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1 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 typical application AAT3218 en in ou t byp gn d on/off 1f 10nf 2. 2f v in gnd gnd v out general description the AAT3218 micropower low dropout linear regulator is ideally suited for portable applications where very fast transient response, extended battery life, and small size are critical. the AAT3218 has been specifically designed for high-speed turn-on and turn-off performance, fast transient response, and good power supply ripple rejec - tion (psrr), and is reasonably low noise, making it ideal for powering sensitive circuits with fast switching require - ments. other features include low quiescent current, typically 70a, and low dropout voltage, typically less than 200mv at the maximum output current level of 150ma. the device is output short-circuit protected and has a thermal shutdown circuit for additional protection under extreme operating conditions. the AAT3218 also features a low-power shutdown mode for extended battery life. a reference bypass pin has been provided to improve psrr performance and output noise, by connecting a small external capacitor from device reference output to ground. the AAT3218 is available in a pb-free, space-saving 5-pin sot23 or 8-pin sc70jw package in 5 factory- programmed voltages: 1.2v, 2.3v, 2.8v, 2.85v, or 3.5v. features? low dropout: 200mv at 150ma ? guaranteed 150ma output ? high accuracy: 1.5% ? 70a quiescent current ? fast line and load transient response ? high-speed device turn-on and shutdown ? high power supply ripple rejection ? low self noise ? short-circuit and over-temperature protection ? uses low equivalent series resistance (esr) ceramic capacitors ? output noise reduction bypass capacitor ? shutdown mode for longer battery life ? low temperature coefficient ? 5 factory-programmed output voltages ? sot23 5-pin or sc70jw 8-pin package applications? bluetooth? headsets ? cellular phones ? digital cameras ? notebook computers ? personal portable electronics ? portable communication devices discontinued downloaded from: http:///
2 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 pin descriptions pin number symbol function sot23-5 sc70jw-8 1 5, 6 in input voltage pin; should be decoupled with 1f or greater capacitor. 2 8 gnd ground connection pin. 3 7 en enable pin; this pin should not be left loating. when pulled low, the pmos pass tr ansis - tor turns off and all internal circuitry enters low -power mode, consuming less than 1a. 4 1 byp bypass capacitor connection; to improve ac ripple rejection, connect a 10nf capacitor to gnd. this will also provide a soft-start function. 5 2, 3, 4 out output pin; should be decoupled with 2.2f ceramic capacitor. pin configuration sot23-5 sc70jw-8 (top view) (top view) gnd out byp en in 12 3 4 5 out out out gnden in in byp 12 3 45 6 7 8 discontinued downloaded from: http:///
3 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at conditions other than the operating conditions specified is not implied. 2. mounted on a demo 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. absolute maximum ratings 1 t a = 25c, unless otherwise noted. symbol description value units v in input voltage 6 v v enin(max) maximum en to input voltage 0.3 i out dc output current p d /(v in -v o ) ma t j operating junction temperature range -40 to 150 c thermal information 2 symbol description rating units q ja maximum thermal resistance (sot23-5, sc70jw-8) 190 c/w p d maximum power dissipation (sot23-5, sc70jw-8) 526 mw recommended operating conditions symbol description rating units v in input voltage 3 (v out +v do ) to 5.5 v t ambient temperature range -40 to +85 c discontinued downloaded from: http:///
4 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 1. v do is defined as v in - v out when v out is 98% of nominal. 2. for v out < 2.3v, v do = 2.5v - v out . electrical characteristics v in = 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 = 2.2f, c in = 1f, t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c. symbol description conditions min typ max units v out output voltage tolerance i out = 1ma to 150ma t a = 25c -1.5 1.5 % t a = -40c to 85c -2.5 2.5 i out output current v out > 1.2v 150 ma v do dropout voltage 1, 2 i out = 150ma 200 300 mv i sc short-circuit current v out < 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 d v out / v out * d v in line regulation v in = v out + 1 to 5.0v 0.09 %/v d v out (line) dynamic line regulation v in = v out + 1v to v out + 2v, i out = 150ma, t r /t f = 2s 2.5 mv d v out (load) dynamic load regulation i out = 1ma to 150ma, t r < 5s 30 t endly enable delay time byp = open 15 s v en(l) enable threshold low 0.6 v v en(h) enable threshold high 1.5 i en leakage current on enable pin v en = 5v 1 a psrr power supply rejection ratio i out = 10ma, c byp = 10nf 1 khz 67 db 10khz 47 1mhz 45 t sd over-temperature shutdown threshold 145 c t hys over-temperature shutdown hysteresis 12 e n output noise noise power bw = 300hz - 50khz 50 vrms tc output voltage temperature coeficient 22 ppm/c discontinued downloaded from: http:///
5 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 typical characteristics unless otherwise noted, v in = 5v, t a = 25c. dropout voltage vs. temperature 0 20 40 60 80 100 120 140 160 180 200 220 240 260 -4 0- 30 -2 0- 10 01 02 030405 06 07 08 09 0 100 110 120 temperature (c) dropout voltage (mv) 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 02 55 07 5 100 125 150 output current (ma) dropout voltage (mv) 85c 25c -40c 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 22 .5 33 .5 44 .5 5 input voltage (v) ground current (a) 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 -4 0- 30 -2 0- 10 01 02 030405 06 07 08 09 0 100 110 120 temperature (c) quiescent current (a) output voltage vs. temperature 1.196 1.197 1.198 1.199 1.200 1.201 1.202 1.203 -4 0- 30 -2 0- 10 01 02 03 0405 06 07 08 09 01 00 temperature (c) output voltage (v) discontinued downloaded from: http:///
6 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 typical characteristics unless otherwise noted, v in = 5v, t a = 25c. over-current protection -200 0 200 400 600 800 1000 1200 time (20ms/div) output current (ma) 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 AAT3218 self noise (c out = 10f, ceramic) 0.001 0.01 0.1 1 10 0.01 0. 11 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. 53 .0 3. 54 .0 4. 55 .0 5.5 input voltage (v) v ih v il discontinued downloaded from: http:///
7 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 functional description the AAT3218 is intended for ldo regulator applications where output current load requirements range from no load to 150ma. the advanced circuit design of the AAT3218 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 AAT3218 is enabled through the implementation of a fast-start con - trol circuit, which accelerates the power-up behavior of fundamental control and feedback circuits within the ldo regulator. fast turn-off response time is achieved by an active out - put pull-down circuit, which is enabled when the ldo regulator is placed in shutdown mode. this active fast shutdown circuit has no adverse effect on normal device operation. the AAT3218 has very fast transient response character - istics, which is an important feature for applications where 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 c bypass values may slow down the ldo regula - tor turn-on time. this ldo regulator has complete short-circuit and ther - mal protection. the integral combination of these two internal protection circuits gives the AAT3218 a compre - hensive 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. functional block diagram error amplifier over-current protection over- temperature protection voltage reference + - in en byp out gnd active feedback control fast- start control discontinued downloaded from: http:///
8 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 applications information to assure the maximum possible performance is obtained from the AAT3218, please refer to the following applica - tion recommendations. input capacitor typically, a 1f or larger capacitor is recommended for c in in most applications. a c in capacitor is not required for basic ldo regulator operation. however, if the AAT3218 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 1f 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 AAT3218 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 1f to 10f. applications utilizing the exceptionally low output noise and optimum power supply ripple rejection characteristics of the AAT3218 should use 2.2f 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 0.47f. bypass capacitor and low noise applications a bypass capacitor pin is provided to enhance the low noise characteristics of the AAT3218 ldo regulator. the bypass capacitor is not necessary for operation of the AAT3218. 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 output 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 data - sheet 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 out - put noise and voltage regulation performance. for this reason, the use of a low leakage, high quality ceramic (npo or c0g type) or film capacitor is highly recom - mended. capacitor characteristics ceramic composition capacitors are highly recommend - ed over all other types of capacitors for use with the AAT3218. 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 impor - tant characteristic to consider when selecting a capaci - tor. esr is the internal series resistance associated with a capacitor that includes lead resistance, internal con - nections, size and area, material composition, and ambi - discontinued downloaded from: http:///
9 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 ent temperature. typically, capacitor 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 0.1f are typically made from npo or c0g materi - als. npo and c0g materials generally have tight toler - ance and are very stable over temperature. larger capacitor values are usually composed of x7r, x5r, z5u, or y5v dielectric materials. large ceramic capacitors (i.e., greater than 2.2f) 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 2.2f y5v capacitor could be reduced to 1f over temperature; this could cause problems 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. capaci tors 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. enable function the AAT3218 features an ldo regulator enable/ disable function. this pin (en) is active high and is com - patible 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 shutdown 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 regulator in a continuously on state. when the ldo regulator is in shutdown mode, an inter - nal 1.5k w resistor is connected between v out and gnd. this is intended to discharge c out when the ldo regula - tor is disabled. the internal 1.5k w has no adverse effect on device turn-on time. short-circuit protection the AAT3218 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 AAT3218 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 AAT3218 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 v out might exceed v in should be avoided since this would forward bias the internal parasitic diode and allow excessive cur - rent flow into the v out pin, possibly damaging the ldo regulator. 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 exceeding 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. discontinued downloaded from: http:///
10 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 thermal considerations and high output current applications the AAT3218 is designed to deliver a continuous output load current of 150ma under normal operating condi - tions. the limiting characteristic for the maximum out - put load current safe operating area is essentially pack - age power dissipation and the internal preset thermal limit of the device. in order to obtain high operating currents, careful device layout and circuit operating con - ditions must be taken into account. the following discussions will assume the ldo regulator is mounted on a printed circuit board utilizing the mini - mum recommended footprint, as stated in the layout considerations section of this datasheet. at any given ambient temperature (t a ), the maximum package power dissipation can be determined by the fol - lowing equation: [t j(max) - t a ] p d(max) = ja constants for the AAT3218 are t j(max) , the maximum junction temperature for the device which is 125c and q ja = 190c/w, the package thermal resistance. typically, maximum conditions are calculated at the maximum operating temperature where t a = 85c, under normal ambient conditions t a = 25c. given t a = 85c, the maximum package power dissipation is 211mw. at t a = 25c, the maximum package power dissipation is 526mw. the maximum continuous output current for the AAT3218 is a function of the package power dissipation and the input-to-output voltage drop across the ldo regulator. refer to the following simple equation: p d(max) i out(max) < (v in - v out ) for example, if v in = 5v, v out = 2.8v, and t a = 25c, i out(max) < 240ma. if the output load current were to exceed 240ma or if the ambient temperature were to increase, the internal die temperature would increase. if the condition remained constant, the ldo regulator thermal protection circuit would activate. to determine the maximum input voltage for a given load current, refer to the following equation. this calcu - lation accounts for the total power dissipation of the ldo regulator, including that caused by ground current. p d(max) = (v in - v out ) i out + v in i gnd this formula can be solved for v in to determine the maximum input voltage. p d(max) + v out i out v in(max) = i out i gnd the following is an example for an AAT3218 set for a 2.3v output: v in(max) = v out = 2.3v i out = 150ma i gnd = 150a v in(max) = 5.8v 526mw + 2.3v ? 150ma 150ma + 150a from the discussion above, p d(max) was determined to equal 526mw at t a = 25c. thus, the AAT3218 can sustain a constant 2.3v output at a 150ma load current as long as v in is 5.8v at an ambient temperature of 25c. 5.8v is the absolute maximum voltage where an AAT3218 would never be operated, thus at 25c, the device would not have any thermal concerns or operational v in(max) limits. this situation can be different at 85c. the following is an example for an AAT3218 set for a 2.3v output at 85c: v in(max) = v out = 2.3v i out = 150ma i gnd = 150a v in(max) = 3.7v 211mw + 2.3v ? 150ma 150ma + 150a discontinued downloaded from: http:///
11 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 from the discussion above, p d(max) was determined to equal 211mw at t a = 85c. higher input-to-output voltage differentials can be obtained with the AAT3218, while maintaining device functions within the thermal safe operating area. to accomplish this, the device thermal resistance must be reduced by increasing the heat sink area or by operating the ldo regulator in a duty-cycled mode. for example, an application requires v in = 4.2v while v out = 2.3v at a 150ma load and t a = 85c. v in is great - er than 3.7v, which is the maximum safe continuous input level for v out = 2.3v at 150ma for t a = 85c. to maintain this high input voltage and output current level, the ldo regulator must be operated in a duty-cycled mode. refer to the following calculation for duty-cycle operation (p d(max) is assumed to be 211mw): %dc = i gnd = 150a i out = 150ma v in = 4.2v v out = 2.3v %dc = 73.87% p d(max) (v in - v out ) ? i out v in ? i gnd %dc = 211m (4.2v - 2.3v) ? 150ma 4.2v ? 150a for a 150ma output current and a 2.5v drop across the AAT3218 at an ambient temperature of 85c, the maxi - mum on-time duty cycle for the device would be 73.87%. high peak output current applications some applications require the ldo regulator to operate at continuous nominal level with short duration, high- current peaks. the duty cycles for both output current levels must be taken into account. to do so, first calcu - late the power dissipation at the nominal continuous level, then factor in the additional power dissipation due to the short duration, high-current peaks. for example, a 2.3v system using an AAT3218igv- 2.3-t1 operates at a continuous 100ma load current level and has short 150ma current peaks. the current peak occurs for 378s out of a 4.61ms period. it will be assumed the input voltage is 4.2v. first, the current duty cycle in percent must be calcu - lated: % peak duty cycle: x/100 = 378s/4.61ms % peak duty cycle = 8.2% the ldo regulator will be under the 100ma load for 91.8% of the 4.61ms period and have 150ma peaks occurring for 8.2% of the time. next, the continuous nominal power dissipation for the 100ma load should be determined then multiplied by the duty cycle to conclude the actual power dissipation over time. p d(max) = (v in - v out ) i out + v in i gnd p d(100ma) = (4.2v - 2.3v) 100ma + 4.2v 150a p d(100ma) = 190.6mw p d(91.8%d/c) = %dc p d(100ma) p d(91.8%d/c) = 0.918 x 190.6mw p d(91.8%d/c) = 175mw the power dissipation for a 100ma load occurring for 91.8% of the duty cycle will be 175mw. now the power dissipation for the remaining 8.2% of the duty cycle at the 150ma load can be calculated: p d(max) = (v in - v out ) i out + v in i gnd p d(150ma) = (4.2v - 2.3v) 150ma + 4.2v 150ma p d(150ma) = 285.6mw p d(8.2%d/c) = %dc x p d(150ma) p d(8.2%d/c) = 0.082 x 285.6mw p d(8.2%d/c) = 23.4mw the power dissipation for a 150ma load occurring for 8.2% of the duty cycle will be 23.4mw. finally, the two power dissipation levels can summed to determine the total true power dissipation under the varied load: p d(total) = p d(100ma) + p d(150ma) p d(total) = 175mw + 23.4mw p d(total) = 198.4mw the maximum power dissipation for the AAT3218 oper - ating at an ambient temperature of 85c is 211mw. the device in this example will have a total power dissipation of 198.4mw. this is well within the thermal limits for safe operation of the device. discontinued downloaded from: http:///
12 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 printed circuit board layout recommendations in order to obtain the maximum performance from the AAT3218 ldo regulator, careful consideration should be given to the printed circuit board (pcb) layout. if grounding connections are not properly made, power supply ripple rejection, low output self noise, and tran - sient response can be compromised. figure 1 shows a common ldo regulator layout scheme. the ldo regulator, external capacitors (c in , c out , and c byp ), and the load circuit are all connected to a common ground plane. this type of layout will work in simple applications where good power supply ripple rejection and low self noise are not a design concern. for high- performance applications, this method is not recom - mended. the problem with the layout in figure 1 is the bypass capacitor and output capacitor share the same ground path to the ldo regulator ground pin, along with the high-current return path from the load back to the power supply. the bypass capacitor node is connected directly to the ldo regulator internal reference, making this node very sensitive to noise or ripple. the internal refer - ence output is fed into the error amplifier, thus any noise or ripple from the bypass capacitor will be subsequently amplified by the gain of the error amplifier. this effect can increase noise seen on the ldo regulator output, as well as reduce the maximum possible power supply rip - ple rejection. there is pcb trace impedance between the bypass capacitor connection to ground and the ldo regulator ground connection. when the high load current returns through this path, a small ripple voltage is cre - ated, feeding into the c byp loop. figure 2 shows the preferred method for the bypass and output capacitor connections. for low output noise and highest possible power supply ripple rejection perfor - mance, it is critical to connect the bypass and output capacitor directly to the ldo regulator ground pin. this method will eliminate any load noise or ripple current feedback through the ldo regulator. evaluation board layout the AAT3218 evaluation layout follows the recommend printed circuit board layout procedures and can be used as an example for good application layouts. note: board layout is not shown to scale. ldo regulator c byp c out r trace r trace r trace r trace c in r load vin en gnd vout byp i load i ripple i in v in gnd dc input i gnd c byp gnd loop i load return + noise and ripple i byp + noise figure 1: common ldo regulator layout with c byp ripple feedback loop. discontinued downloaded from: http:///
13 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 ldo regulator c byp c out r trace r trace r trace r trace c in r load vin en gnd vout byp v in gnd i in i load i gnd i ripple dc input i load return + noise and ripple i byp only figure 2: recommended ldo regulator layout. figure 3: evaluation board figure 4: evaluation board component side layout. solder side layout. figure 5: evaluation board top side silk screen layout / assembly drawing. discontinued downloaded from: http:///
14 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 ordering information output voltage package marking 1 part number (tape and reel) 2 1.2v sot23-5 kwxyy AAT3218igv-1.2-t1 2.3v AAT3218igv-2.3-t1 2.8v emxyy AAT3218igv-2.8-t1 2.85v hoxyy AAT3218igv-2.85-t1 3.5v AAT3218igv-3.5-t1 1.2v sc70jw-8 kwxyy AAT3218ijs-1.2-t1 2.3v AAT3218ijs-2.3-t1 3.5v AAT3218ijs-3.5-t1 skyworks green? products are compliant with all applicable legislation and are halogen-free. for additional information, refer to skyworks de?nition of green? , document number sq04-0074. package information sot23-5 4 4 0.15 0.07 0.45 0.15 0.10 bsc 1.20 0.25 1.575 0.125 2.80 0.20 0.40 0.10 0.60 ref 2.85 0.15 1.90 bsc 0.95bsc 1.10 0.20 10 5 gauge plane 0.075 0.075 0.60 ref all dimensions in millimeters. 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . discontinued downloaded from: http:///
15 AAT3218 da ta sheet 150ma micropower tm high performance ldo skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202249a ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 7, 2012 copyright ? 2012 skyworks solutions, inc. all rights reserved. information in this document is provided in connection with skyworks solutions, inc. (skyworks) pr oducts or services. these materials, including the information contained herein, are provided by sky works as a service to its customers and may be used for informational purposes only by the customer. skyworks a ssumes no responsibility for errors or omissions in these materials or the information contained her ein. sky- works may change its documentation, products, services, speciications or product descriptions at any time, without notice. skyworks makes no commitment to update the materials or information and shall have no responsibility whatsoever for conlicts, incompatibilities, or other dificulties arising from any fut ure changes. no license, whether express, implied, by estoppel or otherwise, is granted to any intellectual prope rty rights by this document. skyworks assumes no liability for any materials, products or informatio n provided here- under, including the sale, distribution, reproduction or use of skyworks products, information or ma terials, except as may be provided in skyworks terms and conditions of sale. the materials, products and information are provided as is without warranty of any kind, whether e xpress, implied, statutory, or otherwise, including fitness for a particular purpose or use, merchantability, performance, quality or non-infringement of any intellectual proper ty right; all such warranties are hereby expressly disclaimed. skyworks does not warrant the accuracy or completeness of the information, text, graphics or other items contained within these materials. skyworks shall not be liable for any damages, in- cluding but not limited to any special, indirect, incidental, statutory, or consequential damages, i ncluding 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, o r 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 applicatio ns 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 dev iate from published speciications as a result of design defects, errors, or operation of products ou tside of pub- lished parameters or design speciications. customers should include design and operating safeguards to minimize these and other risks. skyworks assumes no liability for applications assistance, custom er product design, or damage to any equipment resulting from the use of skyworks products outside of stated pub lished speciications 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 identiication purposes only, and are the property of their respective owners. additional information , including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by refere nce. sc70jw-8 0.225 0.075 0.45 0.10 0.05 0.05 2.10 0.30 2.00 0.20 7 3 4 4 1.75 0.10 0.85 0.15 0.15 0.05 1.10 max 0.100 2.20 0.20 0.048ref 0.50 bsc 0.50 bsc 0.50 bsc all dimensions in millimeters. discontinued downloaded from: http:///

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