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pam2309 document number: dsxxxxx rev. 2 - 1 1 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated 1a step-down dc-dc converter description the pam2309 is a 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 pam2309 pr ovides a power-saving pulse- skipping modulation (psm) mode to reduce quiescent current under light load operation to save power. the pam2309 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 output voltage is adjustable from 0.6v to the input vo ltage. all versions 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 to prevent deep battery discharge. the pam2309 is available in tsot25, dfn2x2-6 pin and qfn3x3-16 pin packages. features ? efficiency up to 96% ? only 40a (typ) quiescent current ? output current: up to 1a ? internal synchronous rectifier ? 1.5mhz switching frequency ? soft-start ? under-voltage lockout ? short circuit protection ? thermal shutdown ? 5-pin small tsot25, dfn2x2-6 pin and qfn3x3-16 pin packages ? pb-free package applications ? cellular phone ? portable electronics ? wireless devices ? cordless phone ? computer peripherals ? battery powered widgets ? electronic scales ? digital frame pin assignments top view tsot25
pam2309 document number: dsxxxxx rev. 2 - 1 2 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated typical applications circuit v 2 r 1 r 1 5 . 0 o ? ? ? ? ? ? ? ? + = pin descriptions pin name function vin chip main power supply pin. gnd ground en enable control input. force this pin vo ltage above 1.5v, enables the chip, and below 0.3v shuts down the device. vout/fb vout: output voltage feedback pin, an inter nal resistive divider divides the output voltage down for comparison to the internal reference voltage. fb: feedback voltage to internal error amplifier, the threshold voltage is 0.5v. sw the drains of the internal main and synchronous power mosfet. nc not connected functional block diagram
pam2309 document number: dsxxxxx rev. 2 - 1 3 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated 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 +6.0 v en, fb pin voltage -0.3 to v in v sw voltage -0.3 to ( v in +0.3) v junction temperature 150 c storage temperature range -65 to +150 c soldering temperature 300, 5sec c recommended operating conditions (@t a = +25c, unless otherwise specified.) parameter rating unit supply voltage 2.5 to 5.5 v operation temperature range -40 to +85 c junction temperature range -40 to +125 thermal information parameter package symbol max unit thermal resistance (junction to case) tsot25 (note 1) jc 130 c/w dfn2x2 20 qfn3x3 12 thermal resistance (junction to ambient) tsot25 ja 102 dfn2x2 68 qfn3x3 34 internal power dissipation tsot25 p d 400 mw dfn2x2 980 qfn3x3 1470 note: 1. the maximun output current for tsot25 package is limited by internal power dissipation capacity as described in application information hereinafter.
pam2309 document number: dsxxxxx rev. 2 - 1 4 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated electrical characteristics (@t a = +25c, v in = 3.6v, v o = 1.8v, c in = 10f, c o = 10f, l = 4.7h, unless otherwise specified.) parameter symbol test conditions min typ max units input voltage range v in 2.5 5.5 v regulated feedback voltage v fb 0.490 0.500 0.510 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 in = 3v,v fb = 0.5v or v o = 90% 1.5 a output voltage line regulation lnr v in = 2.5v to 5v, i o = 10ma 0.2 0.5 %/v output voltage load regulation ldr i o = 1ma to 800ma 0.5 1.5 % quiescent current i q no load 40 70 a shutdown current i sd v en = 0v 0.1 1.0 a oscillator frequency f osc v o = 100% 1.2 1.5 1.8 mhz v fb = 0v or v o = 0v 500 khz drain-source on-state resistance r ds(on) i ds = 100ma p mosfet 0.30 0.45 ? n mosfet 0.35 0.50 ? sw leakage current 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
pam2309 document number: dsxxxxx rev. 2 - 1 5 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated typical performance characteristics (@t a = +25c, c in = 10f, c o = 10f, l = 4.7h, unless otherwise specified.)
pam2309 document number: dsxxxxx rev. 2 - 1 6 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated typical performance characteristics (cont.) (@t a = +25c, c in = 10f, c o = 10f, l = 4.7h, unless otherwise specified.)
pam2309 document number: dsxxxxx rev. 2 - 1 7 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated typical performance characteristics (cont.) (@t a = +25c, c in = 10f, c o = 10f, l = 4.7h, unless otherwise specified.)
pam2309 document number: dsxxxxx rev. 2 - 1 8 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated typical performance characteristics (cont.) (@t a = +25c, c in = 10f, c o = 10f, l = 4.7h, unless otherwise specified.)
pam2309 document number: dsxxxxx rev. 2 - 1 9 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated typical performance characteristics (cont.) (@t a = +25c, c in = 10f, c o = 10f, l = 4.7h, unless otherwise specified.)
pam2309 document number: dsxxxxx rev. 2 - 1 10 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated application information the basic pam2309 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 1 h to 4.7 h. 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 in or v out also increases the ripple current as shown in equation 1. a reasonable starting point for setting ripple current is i = 400ma (40% of 1a). ()( ) ? ? ? ? ? ? ? ? ? = 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 1.4a rated inductor should be enough fo r most applications (1a + 400ma). for be tter efficiency, choose a low dc-resista nce inductor. v o 1.2v 1.5v 1.8v 2.5v 3.3v l 2.2h 2.2h 2.2h 4.7h 4.7h 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 c apacitors, choose the x5r or x7r dielectric formulations. thes e dielectrics have th e 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 pam2309. 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.
pam2309 document number: dsxxxxx rev. 2 - 1 11 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 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 tsot25 package is 250c/w, dfn2x2 102c/w, and qfn3x3 68c/w, respectively. the maximum power dissipation at t a = +25c can be calculated by following formula: tsot25 package: p d = (125c - 25c)/250c/w = 0.4w dfn2*2 package: p d = (125c - 25c)/102c/w = 0.984w qfn3*3 package: p d = (125c - 25c)/68c/w =1.47w setting the output voltage the internal reference is 0.5v (typical). the output voltage is calculated as below: ? ? ? ? ? ? + = 2 r 1 r 1 x 5 . 0 v o the output voltage is given by table 1. table 1. resistor selection for output voltage setting. v o r1 r2 1.2v 330k 240k 1.5v 360k 180k 1.8v 470k 180k 2.5v 510k 130k 3.3v 680k 120k 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 pam2309 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 ac ts as a digital circuit to increase the switch current in several steps to the p- channel current limit (1500ma). short circuit protection 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, ther efore the average input current is typically 200ma. 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.
pam2309 document number: dsxxxxx rev. 2 - 1 12 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated application information (cont.) pcb layout check list when laying out the printed circuit board, the following checklis t should be used to ensure proper operation of the pam2309. th ese items are also illustrated graphically in figure 1. check the following in your layout: 1. the power traces, consisting of t he gnd trace, the sw trace and the v in trace should be kept short, direct and wide. 2. does the v fb pin connect directly to the feedback resistors? the resistiv e divider r1/r2 must be connected between the (+) plate of c out and ground. 3. does the (+) plate of c in connect to v in as closely as possible? this c apacitor provides the ac current to the internal power mosfets. 4. keep the switching node, sw, away from the sensitive v fb node. 5. keep the (?) plates of c in and c out as close as possible. figure 1. pam2309 suggested layout
pam2309 document number: dsxxxxx rev. 2 - 1 13 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated ordering information part number output voltage marking part type standard package pam2309aabadjr adj blayw tsot25 3000 units/tape & reel pam2309bjeadjr adj p2309a qfn3x3 3000 units/tape & reel PAM2309CGFADJR adj blayw dfn2x2-6 3000 units/tape & reel marking information top view tsot25
pam2309 document number: dsxxxxx rev. 2 - 1 14 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated package outline dimensions (all dimensions in mm.) tsot25
pam2309 document number: dsxxxxx rev. 2 - 1 15 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated package outline dimensions (cont.) (all dimensions in mm.) dfn2x2-6
pam2309 document number: dsxxxxx rev. 2 - 1 16 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 a product line o f diodes incorporated package outline dimensions (cont.) (all dimensions in mm.) qfn3x3-16 notes: 2. controlling dimensions are in millimeters (angles in degress). 3. coplanarity applies to the exposed pad as well as the terminals. 4. dap is 1.90 x 1.90mm.
pam2309 document number: dsxxxxx rev. 2 - 1 17 of 17 www.diodes.com january 2013 ? diodes incorporated pam2309 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. this document is written in english but may be translated into multiple languages for reference. only the english version of t his document is the final and determinative format released by diodes incorporated. 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 ? 2013, diodes incorporated www.diodes.com

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