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pam2319 document number: dsxxxxx rev. 1 - 1 1 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated dual high-efficiency pwm step-down dc-dc converter description the pam2319 is a dual step-down current-mode, dc-dc converter. at heavy load, the constantf requency pwm control performs excellent stability and transient response. to ensure the longest battery life in portable applications, the pam2319 provides a power- saving pulse-skipping modulation (psm) mode to reduce quiescent current under light load operation. the pam2319 supports a range of input voltages from 2.7v 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 adjustable from 1.0v to 3.3v. both channels employ internal power switch and synchronous rectifier 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 0.1a. other key features include under-voltage lockout, soft-start, short circuit protection and thermal shutdown. features ? supply voltage: 2.7v to 5.5v ? output voltage: ? vo1 adj/1000ma ? vo2 adj/2000ma ? low quiescent current: channel 1: 40a; channel 2: 55a ? high efficiency: ? switching frequency: 3mhz(channel 1) 2.5mhz(channel 2) ? internal synchronous rectifier ? soft start ? under-voltage lockout ? short circuit protection ? thermal shutdown ? small w-dfn3x3-12l pb-free/halogen free package ? rohs/reach compliant pin assignments applications ? portable electronics ? personal information appliances ? wireless and dsl modems
pam2319 document number: dsxxxxx rev. 1 - 1 2 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated typical applications circuit figure 1. adjustable voltage regulator pin descriptions pin number w-dfn3x3-12l pin name function 1 fb2 channel 2 feedback pin internally set to 0.6v. 2 vin2 input voltage pin of channel 2. 3 agnd2 signal ground of channel 2 for small signal components. 4 vin1 input voltage pin of channel 1. 5 pgnd1 main power ground pin of channel 1 6 sw1 channel 1 switching pin. the drains of the internal main and synchronous power mosfet. 7 fb1 channel 1 feedback pin internally set to 0.6v. 8 agnd1 signal ground of channel 1 for small signal components. 9 en1 enable control input. pull logic high to enable vo1. pull logic low to disable. 10 en2 enable control input. pull logic high to enable vo2. pull logic low to disable. 11 pgnd2 main power ground pin of channel 2. 12 sw2 channel 2 switching pin. the drains of the internal main and synchronous power mosfet. ? exposed pad connect to gnd
pam2319 document number: dsxxxxx rev. 1 - 1 3 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated functional block diagram note: 1. the diagram above just shows one channel. absolute maximum ratings (@t a = +25c, unless otherwise specified.) 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. parameter rating unit input voltage -0.3 to 6.5 v en1, fb1, sw1, en2, fb2 and sw2 pin voltage -0.3 to (v in +0.3) v maximum junction temperature 150 c storage temperature range -65 to +150 c soldering temperature 260, 10sec c recommended operating conditions (@t a = +25c, unless otherwise specified.) parameter rating unit supply voltage 2.7 to 5.5 v ambient temperature range -40 to +85 c junction temperature range -40 to +1255 thermal information parameter symbol package max unit thermal resistance (junction to ambient) ja w-dfn3x3-12l 60 c/w thermal resistance (junction to case) jc w-dfn3x3-12l 8.5
pam2319 document number: dsxxxxx rev. 1 - 1 4 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated electrical characteristics (@t a = +25c, v in = 3.3v, v o = 1.8v, c in = 10f, c o = 10f, l = 1h, unless otherwise specified.) channel 1 parameter symbol test conditions min typ max units input voltage range v in 2.7 5.5 v uvlo threshold v uvlo v in rising 2.4 2.5 v hysteresis 240 mv v in falling 1.8 v regulated feedback voltage v fb 0.588 0.600 0.612 v reference voltage line regulation ? v fb 0.3 %/v regulated output voltage accuracy v o i o = 100ma -3 +3 % peak inductor current i pk v o = 90% 1.5 a output voltage line regulation lnr v in = 2.7v to 5v, i o = 10ma 0.2 0.5 %/v output voltage load regulation ldr i o = 1ma to 1000ma -2 +2 % quiescent current i q no load 40 80 a shutdown current i sd v en = 0v 0.1 1 a oscillator frequency f osc v o = 100% 3 mhz v fb = 0v or v o =0v 1 mhz drain-source on-state resisitance r ds(on) p mosfet 0.35 0.45 ? n mosfet 0.35 0.45 ? sw leakage current ilsw 0.01 1 a efficiency output1, i o = 500ma, v in = 3.3v 84 % psm threshold i th v in = 3.3v 100 ma en threshold high v eh 1.5 v en threshold low v el 0.3 v en leakage current i en 0.01 a soft-start t on from en1 to output 2 ms over temperature protection otp 150 c otp hysteresis oth 30 c
pam2319 document number: dsxxxxx rev. 1 - 1 5 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated electrical characteristics (@t a = +25c, v in = 3.3v, v o = 1.2v, c in = 10f, c o = 10f, l = 1h, unless otherwise specified.) channel 2 parameter symbol test conditions min typ max units input voltage range v in 2.7 5.5 v uvlo threshold v uvlo v in rising 2.6 2.7 v hysteresis 250 mv v in falling 12 v regulated feedback voltage v fb 0.588 0.600 0.612 v reference voltage line regulation ? v fb 0.3 %/v regulated output voltage accuracy v o i o = 100ma -3 +3 % peak inductor current i pk v o = 90% 3 a output voltage line regulation lnr v in = 2.7v to 5v, i o = 10ma 0.2 0.5 %/v output voltage load regulation ldr i o = 1ma to 1000ma -2 +2 % quiescent current i q no load 55 100 a shutdown current i sd v en = 0v 0.1 1.0 a oscillator frequency f osc v o = 100% 2.5 mhz drain-source on-state resisitance r ds(on) p mosfet 0.11 ? n mosfet 0.85 ? sw leakage current ilsw 0.01 1 a efficiency output1, i o = 500ma, v in = 3.3v 87 % psm threshold i th v in = 3.3v 250 450 ma en threshold high v eh 1.5 v en threshold low v el 0.3 v en leakage current i en 0.01 a soft-start t on from en1 to output 250 ms over temperature protection otp 150 c otp hysteresis oth 30 c
pam2319 document number: dsxxxxx rev. 1 - 1 6 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated typical performance characteristics (@t a = +25c, v o = 1.8v c in = 10f, c o = 10f, l = 1h, unless otherwise specified.) channel 1
pam2319 document number: dsxxxxx rev. 1 - 1 7 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated typical performance characteristics (cont.) (@t a = +25c, v o = 1.2v c in = 10f, c o = 10f, l = 1h, unless otherwise specified.) channel 2
pam2319 document number: dsxxxxx rev. 1 - 1 8 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated application information the basic pam2319 application circui t is shown in page 2. external component sele ction is determined by the load requirement, s electing l first and then c in and c out . inductor selection for most applications, the value of the inductor will fall in the range of 0.47 h to 2 h. its value is chosen based on the desired ripple current and efficiency. large value inducto rs lower ripple current and small value inductors result in higher ripple currents. higher v in or v out also increases the ripple current as shown in equation. for channel 1, 1a reasonable starting point for setting ripple current is ? i l = 400ma (40% of 1a) and for channel 2, 2a setting ripple current is 800ma. ??? ? ? ? ? ? ? ? ? ? ? ? ? v v 1 v l f 1 i in out out l equation (1) the dc current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prev ent core saturation. thus, a 4.2a rated inductor should be enough fo r most applications (3a + 1.2a). for be tter efficiency, choose a low dc-resistan ce inductor. v o 1.2v 1.5v 1.8v 2.5v 3.3v l 1.2h 1.5h 2.2h 2.2h 2.2h c in and c out selection in continuous mode, the source current of the top mosfet is a square wave of duty cycle v out /v in . 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: ?? ?? v v v v i i required c in 2 / 1 out in out omax rms in ? ? this formula has a maximum at v in = 2v out , where i rms =i out /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 choos e a capacitor rated at a higher temperature than required. con sult the manufacturer if there is any question. the selection of c out is driven by the required effe ctive series resistance (esr). typically, once the esr requirement for c out has been met, the rms current rating generally far exceeds the i ripple (p-p) requirement. the output ripple ? v out is determined by: ?? c f 8 / 1 esr i v out l out ? ? ? ? where f = operating frequency, c out = output capacitance and ? i l = ripple current in the inductor. for a fixed output voltage, the output ripple is highest at maximum input voltage since ? i l increases with input voltage. using ceramic input and output capacitors higher values, lower cost ceramic capacitor s are now becoming available in smaller ca se sizes. their high ripple current, high voltage rating and low esr make them ideal for switching regulator applications. using ceramic capacitors can achi eve very low output ripple and s mall circuit size. when choosing the input and output ceramic capac itors, choose the x5r or x7r dielectric formul ations. these dielectrics have t he best temperature and voltage characteristics of a ll the ceramics for a given value and size. thermal consideration thermal protection limits power dissipation in the pam2319. when t he junction temperature exceeds +150c, the otp (over tempera ture protection) starts the thermal shutdown and turns the pass tr ansistor off. the pass transistor resumes operation after the junc tion temperature drops below +120c. for continuous operation, the junction te mperature should be maintained below +125 c. the power dissipation is defined as: ?? ?? v i i f t v r v v r v i p in q o s sw in l ) on ( ds o in h ) on ( ds o 2 o d ? ? ? ? ? i q is the step-down converter quiescent current. the term tsw is used to estimate the full load step-down converter switching los ses.
pam2319 document number: dsxxxxx rev. 1 - 1 9 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated application information (cont.) for the condition where the step-down converter is in dropout at 100% duty cycle, the tota l device dissipation reduces to: v i r i p in q h ) on ( ds 2 o d ? ? since r ds(on) , quiescent current, and switching losses all vary with input vo ltage, the total losses should be investigated over the complet e input voltage range. the maximum power dissipation depends on the thermal resistance of ic package, pcb layout, the rate of surroundi ng airflow and temperature difference between junction and ambient. the maximu m power dissipation can be calculated by the following formu la: ? ? ? ja a ) max ( j d t t p where t j(max) is the maximum allowable junction temperature +125c. t a is the ambient temperature and ja 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 ja of wdfn3x3 is 60c/w. the maximum power dissipation at t a = +25c can be calculated by following formula: p d = (125c - 25c) /60c/w = 1.67w setting the output voltage the internal reference is 0.6v (typical). the output voltage is calculated as below: the output voltage is given by table 1. ? ? ? ? ? ? ? ? 2 r 1 r 1 x 6 . 0 v o table 1: resistor selection for output voltage setting. v o r1 r2 1.2v 150k 150k 1.5v 150k 100k 1.8v 300k 150k 2.5v 380k 120k 3.3v 680k 150k pulse skipping mode (psm) description when load current decreases, the peak switch current in power- pmos will be lower than skip current threshold and the device wil l enter into pulse skipping mode. in this mode, the device has two states, working state and idle state. first, the device enters in to working state controlled b y internal error amplifier.when the feedback voltage gets higher than internal reference voltage, the device will enter into low i q idle state with most of internal blocks disabled. the output voltage will be reduced by loading or leakage current. when the feedback voltage gets lower than th e internal reference voltage, the convertor will start a working state again. 100% duty cycle operation as the input voltage approaches the output voltage, the converte r turns the p-channel transistor continuously on. in this mode the output voltage is equal to the input voltage minus the vo ltage drop across the p-channel transistor: ?? r r i v v l dson load in out ? ? ? where r ds(on) = p-channel switch on resistance, i load = output current, r l = inductor dc resistance uvlo and soft-start the reference and the circuit remain reset until the v in crosses its uvlo threshold. the pam2319 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. thermal shutdown when the die temperature exceeds +150c, a reset occurs and the reset remains until the temperature decrease to +120c, at whic h time the circuit can be restarted.
pam2319 document number: dsxxxxx rev. 1 - 1 10 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated application information (cont.) short circuit protection channel 1: the swich peak current is limited cycle-by-cycle to a typical v aule in the event of an output vo ltage short circuit. the device operates with a frequency of 1mhz and minimum duty clycle. therefor e the average input current is typical 350ma (v in = 3.3v). channel 2: when the converter output is shorted or t he device is overloaded, each high-side mosfet current-limit event (3a typ) turns off the high-side mosfet and turns on the low-side mosfet. an internal counter is used to count the eac h current-limit event. the counter is rese t after consecutive high-side mosfets turn on wit hout reaching current limit. if the current- limit condition persists, the counter fill s up. the control logic then stops both high-side and lowside mosfets and waits for a hiccup period, before attemping a new soft-start sequence. the co unter bits is decided by v fb voltage. if v fb 0 2, the counter is 3-bit counter; if vfb > 0.2 the count er is 6-bit counter. the typical hicuup made duty cycle is 1.7%. the hiccup mode is dis able during soft-start time. pcb layout check list when laying out the printed circuit board, the following checklis t should be used to ensure proper operation of the pam2319. ch eck the following in your layout: 1. the input capacitor should be clos e to ic as close as possible. 2. minimize the switching loop area to avoid excessive switching noise. 3. two parts gnd should be separately lay out to avoid disturbing by each other. 4. must put a small decoupling capacitor between vin2 pin and agnd2 pin. 5. vo2 output capacitor should be close to output connector to minimize pcb t race resistance affect on ripple voltage. recomme nd use two output capacitor, one close to inductor and ic, another close to output connector. 6. pgnd1 pin should not directly connect to the thermal pad (pgn d), it should connect to input c apacitor gnd then to other gnd. 7. agnd should connect to pgnd at input capacitor gnd. 8. for the good thermal dissipation, pam2316 has a heat dissipate pad in the bottom side, it should be soldered to pcb surface. for the copper area can't be large in the component side, so we c an use multiple vias connect to other side of the pcb. 9. avoid using vias in the high-current paths. if vias are unavoidable, use multiple vias in parallel to reduce resistance and inductance. ordering information part number part marking package type standard package PAM2319AYAA bnaa xxxyw w-dfn3x3-12l 3000 units/tape & reel
pam2319 document number: dsxxxxx rev. 1 - 1 11 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated marking information package outline dimensions (all dimensions in mm.) w-dfn3x3-12
pam2319 document number: dsxxxxx rev. 1 - 1 12 of 12 www.diodes.com november 2012 ? diodes incorporated pam2319 a product line o f diodes incorporated important notice diodes incorporated makes no warranty of any kind, express or implied, with regards to this document, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries rese rve the right to make modifications, enhanc ements, improvements, corrections or ot her changes without further notice to this document and any product descri bed herein. diodes incorporated does not assume any liability ari sing out of the application or use of this document or an y product described herein; neither does di odes incorporated convey any license under its patent or trademark rights, nor the rights of others. any customer or us er of this document or products described herein in such applica tions shall assume all risks of such use and will agree to hold diodes incorporated and all the companies whose products are represented on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability w hatsoever in respect of any products purchased through unauthoriz ed sales channel. should customers purchase or use diodes inco rporated products for any unintended or una uthorized application, customers shall i ndemnify and hold diodes incorporated and its representativ es harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death a ssociated with such unintended or unauthorized application. products described herein may be covered by one or more united states, international or foreign patents pending. product names and markings noted herein may also be covered by one or more united states, international or foreign trademarks. life support diodes incorporated products are specifically not authorized for use as critical component s in life support devices or systems without the express written approval of the chief executive offi cer of diodes incorporated. as used herein: a. life support devices or syst ems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when proper ly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in significant injury to the user. b. a critical component is any component in a life support devic e or system whose failure to perform can be reasonably expect ed to cause the failure of the life support device or to affect its safety or effectiveness. customers represent that they have all necessary expertise in the safety and regulatory ramifi cations of their life support dev ices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-rel ated requirements concerning the ir products and any use of diodes incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or s ystems-related information or support that may be provided by diodes incorporated. further, customers must fully indemnify diodes incorporate d and its representatives against any damages arisi ng out of the use of diodes incorporated pr oducts in such safety-critical, life suppor t devices or systems. copyright ? 2012, diodes incorporated www.diodes.com

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