the total device dissipation reduces to: p total = i o 2 r ds(on) + i q v in in bypass mode, the bypass mosfet r ds(on)(bp) is used to determine the losses. the power mosfet r ds(on) increas- es with decreasing input voltage and the associated losses are a maximum at the minimum input voltage (2.7v). p total = i o 2 r ds(on)(bp) + i q v in since the 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. after calculating the total losses, the maximum junction temperature can be derived from the ja for the tdfn33- 12 package which is typically 50c/w. t j(max) = p total ja + t amb
16 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet 2.2h l1 4.7f c2 bypass 4.7f c1 1 2 3 32 1 12 3 enable v out dac vout 2 n/c 1 pgnd 11 en 7 bypass 8 vin 10 vout 3 lx 12 mode/sync 9 dac 6 agnd 5 vcc 4 aat1171-1/aat1171-4 u1 v in gnd sync r1 r2 gnd pwm ll on off on off figure 2: aat1171-1/aat1171-4 evaluation board schematic. 4.7h l1 10f c2 bypass 4.7f c1 1 2 3 32 1 12 3 enable v out dac vout 2 n/c 1 pgnd 11 en 7 bypass 8 vin 10 vout 3 lx 12 mode/sync 9 dac 6 agnd 5 vcc 4 aat1171-5 u2 v in gnd sync r1 r2 gnd pwm ll on off on off figure 3: aat1171-5 evaluation board schematic.
17 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet wlcsp package light sensitivity the electrical performance of the wlcsp package can be adversely affected by exposing the device to certain light sources such as direct sunlight or a halogen lamp whose wavelengths are red and infra-reds. however, fluores- cent lighting has very little effect on the electrical per- formance of the wlcsp package. layout the suggested pcb layout for the aat1171 is shown in figures 4 and 5. the following guidelines should be used to ensure a proper layout. 1. the input capacitor (c1) should connect as closely as possible to vin (pin 10) and pgnd (pin 11). 2. c2 and l1 should be connected as closely as possi- ble. the connection of l1 to the lx pin should be as short as possible. 3. the pcb trace connected to vout (pins 2 and 3) is tied to the bypass path, as well as the feedback path for the control loop. in bypass mode, the full load current is delivered directly from the battery input; therefore, this trace should be sufficient to handle current up to the bypass current limit level. 4. the resistance of the trace from the load return to pgnd (pin 11) should be kept to a minimum. this minimizes any error in dc regulation due to differ- ences in the potential of the internal signal ground and the power ground. 5. for good thermal coupling, pcb vias are required from the pad for the tdfn exposed paddle to the ground plane. the via diameter should be 0.3mm to 0.33mm and positioned on a 1.2mm grid. figure 4: aat1171 evaluation board figure 5: aat1171 evaluation board top side layout. bottom side layout.
18 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet pa step-down converter design example specifications v o(buck) 0.6v to 3.4v with r l =10 v in 2.7v to 4.2v (3.6v nominal) f s 2.0mhz t amb 85c output inductor l1 = 2.2 h for copper electronics sd3112, 2.2 h, dcr = 140m . v o v o 2.1 v 2.1v i l1(max) = ? 1 - = ? 1 - = 239m a l ? f s v in 2.2h ? 2.0mhz 4.2v ? ? ? ? ? ? ? ? the maximum inductor ripple current occurs at 50% duty cycle at the maximum input voltage. i pkl1 = i o + i l1(max) = 0.6a + 0.118a = 0.718 a 2 p l1 = i o 2 ? dcr = 0.6a 2 ? 140m = 50mw output capacitor specify that v droop = 0.2v for a 600ma load pulse. 1 23 1 3.4v (4.2v - 3.4v) 4.7h 2.0mhz 4.2v 23 rms i l1 f s v in(max) = 3 i load v droop f s 3 0.6a 0.2v 2.0mhz c out = = = 4.5f = 69marms (v o ) (v in(max) - v o ) = p esr = esr i rms 2 = 5m (69ma) 2 = 24w input capacitor specify a maximum input voltage ripple of v pp = 25mv. c in(min) = = = 3.4f 1 ?? - esr 4 f s ?? v pp i o 1 ?? - 5m 4 2.0mhz ?? 25mv 0.6a i o rms i p = esr i rms 2 = 5m (0.3a) 2 = 0.45mw 2 = = 0.3arms
19 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet aat1171 losses p total = 0.6 2 0.29 + (5ns 2.0mhz 0.6a + 60a) 4.2v = 104m w = i o 2 r ds(on) + (t sw f s i o + i q ) v in t j(max) = p total ja + t amb = 104mw 50 c/w = 5.2 c + 70 c = 75.2 c aat1171 dropout losses p total = 0.6 2 310m + 100a 3.5v = 112mw = i o 2 r ds(on)(hs) + i q v in t j(max) = p total ja + t amb = 112mw 50 c/w = 5.6 c + 70 c = 75.6 c
20 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet manufacturer value device voltage case size part number avx www.avxcorp.com 10 f output capacitor 10v 0805 0805zd106kat murata www.murata.com 4.7 f output or input capacitor 10v 0805 grm21br61a475ka73l input capacitor 6.3v 0603 grm188r60j475ke19d 10 f output capacitor 10v 0805 grm21br61a106k tdk www.tdk.com 4.7 f output or input capacitor 10v 0805 c2012x5r1a475k input capacitor 6.3v 0603 c1608x5roj475k 10 f output capacitor 10v 0805 c2012x5r1a106k taiyo yuden www.t-yuden.com 4.7 f output or input capacitor 10v 0805 lmk212bj475mg input capacitor 6.3v 0603 jmk107bj475ma manufacturer value i sat i rms dcr case size (mm) part number cooper electronics www.cooperet.com 2.2 h 1.12a 0.91a 140m 3.1x3.1x1.2 sd3118-2r2 4.7 h 0.8a 0.74a 246m 3.1x3.1x1.2 sd3112-4r7-r sumida www.sumida.com 2.2 h 1.1a 1.3a 96m 3.2x3.2x1.2 cdrh2d11/hp 4.7 h 0.75a 0.85a 238m 3.2x3.2x1.2 cdrh2d11/hp abco electronics www.abco.co.kr 2.2 h 0.52a 200m 2.0x2.0x1.0 lpf2010-2r2m 2.2 h 0.55a 110m 2.0x2.0x1.4 lpf2010-2r2m table 1: suggested component selection.
21 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet ordering information package marking 1 part number (tape and reel) 2 tdfn33-12 rxxyy aat1171iwp-1-t1 tdfn33-12 xcxyy aat1171iwp-4-t1 tdfn33-12 xdxyy aat1171iwp-5-t1 wlcsp-12 ugyw 3 AAT1171IUP-1-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 4 tdfn33-12 top view bottom view detail "a" side view 3.00 all dimensions in millimeters. 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 3. yw = data code (year, week) for wlcsp-12 package. 4. 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. wlcsp-12
22 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201999b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 20, 2013 aat1171 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch data sheet 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. 1.000 1.535 all dimensions in millimeters.

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