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AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 1 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksin c. com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 general description the AAT2608A is a member of skyworks' total power management ic (tpmic tm ) product family. it contains a fully integrated step-down converter and eight low drop - out (ldo) regulators, making it ideal for general multiple rails applications. the step-down converter is a 800ma synchronous con - verter which operates at a switching frequency of 1.5mhz, minimizing the size of external components while keeping efficiency greater than 90%. the step-down converter is capable of 1a of peak current and has an integrated com - pensation network. the input voltage range is 2.7v to 5.5v, and the output can be externally adjusted from 0.6v to 80% of the step-down converter's input voltage. it includes an independent enable to provide a convenient solution to implement any power up or power down sequencing. the AAT2608A has eight high-psrr ldos which provides noise immunity to the generated power rails. the ldos have independent enable pins to meet any power-up or power-down sequencing requirements. each ldo requires a small output ceramic capacitor for stability. 5 of the ldos have a fixed output which is programmed during manufacturing; 3 ldos have adjustable outputs pro - grammable with external resistors. ldos 1, 2, 3 and 4 share the same input voltage as the step-down con - verters control circuitry. ldo5 shares its input with ldo6; ldo7 shares its input with ldo8. the AAT2608A is available in the small 28-pin 4mm x 4mm tqfn package. features? 1.5mhz step-down converter ? 800ma, externally adjustable ? synchronous with integrated switches ? independent enable ? independent input power and ground ? operating input voltage range of 2.7v to 5.5v ? ldo1, ldo2, ldo3 and ldo4 regulators share same input as the step-down converter ? ldo5 and ldo6 are tied to the same input ? ldo7 and ldo8 are tied to the same input ? ldo1, ldo7 and ldo8 have adjustable outputs with external resistors ? ldo2, ldo3, ldo4, ldo5 and ldo6 have factory programmed outputs ? all ldos have: ? independent enable ? 300ma current capability ? high psrr (68db @10khz) ? low ground current (30a) ? over-current protection ? over-temperature protection ? operating input voltage range from 2.7v to 5.5v ? tqfn44-28 package applications? cellular application ? handheld products ? media players (mp4 players) ? portable navigation devices (pnd) downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 2 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 typical application AAT2608A vinbuck vcc fbbuck ldo1ldo2 ldo3 ldo4 ldo5 ldo6 ldo7 ldo8 enbuck enld1enld2 enld3 enld4 enld5 enld6 enld7 enld8 pgnd p a a v ldo8 p a a a a a a a a fbldo1 a a v ldo1 v ldo7 v ldo8 c ldo8 1f v ldo7 c ldo7 1f v ldo6 c ldo6 1f v ldo5 c ldo5 1f v ldo4 c ldo4 1f v ldo3 c ldo3 1f v ldo2 c ldo2 1f v ldo1 v buck c ldo1 1f c buck 22f c inbuck 10f l12.2h r ldo1 r ldo1 r ldo7 r ldo7 r buck r buck r ldo8 r ldo8 c vcc 2.2fc vin56 2.2fc vin78 2.2f vin56 a vin78 a fbldo7 a fbldo8 a 2.7v to 5.5v 2.7v to 5.5v agnd p lx downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 3 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 pin descriptions pin # symbol function 1 enld3 ldo3 enable; active high. 2 enld2 ldo2 enable; active high. 3 enld1 ldo1 enable; active high. 4 agnd analog ground. 5 vcc input to power control circuit for step-down converter, ldo1, ldo2, ldo3 and ldo4. 6 ldo1 ldo1 output voltage. 7 fbldo1 feedback pin for ldo1 8 ldo2 ldo2 output voltage. 9 ldo3 ldo3 output voltage. 10 ldo4 ldo4 output voltage. 11 ldo5 ldo5 output voltage. 12 ldo6 ldo6 output voltage. 13 ldo7 ldo7 output voltage. 14 fbldo7 feedback pin of ldo7. 15 fbldo8 feedback pin of ldo8. 16 ldo8 ldo8 output voltage. 17 vin78 input to ldo7 and ldo8. 18 vin56 input to ldo5 and ldo6. 19 enld8 ldo8 enable; active high. 20 enld7 ldo7 enable; active high. 21 enld6 ldo6 enable; active high. 22 vinbuck power input to the step-down converter input. 23 lx switching node for step-down converter regulator. 24 pgnd power ground for step-down converter regulator. 25 enld5 ldo5 enable; active high. 26 enld4 ldo4 enable; active high. 27 enbuck enable for step-down converter; active high. 28 fbbuck feedback input for step-down converter regulator. pin configuration tqfn44-28 (top view) 12 3 4 5 6 7 89 10 28 27 26 25 24 23 22 11 12 13 14 2120 19 18 17 16 15 enld3 enld2enld1 agnd vcc ldo1 fbldo1 ldo2 ldo3 ldo4 ldo5 ldo6 ldo7 fbldo7 vin56 enld8vin78 ldo8 fbldo8 enld7 enld6 lx vinbuck pgnd enld5 enld4 enbuck fbbuck downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 4 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 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. only one absolute maximum rating should be applied at any one time. 2. mounted on an fr4 board. absolute maximum ratings 1 symbol description value units vin, vcc, vin5/6, vin7/8, enbk1, enld1, enld2, enld3, enld4, enld5, enld6, enld7, enld8, fbld1, fbld7 and fbld8, fb to gnd -0.3 to 6.5 v lx to pgnd -0.3 to v vin + 0.3 v vout1, vout2, vout3, vout4 to gnd -0.3 to v vcc + 0.3 v vout5, vout6 to gnd -0.3 to v vin5/6 + 0.3 vout7, vout8 to gnd -0.3 to v vin7/8 + 0.3 v pgnd to gnd -0.3 to +0.3 thermal information 2 symbol description value units ja thermal resistance 50 c/w p d maximum power dissipation 2 w t j operating temperature range -40 to 150 c t s storage temperature range -65 to 150 t lead maximum soldering temperature (at leads, 10 sec) 300 downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 5 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 1. specification over the -40c to +85c operating temperature range is assured by design, characterization and correlation with statistical process controls. electrical characteristics 1 v cc = v in = v in56 = v in78 = v inldo = 5.0v, -40c t a +85c, unless otherwise noted. typical values are t a = 25c. symbol description conditions min typ max units logic control / protection v enldx v enbuck input high threshold 1.4 v input low threshold 0.3 v step-down regulator v inbuck , v cc input voltage range 2.7 5.5 v i q quiescent current i out = 0ma, device switching, all ldos disabled 70 a i sd shutdown current enbk1 = gnd 1 a v o_step-down output voltage programmable range using external feedback resistors 0.6 80% of v in v v reg output voltage accuracy 0c t a 85c -3 +3 % i lim p-channel current limit 1000 ma t startup startup time from device enable to 90% of nominal output voltage 100 s t ramp ramp-up time time to ramp output voltage from 10% to 90% 60 s r ds(on)h high-side switch on-resistance 260 m r ds(on)l low-side switch on-resistance 220 m v out / (v out v in ) line regulation 0.2 %/v f osc oscillator frequency 1.5 mhz uvlo under-voltage lockout threshold falling 2 v rising 2.2 low-dropout regulators (ldo1-ldo8) v inldo input voltage range 2.7 5.5 v v outx ldo output voltage i ldo = 1ma to 300ma, otp per requirement 0.6 v inldo - v do v ldo accuracy i ldo = 10ma -3 +3 % i q ldo quiescent current v inldo = 5v, added quiescent current when ldo is enabled 30 55 a line regulation i ldo = 10ma 0.1 %/v load regulation i ldo = 1ma to 300ma 0.003 %/ma psrr v inx = 5v, v ox = 1.8v, en = high, f = 10khz, i ldo = 100ma 68 db v do dropout voltage i ldo = 250ma 250 500 mv i ldo(lim) ldo current limit 300 ma thermal t sd over-temperature shutdown threshold rising 145 c t hys over-temperature shutdown hysteresis 25 c downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 6 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 programming output voltages via otp programmable output voltage range resolution step-down1 0.6v 80% of v in externally adjustable with 0.6v internal reference ldo1 0.6v externally adjustable with 0.6v internal reference ldo2 0.6v 3.7v 100mv per otp bit ldo3 0.6v 3.7v 100mv per otp bit ldo4 0.6v 3.7v 100mv per otp bit ldo5 0.6v 3.7v 100mv per otp bit ldo6 0.6v 3.7v 100mv per otp bit ldo7 0.6v externally adjustable with 0.6v internal reference ldo8 0.6v externally adjustable with 0.6v internal reference downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 7 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 typical characteristics?step-down (buck) converter input current vs. input voltage (buck v out = 1.2v; switching; all ldos disabled) input voltage (v) input current (a) 2. 73 .1 3. 53 .9 4. 34 .7 5. 15 .5 30 40 50 60 70 80 90 100 efficiency vs. output current (buck v out = 1.8v) output current (ma) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 1 0. 11 0 100 1000 v in = 2.7v v in = 3.6v v in = 4.2v v in = 5.5v load regulation (buck v out = 1.2v; c out = 22f) output current (ma) load regulation (% ) 1 0. 11 0 100 1000 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 v in = 2.7v v in = 3.6v v in = 4.2v v in = 5.5v load transient (buck v out = 1.2v; v in = 3.6v; i out = 80ma to 800ma) time (100s/div) output voltage (50mv/div) (top) output current (500ma/div) (bottom) 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 line regulation (buck v out = 1.2v) input voltage (v) line regulation (%) 2. 73 .1 3. 53 .9 4. 34 .7 5. 15 .5 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 i out = 1ma i out = 10ma i out = 200ma i out = 400ma i out = 800ma soft start (buck v out = 1.2v; v in = 3.6v; i out = 100ma) time (100s/div) enable voltage (top) (1v/div) output voltage (middle) (1v/div) input current (bottom) (100ma/div) -3 -2 -1 0 1 2 3 4 5 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 8 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 typical characteristics?ldo1-ldo8 input current vs. input voltage (contributed by each ldo) input voltage (v) input current (a) 2. 73 .1 3. 53 .9 4. 34 .7 5. 15 .5 20 22 24 26 28 30 32 34 36 38 40 load regulation (ldo1 v out = 1.85v) output current (ma) load regulation (% ) 1 0. 11 0 100 1000 -0.10 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 v in = 2.7v v in = 3.6v v in = 4.2v v in = 5.5v load regulation (ldo2 v out = 2.6v) output current (ma) load regulation (% ) 1 0. 11 0 100 1000 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 v in = 3.0v v in = 3.6v v in = 4.2v v in = 5.5v line regulation (ldo1 v out = 1.85v) input voltage (v) line regulation (%) 2. 73 .1 3. 53 .9 4. 34 .7 5. 15 .5 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 i out = 1ma i out = 100ma i out = 150ma i out = 250ma i out = 300ma line regulation (ldo2 v out = 2.6v) input voltage (v) line regulation (%) 2. 73 .1 3. 53 .9 4. 34 .7 5. 15 .5 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 i out = 1ma i out = 100ma i out = 150ma i out = 250ma i out = 300ma downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 9 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 typical characteristics?ldo1-ldo8 (continued) output voltage error vs. temperature (ldo1 v out = 1.85v; v in = 3.6v) temperature (c ) output voltage error (%) 75 50 25 0 -25 -50 100 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 i out = 1ma i out = 250ma output voltage error vs. temperature (ldo2 v out = 2.6v; v in = 3.6v) temperature (c ) output voltage error (%) 75 50 25 0 -25 -50 100 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 i out = 1ma i out = 250ma load transient (ldo1 v out = 1.85v; v in = 3.6v; i out = 30ma to 300ma) time (200s/div) output voltage (50mv/div) (top) output current (200ma/div) (bottom) 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 load transient (ldo2 v out = 2.6v; v in = 3.6v; i out = 30ma to 300ma) time (200s/div) output voltage (20mv/div) (top) output current (200ma/div) (bottom) 2.50 2.52 2.54 2.56 2.58 2.60 2.62 2.64 2.66 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 power supply rejection ratio (psrr) (v in(dc) = 5v; v out = 1.85v; i out = 100ma) frequency (hz) psrr (db) 0 10 20 30 40 50 60 70 80 1000000 100000 10000 1000 100 10 downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 10 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 functional description the AAT2608A is a highly integrated voltage regulating power management unit for mobile handsets or other portable devices. it includes a 800ma switch-mode step- down converter and eight low-noise, high-psrr low- dropout (ldo) regulators. it operates from an input voltage between 2.7v and 5.5v making it ideal for lithi - um-ion or 5v regulated power sources. all nine convert - ers have separate enable pins for ease of use. synchronous step- down (buck) converter the AAT2608A switch-mode step-down converter is a constant frequency peak current mode pwm converter with internal compensation. the input voltage range is 2.7v to 5.5v. the output voltage range is 0.6v to 80% of v in . the high 1.5mhz switching frequency allows the use of small external inductor and capacitor. functional block diagram 1. 5 mhz oscillator soft start sawtooth generator feedback otp vre f1 compensation control logic lx fbbuck vinbuck pgnd uvlo bias vcc enbuck vcc n p p s s otp vre f4 s s vcc bias enld8 vin78 ldo8 otp vre f4 s s bias vcc ldo1 enld1 vcc thermal shutdown error amp pwm comparator downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 11 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 the step-down converter offers soft-start to limit the current surge seen at the input and eliminate output voltage overshoot. the current across the internal p-channel power switch is sensed and turns off when the current exceeds the current limit. also, thermal protec - tion completely disables switching if internal dissipation becomes excessive, thus protecting the device from damage. the junction over-temperature threshold is 145c with 25c of hysteresis. the buck converter is designed for a peak continuous output current of 800ma. it was designed to maintain over 80 % efficiency at its maximum rated output cur - rent load of 800ma with a 1.2v output. peak efficiency is above 90 %. it also has excellent transient response, load and line regulation. transient response time is typically less than 60ns. ldo regulators the AAT2608A includes eight ldo regulators. the regu - lators operate from the 2.7v to 5.5v input voltage to a regulated output voltage. each ldo regulator has its own independent enable pin. ldo regulators 1, 7 and 8 have adjustable output voltages set by resistors. ldo regulators 2 thru 6 have a fixed output programmed during manufacturing. each ldo consumes 30a of qui - escent current and is stable with a small 1.0f ceramic output capacitor. these ldos offer high power supply rejection, over-current protection and over-temperature protection . feedback resistor selection the output voltage of the buck converter and ldos 1, 7 and 8 is each set with an individual resistor divider feed - back network. the voltage output of the buck converter can be set between 0.6v and 80% of v in . the voltage output of the ldos can be set between 0.6v and v in - v do . v out is defined by the following equation: v ou t = 0.6v 1 + r1 r2 to minimize the current consumed by the voltage divid - er and to isolate the fb pin from noise, the resistor val - ues for r1 and r2 should be beween 5k and 500k. application information synchronous step- down (buck) converter 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. table 1 displays suggested inductor values for various output voltages. manufacturers 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. input capacitor select a 4.7f to 10f x7r or x5r ceramic capacitor for the input; see table 3 for suggested capacitor compo - nents. to estimate the required input capacitor size, determine the acceptable input ripple level (v pp ) and solve for c in . the calculated value varies with input voltage and is a maximum when v cc 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 coef - ficient characteristics when selecting the proper value. for example, the capacitance of a 10f, 6.3v, x5r ceramic capacitor with 5.0v dc applied is actually about 6f. downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 12 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 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 12 for v in = 2 * v o i o rm s 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 o is twice v cc . 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 AAT2608A step-down switching regulators. 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. 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 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 should be placed in parallel with the low esr, esl bypass ceramic. 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 10f to 22f 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; see table 2 for suggested capacitor components the output voltage droop due to a load transient is dominated 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 several switching cycles, the loop responds and the inductor current increases to match the load current demand. the relationship of the output voltage droop during the several 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 10f. 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. the maximum output capacitor rms ripple current is given by: 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. downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 13 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 ldo regulatorsinput capacitor typically, a 1.0f or larger ceramic capacitor is recom - mended for c vcc , c in5/6 , and c in7/8 in most applications. the input capacitor should be located as close to the input (vcc/vin5/6/vin7/8) of the device as practically possible. c vcc , c in5/6 , and c in7/8 values greater than 1.0f will offer superior input line transient response and will assist in maximizing power supply ripple rejection. output capacitor for proper load voltage regulation and operational sta - bility, a capacitor is required between the ldox and agnd pins. the c outx capacitor connection to the ldo regulator ground pin should be made as direct as prac - tically possible for maximum device performance. the AAT2608A's ldo regulators have been specifically designed to function with very low esr ceramic capaci - tors. although the device is intended to operate with these low esr capacitors, it is stable over a very wide range of capacitor esr, thus it will also work with higher esr tantalum or aluminum electrolytic capacitors. however, for best performance, ceramic capacitors are recommended. typical output capacitor values for maximum output cur - rent conditions range from 1f to 10f. thermal calculations there are three types of losses associated with the AAT2608A total power management solution (one step - down converter and eight ldo regulators): switching losses, conduction losses, and quiescent current losses. conduction losses are associated with the r ds(on) charac - teristics of the internal power switches/fets of both of the stepdown regulators and the power loss associated with the voltage difference across the pass switch/fet of the four ldo regulators. switching losses are dominated by the gate charge of the power output switching devic - es. at full load, assuming continuous conduction mode (ccm), a simplified form of the losses is given by the following (quiescent and switching losses are ignored, since conduction losses are so dominant): p b i ob 2 (r ds(on)h v ob + r ds(on)l [v inb1 - v ob1 ]) v in = p ldo1 = i ldo1 (v cc - v ol1 ) p ldo2 = i ldo2 (v cc - v ol2 ) p ldo3 = i ldo3 (v cc - v ol3 ) p ldo4 = i ldo4 (v cc - v ol4 ) p ldo5 = i ldo5 (v in5/6 - v ol5 ) p ldo6 = i ldo6 (v in5/6 - v ol6 ) p ldo7 = i ldo7 (v in7/8 - v ol7 ) p ldo8 = i ldo8 (v in7/8 - v ol8 ) p ldo8 = i ldo8 (v in7/8 - v ol8 ) p total = p b + p ldo1 + p ldo2 + p ldo3 + p ldo4 + p ldo5 + p ldo6 + p ldo7 + p ll p b : power dissipation of the dc-dc regulator i ob : output current of the specific dc-dc regulator r ds(on)h : resistance of the internal high-side switch/fet r ds(on)l : resistance of the internal low-side switch/fet v ob : output voltage of the dc-dc regulator v cc : input voltage of the dc-dc regulator and ldos 1 to 4 p ldox : power dissipation of the specific ldo regulator i ldox : output current of the specific ldo regulator v in5/6 : input voltage of regulators ldo5 and ldo6 v in7/8 : input voltage of regulators ldo7 and ldo8 v olx : output voltage of the specific ldo regulator p total : total power dissipation of the AAT2608A since r ds(on) and conduction losses all vary with input voltage, the dominant losses should be investigated over the complete input voltage range. given the total con - duction losses, the maximum junction temperature (125c) can be derived from the ja for the tqfn44-28 package which is 50c/w. t j(max) = p total ja + t a t j(max) = p total ja + ta t j(max) : maximum junction temperature p total : total conduction losses ja : thermal impedance of the package t a : ambient temperature downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 14 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 layout the suggested pcb layout for the AAT2608A is shown in figures 4 and 5. the following guidelines should be used to help ensure a proper layout. 1. the input capacitors (c1, c2, c3, c4) should con - nect as closely as possible to vin (pin 22), vin56 (pin 18), vin78 (pin 17), and vcc (pin 5), and agnd/pgnd (pins 4 and 24). 2. c13 (the step-down regulator output capacitor) and l1 should be connected as closely as possible. the connection of l1 to the lx pin should be as short as possible. 3. the feedback trace or fbx pin (pins 7, 14, 15, and 28) should be separate from any power trace and connect as closely as possible to the load point. sensing along a high current load trace will degrade dc load regulation. if external feedback resistors are used, they should be placed as closely as possible to the fbx pin (pins 7, 14, 15, and 23) to minimize the length of the high impedance feedback trace. 4. the resistance of the trace from the load return to the pgnd (pins 24) should be kept to a minimum. this will help to minimize any error in dc regulation due to differences 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 tqfn44-28 exposed paddle to the ground plane. manufacturer part number/ type inductance (h) rated current (a) dcr (m) (max) size (mm) lxwxh tdk ltf5022 1.2 4.3 25 5x5.2x2.2 1.8 3.6 32 2.2 3.2 40 3.3 2.5 60 wurth electronik we-tpc type m 1 2.6 30 4.8x4.8x1.8 1.8 2.35 50 2.7 2.03 60 3.3 1.8 65 we-tpc type mh 1.2 2.8 20 4.8x4.8x2.8 1.8 2.45 25 2.2 2.35 28 2.7 1.95 30 3.3 1.8 35 murata lqh55d 1 4 19 (typ) 5x5.7x4.7 1.5 3.7 22 (typ) 2.2 3.2 29 (typ) 3.3 2.9 36 (typ) table 1: suggested inductor components. manufacturer part number value voltage temp. co. case avx 0603zd105k 1f 10 x5r 0603 0603zd225k 2.2f 10 tdk c1608x5r1e105k 1f 25 x5r 0603 c1608x5r1c225k 2.2f 16 c1608x5r1a475k 4.7f 10 c2012x5r1a106k 10f 10 0805 c3216x5r1a226k 22f 10 1206 murata grm188r61c105k 1f 16 x5r 0603 grm188r61a225k 2.2f 10 grm219r61a106k 10f 10 0805 grm31cr71a226k 22f 10 x7r 1206 taiyo yuden lmk107bj475ka 4.7f 10 x5r 0603 table 2: suggested capacitor components. downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 15 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 l1 2.2h r14 r15 v cc c42.2f c2 2.2f c110f c51f c61f c71f c81f c13 22f c3 2.2f c12 1f c11 1f c10 1f c91f r81m r71m r61m r51m r4 1m r31m aat2608_qfn44-28 vcc r21m r11m enable tb1 vin vin r17100k r16100k ldo1 ldo1 r13100k r12100k ldo7 ldo7 r11100k r10100k ldo8 ldo8 tp2 v in tp1 v cc tp3 vin56 tp4 vin78 tp5ldo8 tp12ldo1 tp11ldo2 tp10ldo3 tp9ldo4 tp8ldo5 tp7ldo6 tp6ldo7 tp13v out_buck c14 jp1 enbuck 27 vcc 5 enld1 3 enld2 2 vin56 18 enld3 1 ldo3 9 pgnd 24 fbldo1 7 fbbuck 28 lx 23 vinbuck 22 enld4 26 enld5 25 vin78 17 ldo7 13 ldo6 12 ldo5 11 ldo4 10 enld6 21 fbldo8 15 enld7 20 enld8 19 ldo2 8 agnd 4 ldo1 6 fbldo7 14 ldo8 16 u1 AAT2608A 1 16 sw1 figure 1: AAT2608A evaluation board schematic. figure 2: AAT2608A evaluation board figure 3: AAT2608A evaluation board top side pcb layout. bottom side pcb layout. downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 16 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 2012 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. ordering information package marking 1 part number (tape and reel) 2 tqfn44-28 9rxyy AAT2608Ainj-1-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 3 tqfn44-28 4.000 0.050 4.000 0.050 pin 1 dot by marking top view 2.600 0.050 2.600 0.050 bottom view detail "" 0.50 0.050 0.050 0.050 0.20 ie view 0.400 0.050 0.20 0.050 0.40 0.050 pin 1 niator detail "" 0. all dimensions in millimeters. downloaded from: http:///
AAT2608A da ta sheet eight-channel ldo with dc/dc con ve rt er 17 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202207a ? skyworks proprietary information ? products and product information are subject to change without notice. ? july 25, 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. downloaded from: http:///

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