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PAM2306 dual high-efficiency pwm step-down dc-dc coverter 1 , power analog microelectronics inc www.poweranalog.com 07/2008 rev 1.0 features applications general description efficiency up to 96% only 40a (typ. per channel) quiescent current output current: up to 1a per channel internal synchronous rectifier 1.5mhz switching frequency soft start under-voltage lockout short circuit protection thermal shutdown small 12l wdfn3x3 package rohs compliant cellular phone portable electronics personal information appliances wireless and dsl modems mp3 players the PAM2306 is a dual step-down current-mode, dc-dc converter. at heavy load, the constant- frequency pwm control performs excellent stability and transient response. to ensure the longest battery life in portable applications, the PAM2306 provides a power-saving pulse- skipping modulation (psm) mode to reduce quiescent current under light load operation. the PAM2306 supports a range of input voltages from 2.5v to 5.5v, allowing the use of a single li+/li-polymer cell, multiple alkaline/nimh cell, usb, and other standard power sources. the dual output voltages are available for 3.3v, 2.8v, 2.5v, 1.8v, 1.5v, 1.2v or adjustable. all versions employ internal power switch and synchronous rectifier for to minimize external part count and realize high efficiency. during shutdown, the input is disconnected from the output and the shutdown current is less than 0.1 a. other key features include under-voltage lockout to prevent deep battery discharge. pb-free package and typical application ( ) rx2 rx1 1 v v ref outx + = en2 nc2 fb2 vin2 lx2 fb1 PAM2306 1 2 49 10 11 gnd lx1 gnd 8 5 nc1 3 12 v out2 l2 10 f c in2 100pf vin1 7 6 en1 v in1 4 . 7f l1 r22 47f v out1 100 pf 10 f r12 v in2 c fw1 c out1 c in1 c out2 c fw2 r11 r21 figure 1. adjustable voltage regulator
en2 nc2 fb2 vin2 lx2 fb1 PAM2306 1 2 49 10 11 gnd lx1 gnd 8 5 nc1 12 v out2 l2 c in2 10 f vin1 7 6 en1 v in1 4 . 7f l1 4 . 7f v out1 10 f v in2 c out1 c in1 c out2 3 v outx = 1 . 2v , 1 . 5v , 1 . 8v , 2 . 5v, 2.8v or 3 . 3v figure 2. fixed voltage regulator typical application PAM2306 dual high-efficiency pwm step-down dc-dc coverter 2 , power analog microelectronics inc www.poweranalog.com 07/2008 rev 1.0 block diagram ex n r1 r2 fx b -++ - + + pwm comp + - iamp + - ircmp lx x gnd synchronous rectifier nch () main switch pch () vinx comp vin shutdown osc rs latch 0 6vref . freq shift - + ea sq rq switching logic and blanking circuit slope comp 15m osc . anti shoot thru - -
pin no . pin name pin function 1 vin2 power input of channel 2 . 2 lx2 pin for switching of channel 2 . 3 , 9 , exposed pad gnd ground . the exposed pad must be soldered to a large pcb and connected to gnd for maximum power dissipation . 4 fb1 feedback of channel 1 . 5 , 11 nc1 , nc2 no connection 6 en1 chip enable of channel 1 ( active high ). v en1 v in1 . 7 vin1 power input of channel 1 . 8 lx1 pin for switching of channel 1 . 10 fb2 feedback of channel 2 . 12 en2 chip enable of channel 2 ( active high ). v en2 v in2 . PAM2306 dual high-efficiency pwm step-down dc-dc coverter 3 , power analog microelectronics inc www.poweranalog.com 07/2008 rev 1.0 pin configuration and marking information top view wdfn - 12l 3x3 v: v : output voltage 2 (refer to ?ordering information?) x: internal code y: year w: week 1 2 output voltage 1 vin2 lx2 n1 c f1 b e2 n n2 c f2 b l1 x gnd gnd e1 n vin1 11 10 9 1 2 3 4 5 12 67 8 gnd 2306v v xxxyw 12 (exposed pad)
PAM2306 dual high-efficiency pwm step-down dc-dc coverter 4 , power analog microelectronics inc www.poweranalog.com 07/2008 rev 1.0 absolute maximum ratings these are stress ratings only and functional operation is not implied exposure to absolute maximum ratings for prolonged time periods may affect device reliability all voltages are with respect to ground . . . input voltage................................. 0.3v to 6.5v en1, fb1, lx1, en2, fb2 and lx2 pin voltage........ - -. ( +. ) - 03vto v 03v junction temperature................................150c storage temperature range....... 65c to 150c soldering temperature.....................260c 10sec in , recommended operating conditions supply voltage...............................2.5v to 5.5v c c junction temperature range.........-40c c ambient temperature range......... 40 to 85 to 125 - thermal information parameter symbol package maximum unit thermal resistance (junction to ambient) ja wdfn 3x3-12 60 c/w thermal resistance (junction to case) jc wdfn 3x3-12 8.5 c/w power dissipation p d wdfn 3x3-12 1.66 w
PAM2306 dual high-efficiency pwm step-down dc-dc coverter 5 , power analog microelectronics inc www.poweranalog.com 07/2008 rev 1.0 electrical characteristic t =25 c, v =3.6v, v =1.8v, c =10f, c =10f, l=2.2h, unless otherwise noted. ainoino o parameter symbol test conditions min typ max units input voltage range v in 2.5 5.5 v regulated feedback voltage v fb 0.588 0.6 0.612 v reference voltage line regulation v fb 0.3 %/v r egulated output voltage accuary v o i o =100ma -3 +3 % peak inductor current i pk v in =3v,v fb =0.5vorv o =90% 1.5 a output voltage line regulation lnr v in =2.5vto5v,i o =10ma 0.2 0.5 %/v output voltage load regulation ldr i o =1ma to 1a 0.5 1.5 % quiescent current (per channel) i q no load 40 70 a shutdown current (per channel) i sd v en =0v 0.1 1 a v o = 100% 1.2 1.5 1.8 mhz oscillator frequency f os c v fb =0vorv o =0v 500 khz p mosfet 0.3 0.45 drain-source on-state resistance r ds(on) i ds =100ma n mosfet 0.35 0.5 sw leakage current (per channel) i lsw 0.01 1 a high efficiency 96 % en threshold high v eh 1.5 v en threshold low v el 0.3 v en leakage current i en 0.01 a over temperature protection otp 150 c otp hysteresis oth 30 c
6 , power analog microelectronics inc www.poweranalog.com efficiency vs output current (vo=1.5v) efficiency vs output current ( ) vo=1.8v efficiency vs output current ( ) vo=2.5v efficiency vs output current 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) 2.5v 3.6v 4.2v 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) 2.5v 3.6v 4.2v 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) 3v 3.6v 4.2v 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) 3v 3.6v 4.2v (vo=2.8v) eifficiency vs output current (vo=3.3v) 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) vin=3.6v vin=4.2v vin=5v efficiency vs output current (vo=1.2v) typical performance characteristics c t =25 , c =10 f, c =10 f, l=4.7 h, unless otherwise noted. aino ?? 0 10 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) vin= 3.6v vin= 4.2v vin= 5v PAM2306 dual high-efficiency pwm step-down dc-dc coverter 07/2008 rev 1.0
efficiency vs input voltage ( ) vo=1.5v efficiency vs input voltage ( ) vo=1.8v efficiency vs input voltage ( ) vo=2.8v efficiency vs input voltage ( ) vo=2.5v 7 , power analog microelectronics inc www.poweranalog.com 30 40 50 60 70 80 90 100 2.5 3 3.5 4 4.5 5 5.5 input voltage(v) efficiency(%) 10ma 100ma 800ma 30 40 50 60 70 80 90 100 2.5 3 3.5 4 4.5 5 5.5 input voltage(v) efficiency(%) 10ma 100ma 800ma 30 40 50 60 70 80 90 100 33.544.555.5 input voltage(v) efficiency(%) 10ma 100ma 800ma 30 40 50 60 70 80 90 100 33.544.555.5 input voltage(v) efficiency(%) 10ma 100ma 800ma 0 10 20 30 40 50 60 70 80 90 100 3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5 input voltage(v) eifficiency(%) io=10ma i o= 100ma i o= 800ma eifficiency vs input voltage (vo=3.3v) efficiency input voltage ( ) vs vo=1.2v typical performance characteristics c t =25 , c =10 f, c =10 f, l=4.7 h, unless otherwise noted. aino ?? 30 40 50 60 70 80 90 100 33.544.555.5 input voltage(v) efficiency(%) io=10ma io=100ma io=800ma PAM2306 dual high-efficiency pwm step-down dc-dc coverter 07/2008 rev 1.0
8 , power analog microelectronics inc www.poweranalog.com typical performance characteristics c t =25 , c =10 f, c =10 f,l=4.7 h, unless otherwise noted. aino ?? 0.584 0.586 0.588 0.590 0.592 0.594 0.596 0.598 0.600 0.602 23456 input voltage(v) vfb(v) i=100ma i=600ma i=800ma 0.590 0.595 0.600 0.605 0.610 0.615 0.620 0 50 100 150 temperature(c) reference voltage(v) vin=3.6v reference voltage vs input voltage reference voltage vs temperature reference voltage vs load current output voltage vs temperature output voltage load current vs 1.188 1.189 1.19 1.191 1.192 1.193 1.194 20 40 60 80 100 120 140 temperature(c) output voltage(v) vo=1.2v vin=3.6v io=100ma PAM2306 dual high-efficiency pwm step-down dc-dc coverter 07/2008 rev 1.0 0.580 0.583 0.585 0.588 0.590 0.593 0.595 0.598 0.600 0.603 0 200 400 600 800 1000 load current(ma) reference voltage(v) vin=2.7v vin=3.6v vin=4.2v 1.188 1.193 1.198 1.203 1.208 1.213 1.218 0 100 200 300 400 500 600 700 800 900 1000 load current(ma) output voltage(v) vin=2.7v vin=3.6v vin=4.2v vin=5v 1.188 1.193 1.198 1.203 1.208 1.213 1.218 2.533.544.555.5 input voltage(v) output voltage(v) io=1ma io=500ma io=1a output voltage vs input voltage vo=1.2v
0.1 0.15 0.2 0.25 0.3 0.35 0.4 23456 input voltage(v) rds(on) 0 0.1 0.2 0.3 0.4 0.5 0.6 20 70 120 temperature(c) rds(on) vin=4.2v vin=3.6v vin=2.7v vin=3.6v 1.2 1.3 1.4 1.5 1.6 1.7 1.8 2345 supply voltage(v) oscillator fr equency(mhz) 1.50 1.52 1.54 1.56 1.58 20 40 60 80 100 120 140 temperature(c) oscillator fr equency(mhz) r vs input voltage dson rdson vs temperature oscillator frequency vs supply voltage oscillator frequency vs temperature vin=3.6v vin=3.6v vin=3.6v 0 5 10 15 20 25 30 35 40 45 50 2.533.544.555.5 input voltage(v) dynamic supply current(ua) dynamic supply current vs input voltage vo=1.2v iload=0a 0 10 20 30 40 50 60 40 60 80 100 120 140 temperature(c) dynamic supply current(ua) dynamic supply current vs temperature vo=1.2v vin=3.6v iload=0a 9 , power analog microelectronics inc www.poweranalog.com typical performance characteristics t =25 c, c =10 f, c =10 f,l=4.7 h, unless otherwise noted. aino o ?? PAM2306 dual high-efficiency pwm step-down dc-dc coverter 07/2008 rev 1.0
load transient io=0-500ma vo=3.3v vin=5v load transient io=0-1a vo=1.2v vin=3.6v typical performance characteristics c t =25 ,c =10 f, c =10 f,l=4.7 h, unless otherwise noted. ain o ?? start-up from shutdown vo=1.8v,vin=3.6v voltage output enable inductor current voltage output output current voltage output output current 10 , power analog microelectronics inc www.poweranalog.com PAM2306 dual high-efficiency pwm step-down dc-dc coverter 07/2008 rev 1.0
application information the basic PAM2306 application circuit is shown in page 1. external component selection is determined by the load requirement, selecting l first and then cin and cout. for most applications, the value of the inductor will fall in the range of 1h to 4.7h. its value is chosen based on the desired ripple current. large value inductors lower ripple current and small value inductors result in higher ripple currents. higher v or vout also increases the ripple current as shown in equation 1. a reasonable starting point for setting ripple current is i = 400ma (40% of 1a). (1) the dc current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. thus, a 1.4a rated inductor should be enough for most applications (1a + 400ma). for better efficiency, choose a low dc-resistance inductor. in continuous mode, the source current of the top mosfet is a square wave of duty cycle vout/vin. to prevent large voltage transients, a low esr input capacitor sized for the maximum rms current must be used. the maximum rms capacitor current is given by: this formula has a maximum at v =2vout, where i =i /2. this simple worst-case condition is commonly used for design because even significant deviations do not offer much relief. note that the capacitor manufacturer's ripple current ratings are often based on 2000 hours of life. this makes it advisable to further derate the capacitor, or choose a capacitor rated at a higher temperature than required. consult the manufacturer if there is any question. the selection of cout is driven by the required effective series resistance (esr). typically, once the esr requirement for cout has been met, the rms current rating generally far exceeds the i (p-p) requirement. the output ripple vout is determined by: where f = operating frequency, c =output capacitance and i = ripple current in the inductor. for a fixed output voltage, the output ripple is highest at maximum input voltage since i increases with input voltage. higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. their high ripple current, high voltage rating and low esr make them ideal for switching regulator applications. using ceramic capacitors can achieve very low output ripple and small circuit size. when choosing the input and output ceramic capacitors, choose the x5r or x7r dielectric formulations. these dielectrics have the best temperature and voltage characteristics of all the ceramics for a given value and size. inductor selection c and c selection using ceramic input and output capacitors in l in rms out ripple out l l in out thermal consideration thermal protection limits power dissipation in the PAM2306. when the junction temperature exceeds 150c, the otp (over temperature protection) starts the thermal shutdown and turns the pass transistor off. the pass transistor resumes operation after the junction temperature drops below 120c. for continuous operation, the junction temperature should be maintained below 125c. the power dissipation is defined as: i is the step-down converter quiescent current. the term tsw is used to estimate the full load step-down converter switching losses. q 1 2 out in out in rms omax in vvv c required i i v out l out 1 viesr+ 8fc

out out l in 1v i= v 1- fl v o dsonh in o dsonl 2 do swsoq in in vr + v -v r p=i + t fi +i v v vo 1.2v 1.5v 1.8v 2.5v 3.3v l 2.2h 2.2h 2.2h 4.7h 4.7h 11 , power analog microelectronics inc www.poweranalog.com PAM2306 dual high-efficiency pwm step-down dc-dc coverter 07/2008 rev 1.0
for the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: since r , quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input voltage range. the maximum power dissipation depends on the thermal resistance of ic package, pcb layout, the rate of surrounding airflow and temperature difference between junction and ambient. the maximum power dissipation can be calculated by the following formula: where tj(max) is the maximum allowable junction temperature 125c.t is the ambient temperature and is the thermal resistance from the junction to the ambient. based on the standard jedec for a two layers thermal test board, the thermal resistance of dfn3x3 is 60c/w. the maximum power dissipation at t = 25c can be calculated by following formula: p =(125c-25c)/60c/w=1.66w the internal reference is 0.6v (typical). the output voltage is calculated as below: the output voltage is given by table 1. resistor selection for output voltage setting as the input voltage approaches the output voltage, the converter turns the p-channel transistor continuously on. in this mode the output voltage is equal to the input voltage minus the voltage drop across the p - channel transistor: v=vCi (r+r) where r = p-channel switch on resistance, i = output current, r = inductor dc resistance the reference and the circuit remain reset until the vin crosses its uvlo threshold. the PAM2306 has an internal soft-start circuit that limits the in-rush current during start-up. this prevents possible voltage drops of the input voltage and eliminates the output voltage overshoot. the soft-start acts as a digital circuit to increase the switch current in several steps to the p-channel current limit (1500ma). the switch peak current is limited cycle-by-cycle to a typical value of 1500ma. in the event of an output voltage short circuit, the device operates with a frequency of 400khz and minimum duty cycle, therefore the average input current is typically 200ma. when the die temperature exceeds 150c, a reset occurs and the reset remains until the temperature decrease to 120c, at which time the circuit can be restarted. ds(on) a ja ja a d out in load dson l dson load l setting the output voltage table 1: 100% duty cycle operation uvlo and soft-start short circuit protection thermal shutdown o r1 v =0.61+ r2 vo r1 r2 1.2v 100k 100k 1.5v 150k 100k 1.8v 200k 100k 2.5v 380k 120k 3.3v 540k 120k 2 do dsonhqin p=i r +iv j(max) a d ja t-t p= 12 , power analog microelectronics inc www.poweranalog.com PAM2306 dual high-efficiency pwm step-down dc-dc coverter 07/2008 rev 1.0
pcb layout check list when laying out the printed circuit board, the following checklist should be used to ensure proper operation of the PAM2306. these items are also illustrated graphically in figure 1. check the following in your layout: 1. the power traces, consisting of the gnd trace, the sw trace and the vin trace should be kept short, direct and wide. 2. does the fb pin connect directly to the feedback resistors? the resistive divider r1/r2 must be con- nected between the (+) plate of c and ground. 3. does the (+) plate of cin connect to vin as closely as possible? this capacitor provides the ac current to the internal power mosfets. 4. keep the switching node, sw, away from the sensitive fb node. 5. keep the (?) plates of c and c as close as possible. top bottom out in out figure 1 :PAM2306 suggested layout 13 , power analog microelectronics inc www.poweranalog.com PAM2306 dual high-efficiency pwm step-down dc-dc coverter 07/2008 rev 1.0
PAM2306 dual high-efficiency pwm step-down dc-dc coverter 14 , power analog microelectronics inc www.poweranalog.com 07/2008 rev 1.0 PAM2306xxxv v 12 output voltage 1 number of pins package type pin configuration output voltage pin configuration package type number of pins v 1 v 2 atype 1. vin2 2. lx2 3. gnd 4. fb1 5. nc1 6. en1 7. vin1 8. lx1 9. gnd 10. fb2 11: nc2 12 :en2 y: wdfn 3x3 p: 12 k: 3.3v h: 2.8v g: 2.5v e: 1.8v c: 1.5v b: 1.2v a: adj k: 3.3v h: 2.8v g: 2.5v e: 1.8v c: 1.5v b: 1.2v a: adj ordering information part number marking package type standard package PAM2306aypv 1 v 2 2306v 1 v 2 xxxyw wdfn3x3-12 3,000 units/tape&reel output voltage 2
PAM2306 dual high-efficiency pwm step-down dc-dc coverter 15 , power analog microelectronics inc www.poweranalog.com 07/2008 rev 1.0 3x3mmwdfn12 outline dimensions dimensions in millimeters dimensions in inches symbol min max min max a0 . 700 0 . 800 0 . 028 0 . 031 a1 0 . 000 0 . 050 0 . 000 0 . 002 a3 0 . 175 0 . 250 0 . 007 0 . 010 b0 . 150 0 . 250 0 . 006 0 . 010 d2 . 950 3 . 050 0 . 116 0 . 120 d2 2 . 300 2 . 650 0 . 091 0 . 104 e2 . 950 3 . 050 0 . 116 0 . 120 e2 1 . 400 1 . 750 0 . 055 0 . 069 e0 . 450 0 . 018 l0 . 350 0 . 450 0 . 014 0 . 018 11 2 2 note : the configuration of the pin # 1 identifier is optional , but must be located within the zone indicated . detail a pin # 1 id and tie bar mark options

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