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general description the max8506/max8507/max8508 integrate a pwm step-down dc-dc regulator and a 75m ? (typ) bypass fet to power the pa in wcdma and cdmaone cell phones.the supply voltage range is from 2.6v to 5.5v, and the guaranteed output current is 600ma. one megahertz pwm switching allows for small external components. the max8506 and max8507 are dynamically controlled to provide varying output voltages from 0.4v to 3.4v. the max8508 is externally programmed for fixed 0.75v to 3.4v output. digital logic enables a high-power (hp) bypass mode that connects the output directly to the bat- tery for all versions. the max8506/max8507/max8508 are designed so the output settles in less than 30? for a full-scale change in output voltage and load current. the max8506/max8507/max8508 are offered in 16-pin 4mm x 4mm thin qfn packages (0.8mm max height). applications wcdma/ncdma cell phoneswireless pdas, palmtops, and notebook computers wireless modems features ? integrated 75m ? (typ) bypass fet ? 38mv dropout at 600ma load ? up to 94% efficiency ? dynamically adjustable output from 0.4v to 3.4v(max8506, max8507) ? externally fixed output from 0.75v to 3.4v(max8508) ? 1mhz fixed-frequency pwm switching ? 600ma guaranteed output current ? shutdown mode 0.1a (typ) ? 16-pin thin qfn (4mm x 4mm, 0.8mm max height) max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets ________________________________________________________________ maxim integrated products 1 ordering information 19-2918; rev 1; 1/04 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. part temp range pin-package max8506 ete -40? to +85? 16 thin qfn max8507 ete -40? to +85? 16 thin qfn max8508 ete -40? to +85? 16 thin qfn cdmaone is a trademark of cdma development group. pin configurations appear at end of data sheet. typical application circuits continued at end of data sheet. current- limit control pwm dac battp lx out comp pgnd gnd refin 1mhz osc ref hp input 2.6v to 5.5v 4.7 h output 0.4v to 3.4v or v batt 4.7 f 0.3 ? 0.4 ? 0.075 ? batt ref 2.2 f 0.22 f skip shdn r c * c c * max8506max8507 * 1015 r c (k ? ) 15001000 c c (pf) 100100 c f (pf) max8506max8507 c f * t ypical application circuits (max8506/max8507) downloaded from: http:///
max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. battp, batt, out, shdn , skip , hp, refin, fb to gnd ...........................................................-0.3v to +6v pgnd to gnd .......................................................-0.3v to +0.3v batt to battp......................................................-0.3v to +0.3v out, comp, ref to gnd.......................-0.3v to (v batt + 0.3v) lx current (note 1) ...............................................................1.6a out current (note 1)............................................................3.2a output short-circuit duration.....................................continuous continuous power dissipation (t a = +70?) 16-pin thin qfn (derate 16.9mw/? above +70?) ...1.349w operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? electrical characteristics(v batt = v battp = 3.6v, shdn = skip = batt, hp = gnd, v refin = 1.932v (max8506), v refin = 1.70v (max8507), c ref = 0.22?, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 2) parameter conditions min typ max units input batt voltage 2.6 5.5 v undervoltage lockout threshold v batt rising 2.150 2.35 2.575 v undervoltage lockout hysteresis 40 mv skip = gnd (normal mode) 180 250 quiescent current skip = batt, 1mhz switching 1750 ? quiescent current in dropout hp = batt 775 1000 ? shutdown supply current shdn = gnd 0.1 5 a v refin = 1.932v, i out = 0 to 600ma (max8506) 3.375 3.40 3.425 v refin = 0.426v, i out = 0 to 30ma (max8506) 0.740 0.75 0.760 v refin = 1.700v, i out = 0 to 600ma (max8507) 3.375 3.40 3.425 out voltage accuracy v refin = 0.375v, i out = 0 to 30ma (max8507) 0.740 0.75 0.760 v max8506 250 485 out input resistance max8507 275 535 k ? refin input current -1 0.1 +1 ? max8506 1.76 refin to out gain max8507 2.00 v/v reference voltage 1.225 1.25 1.275 v reference load regulation 10? < i ref < 100? 2.5 8.5 mv reference bypass capacitor 0.1 0.22 ? fb voltage accuracy fb = comp (max8508) 0.7275 0.75 0.7725 v fb input current v fb = 1v (max8508) 0.03 0.175 ? v batt = 3.6v 0.4 0.825 p-channel on-resistance i lx = 180ma v batt = 2.6v 0.5 ? v batt = 3.6v 0.3 0.5 n-channel on-resistance i lx = 180ma v batt = 2.6v 0.35 ? hp/bypass p-channelon-resistance i out = 180ma, v batt = 3.6v 0.075 0.110 ? note 1: lx has internal clamp diodes to pgnd and batt. applications that forward bias these diodes should take care not to exceedthe ic? package power-dissipation limits. downloaded from: http:///
max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets _______________________________________________________________________________________ 3 parameter conditions min typ max units p-channel current-limitthreshold 1.00 1.25 1.50 a skip = batt (pwm mode) -0.6 -0.45 -0.30 n-channel current-limitthreshold skip = gnd (normal mode) 0.03 0.05 0.07 a p-channel pulse-skippingcurrent threshold skip = gnd (normal mode) 0.050 0.125 0.170 a hp/bypass p-channelcurrent-limit threshold v out = 3.1v 0.8 1.5 2.5 a lx leakage current -2 0.01 +2 ? out leakage current -2 0.01 +2 ? maximum duty cycle 100 % skip = gnd (normal mode) 0 minimum duty cycle skip = batt 12 % comp clamp low voltage 0.8 v comp clamp high voltage 2.0 v max8506 85 150 215 max8507 75 130 188 transconductance max8508 150 260 376 ? current-sense transresistance 0.36 0.48 0.60 v/a oscillator internal oscillator frequency 0.8 1 1.2 mhz logic inputs ( shdn , hp, skip ) logic-input high voltage v batt = 2.6v to 5.5v 1.6 v logic-input low voltage v batt = 2.6v to 5.5v 0.4 v logic input current 0.1 1 ? thermal shutdown thermal-shutdown temperature +160 ? thermal-shutdown hysteresis 15 ? electrical characteristics (continued)(v batt = v battp = 3.6v, shdn = skip = batt, hp = gnd, v refin = 1.932v (max8506), v refin = 1.70v (max8507), c ref = 0.22?, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 2) note 2: specifications to -40? are guaranteed by design, not production tested. downloaded from: http:///
max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets 4 _______________________________________________________________________________________ t ypical operating characteristics (v batt = v battp = 3.6v, shdn = skip = batt, hp = gnd, t a = +25?, unless otherwise noted.) (see the typical application circuits .) efficiency vs. output voltage in normal mode max8506 toc01 output voltage (v) efficiency (%) 3.0 2.5 2.0 1.5 1.0 0.5 60 70 80 90 100 50 0 3.5 r load = 15 ? r load = 10 ? r load = 5 ? skip = gnd efficiency vs. output voltage in pwm mode max8506 toc02 output voltage (v) efficiency (%) 3.0 2.5 2.0 1.5 1.0 0.5 60 70 80 90 100 50 0 3.5 r load = 15 ? r load = 10 ? r load = 5 ? efficiency vs. input voltage 5.0 4.5 4.0 3.5 3.0 2.5 5.5 max8506 toc03 input voltage (v) efficiency (%) 60 70 80 90 100 50 v out = 0.4v v out = 1.2v v out = 3.4v skip = gndr load = 10 ? load current (ma) 100 10 1 1000 efficiency vs. load current max8506 toc04 efficiency (%) 60 70 80 90 100 50 v out = 2.5v; normal mode v out = 2.5v; pwm v out = 1.2v; normal mode v out = 1.2v; pwm dropout voltage vs. load current max8506 toc05 load current (ma) output voltage (mv) 1500 1000 500 30 60 90 120 150 0 0 2000 v in = 3.6v hp = batt supply current vs. supply voltage in pwm mode max8506 toc06 supply voltage (v) supply current (ma) 5.0 4.5 4.0 3.5 3.0 2.5 1 2 3 4 5 60 2.0 5.5 v out = 1.2v v out = 0.4v 200 300 400 500 600 700 800 900 1000 100 supply current vs. supply voltage in normal mode max8506 toc07 supply voltage (v) supply current ( a) 5.0 4.5 4.0 3.5 3.0 2.5 2.0 5.5 v out = 1.2v v out = 3.4v v out = 0.4v skip = gnd heavy-load switching waveform max8506 toc08 1 s/div v lx 2v/divv out ac-coupled20mv/div v out = 1.2v load = 10 ? downloaded from: http:///
max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets _______________________________________________________________________________________ 5 max8506 toc09 400 s/div v lx 2v/divv out ac-coupled5mv/div light-load switching waveform in pwm mode v out = 0.4v load = 10 ? light-load switching waveform in normal mode max8506 toc10 1 s/div v lx 2v/divv out ac-coupled20mv/div v out = 0.4v load = 10 ?, skip = gnd exiting and entering shutdown max8506 toc11 100 s/div v out 1v/div shdn2v/div v out = 1.8v, r load = 10 ? refin transient response max8506 toc12 20 s/div v out 1v/div 0 0 refin1v/div skip = gnd skip = batt v refin = 0.284v to 1.420v hp transient response max8506 toc13 20 s/div v out 1v/div 1.8v 0 hp1v/div skip = gnd skip = batt v out = 1.8v, r load = 10 ? line transient response max8506 toc14 20 s/div v in 200mv/div 3.4v v out ac-coupled20mv/div v out = 1.2v, r load = 10 ? t ypical operating characteristics (continued) (v batt = v battp = 3.6v, shdn = skip = batt, hp = gnd, t a = +25?, unless otherwise noted.) (see the typical application circuits .) downloaded from: http:///
max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets 6 _______________________________________________________________________________________ detailed description the max8506/max8507/max8508 pwm step-down dc-dc converters with integrated bypass pfet are opti- mized for low-voltage, battery-powered applications where high efficiency and small size are priorities. an analog control signal dynamically adjusts the max8506/ max8507s?output voltage from 0.4v to 3.4v with a set- tling time of 30?. the max8508 uses external feedback resistors to set the output voltage from 0.75v to 3.4v. the max8506/max8507/max8508 operate at a high 1mhz switching frequency that reduces external com- ponent size. each device includes an internal synchro-nous rectifier for high efficiency, which eliminates the need for an external schottky diode. the normal operat- ing mode uses constant-frequency pwm switching at medium and heavy loads and automatically pulse skips at light loads to reduce supply current and extend bat- tery life. a forced-pwm mode switches at a constant frequency, regardless of load, to provide a well-con- trolled spectrum in noise-sensitive applications. battery life is maximized by the low-dropout (75m ? ) high- power mode and a 0.1? (typ) logic-controlled shut- down mode. pin description pin max8506 max8507 max8508 name function 11 shdn shutdown control input. drive low for shutdown mode. connect to batt or logic high toenable the ic. 22 gnd ground. connect to pgnd and directly to ep. 33 ref reference output. output of the internal 1.25v reference. bypass to gnd with a 0.22?capacitor. 4 refin external reference input. connect to the output of a digital-to-analog converter fordynamic adjustment of the output voltage. 55 comp compensation. connect a compensation network from comp to gnd to stabilize theregulator. see the typical application circuits . 66h p high-power bypass control input. drive low for out to regulate to the voltage set byrefin (max8506/max8507) or the external resistors on fb (max8508). drive hp high for out to be connected to batt by an internal bypass pfet. 77 n.c. no connection. connect to pgnd. 88 pgnd power ground. connect to gnd. 99l x inductor connection to the drains of the internal power mosfets. lx is high impedancein shutdown mode. 10 10 battp supply voltage input. connect to a 2.6v to 5.5v source. bypass battp to pgnd with alow-esr 2.2? capacitor. connect battp to batt. 11, 13, 15 11, 13, 15 batt supply voltage input. connect all batt pins to battp. 12, 14 12, 14 out regulator output. connect both out pins directly to the output voltage. 16 16 skip skip control input. connect to gnd or drive low to enable pulse skipping under lightloads. connect skip to batt or logic high for forced-pwm mode. ?f b output feedback sense input. to set the output voltage, connect fb to the center of anexternal resistive voltage-divider between out and gnd. fb voltage regulates to 0.75v when hp is low. ep exposed pad. connect directly to gnd underneath the ic. downloaded from: http:///
max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets _______________________________________________________________________________________ 7 pwm control the max8506/max8507/max8508 use a fixed-frequen- cy, current-mode and pwm controller capable of achiev- ing 100% duty cycle. current-mode feedback provides cycle-by-cycle current limiting and superior load and line response, as well as overcurrent protection for the inter- nal mosfet and rectifier. a comparator at the p-channel mosfet switch detects overcurrent at 1.25a. during pwm operation, the max8506/max8507/ max8508 regulate the output voltage by switching at a constant frequency and then modulating the duty cycle with pwm control. the error-amp output, the main switch current-sense signal, and the slope-compensa- tion ramp are all summed using a pwm comparator. the comparator modulates the output power by adjust- ing the peak inductor current during the first half of each cycle based on the output-error voltage. the max8506/max8507/max8508 have relatively low ac loop gain coupled with a high-gain integrator to enable the use of a small and low-valued output filter capaci- tor. the resulting load regulation is 0.1% at 0 to 600ma. normal-mode operation connecting skip to gnd enables normal operation. this allows automatic pwm control at medium and heavyloads and skip mode at light loads to improve efficiency and reduce quiescent current to 180?. operating in normal mode allows the max8506/max8507/max8508 to pulse skip when the peak inductor current drops below 90ma. during skip operation, the max8506/ max8507/max8508 switch only as needed to service the load, reducing the switching frequency and associat- ed losses in the internal switch and synchronous rectifier. there are three steady-state operating conditions for the max8506/max8507/max8508 in normal mode: 1) the device performs in continuous conduction for heavy loads in a manner identical to forced-pwm mode. 2) the inductor current becomes discontinuous at medium loads, requiring the synchronous rectifier to be turned off before the end of a cycle as the inductor current reaches zero. 3) the device enters into skip mode when the converter output voltage exceeds its regulation limit before the inductor current reaches its skip threshold level. during skip mode, a switching cycle initiates when the output voltage has dropped out of regulation. the p- channel mosfet switch turns on and conducts current to the output-filter capacitor and load until the inductor current reaches the pulse-skipping current threshold. then the main switch turns off and the magnetic field inthe inductor collapses while current flows through the synchronous rectifier to the output filter capacitor and the load. the synchronous rectifier is turned off when the inductor current reaches zero. the max8506/ max8507/max8508 wait until the skip comparator senses a low output voltage again. forced-pwm operation connect skip to batt for forced-pwm operation. forced-pwm operation is desirable in sensitive rf anddata-acquisition applications to ensure that switching harmonics do not interfere with sensitive if and data- sampling frequencies. a minimum load is not required during forced-pwm operation since the synchronous rectifier passes reverse-inductor current as needed to allow constant-frequency operation with no load. forced- pwm operation uses higher supply current with no load (1.75ma typ) compared to skip mode (180? typ). 100% duty-cycle operation and dropout the maximum on-time can exceed one internal oscilla-tor cycle, which permits operation at 100% duty cycle. near dropout, cycles can be skipped, reducing switch- ing frequency. however, voltage ripple remains small because the current ripple is still low. as the input volt- age drops even further, the duty cycle increases until the internal p-channel mosfet stays on continuously. dropout voltage at 100% duty cycle is the output cur- rent multiplied by the sum of the internal pmos on- resistance (400m ? typ) and the inductor resistance. for lower dropout, use the high-power bypass mode(75m ? typ). high-power bypass mode a high-power bypass mode is available for use when apa transmits at high power. this mode connects out to batt through the bypass pfet. additionally, the pwm buck converter is forced into 100% duty cycle to further reduce dropout. the dropout in the bypass pfet equals the load current multiplied by the on-resis- tance (75 ? typ) in parallel with the buck converter and inductor dropout resistance. undervoltage lockout (uvlo) the max8506/max8507/max8508 do not operate withbattery voltages below the uvlo threshold of 2.35v (typ). the output remains off until the supply voltage exceeds the uvlo threshold. this guarantees the integrity of the output voltage regulation. downloaded from: http:///
max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets 8 _______________________________________________________________________________________ synchronous rectification an n-channel synchronous rectifier operates during thesecond half of each switching cycle (off-time). when the inductor current falls below the n-channel current- comparator threshold or when the pwm reaches the end of the oscillator period, the synchronous rectifier turns off. this prevents reverse current from the output to the input in pulse-skipping mode. during pwm oper- ation, the neglim threshold adjusts to permit reverse current during light loads. this allows regulation with a constant switching frequency and eliminates minimum load requirements for fixed-frequency operation. shutdown mode drive shdn to gnd to place the max8506/max8507/ max8508 in shutdown mode. in shutdown, the refer- ence, control circuitry, internal switching mosfet, and synchronous rectifier turn off and the output becomes high impedance. input current falls to 0.1? (typ) dur- ing shutdown mode. drive shdn high to enable the ic. current-sense comparators the max8506/max8507/max8508 use several internalcurrent-sense comparators. in pwm operation, the pwm comparator terminates the cycle-by-cycle on-time and provides improved load and line response. a second cur- rent-sense comparator used across the p-channel switch controls entry into skip mode. a third current-sense com- parator monitors current through the internal n-channelmosfet to prevent excessive reverse currents and determine when to turn off the synchronous rectifier. a fourth comparator used at the p-channel mosfet detects overcurrent. a fifth comparator used at the bypass p-channel mosfet detects overcurrent in the hp mode or at dropout. this protects the system, exter- nal components, and internal mosfets under overload conditions. applications information setting the output voltage using a dac (max8506/max8507) the max8506/max8507 are optimized for highest sys-tem efficiency when applying power to a linear pa in cdma handsets. when transmitting at less than full power, the supply voltage to the pa is lowered in many steps from 3.4v to as low as 0.4v to greatly reduce bat- tery current (see the typical application circuits ). the use of dc-dc converters such as the max8506/max8507 dramatically extends talk time in these appli- cations. the max8506/max8507s?output voltage is dynamicallyadjustable from 0.4v to 3.4v by the use of the refin input. the gain from v refin to v out is internally set to 1.76 (max8506) or 2.00 (max8507). v out can be adjust- ed during operation by driving refin with an externaldac. the max8506/max8507 output responds to full- scale change in voltage and current in less than 30?. using external divider (max8508) the max8508 is intended for two-step v cc control applications where high efficiency is a priority. selectan output voltage between 0.75v and 3.4v by connect- ing fb to a resistive-divider between the output and gnd (see the max8508 typical application circuit ). select feedback resistor r2 in the 5k ? to 50k ? range. r1 is then given by:where v fb = 0.75v. input capacitor selection capacitor esr is a major contributor to input ripple inhigh-frequency dc-dc converters. ordinary aluminum- electrolytic capacitors have high esr and should be avoided. low-esr tantalum or polymer capacitors are better and provide a compact solution for space-con- strained surface-mount designs. ceramic capacitors have the lowest overall esr. the input filter capacitor reduces peak currents and noise at the input voltage source. connect a low-esr bulk capacitor (2.2? to 10?) to the input. select this bulk capacitor to meet the input ripple requirements and voltage rating rather than capacitance value. use the following equation to calculate the maximum rms input current: compensation, stability, and output capacitor the max8506/max8507/max8508 are externally com-pensated by placing a resistor and a capacitor (see the typical application circuits , r c and c c ) in series from comp to gnd. an additional capacitor (c f ) may be required from comp to gnd if high-esr output capaci- tors are used. the c c capacitor integrates the current from the transimpedance amplifier, averaging output i i v vvv rms out in out in out = () rr v v out fb 12 1 = ?? ? ?? ? downloaded from: http:///
max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets _______________________________________________________________________________________ 9 capacitor ripple. this sets the device speed for transientresponse and allows the use of small ceramic output capacitors because the phase-shifted capacitor ripple does not disturb the current-regulation loop. the resistor sets the proportional gain of the output error voltage by a factor of g m x r c . increasing this resistor also increas- es the sensitivity of the control loop to output ripple.the resistor and capacitor set a compensation zero that defines the system? transient response. the load cre- ates a dynamic pole, shifting in frequency with changes in load. as the load decreases, the pole frequency shifts to the left. system stability requires that the com- pensation zero must be placed to ensure adequate phase margin (at least 30 at unity gain). with a 4.7? output capacitor, the recommended c c and r c for the max8506 are 1500pf and 10k ? , respectively. this pro- vides adequate phase margin over the entire outputvoltage and load range and optimizes the output- voltage settling time for refin dynamic control. see the typical application circuits for recommended c c and r c values for the max8507 and max8508. inductor selection a 4? to 6h inductor is recommended for most appli- cations. for best efficiency, the inductor? dc resistance should be <400m ? . saturation current (i sat ) should be greater than the maximum dc load at the pa? supplyplus half the inductor current ripple. two-step v cc applications typically require very small inductors withi sat in the 200ma to 300ma region. see tables 1 and 2 for recommended inductors and suppliers. pc board layout and routing high switching frequencies and large peak currentsmake pc board layout a very important part of design. good design minimizes emi, noise on the feedback paths, and voltage gradients in the ground plane, all of which can result in instability or regulation errors. connect the inductor, input filter capacitor, and output fil- ter capacitor as close together as possible and keep their traces short, direct, and wide. the external voltage- feed- back network should be very close to the fb pin, within 0.2in (5mm). keep noisy traces, such as those from the lx pin, away from the voltage-feedback network. position the bypass capacitors as close as possible to their respective supply and ground pins to minimize noise cou- pling. for optimum performance, place input and output capacitors as close to the device as possible. connect gnd directly under the ic to the exposed paddle. referto the max8506 evaluation kit for an example pc board layout and routing scheme. supplier phone website murata 770-436-1300 www.murata.com sumida 847-956-0666 www.sumida.com taiyo yuden 408-573-4150 www.t-yuden.com toko 847-297-0070 www.tokoam.com table 2. component suppliers table 1. suggested inductors supplier part number inductance (h) esr (m ? ) saturationcurrent (a) dimensions (mm) murata lqh32c-53 4.7 150 0.650 2.5 x 3.2 x 1.7 sumida cdrh2d11 4.7 135 0.500 3.2 x 3.2 x 1.2 taiyo yuden lblq2016 4.7 250 0.210 1.6 x 2.0 x 1.6 toko d312c 4.7 200 0.790 3.6 x 3.6 x 1.2 downloaded from: http:///
max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets 10 ______________________________________________________________________________________ 16 15 14 13 battout batt 9 10 11 12 lx battp batt out 4 3 2 1 fb ref gnd 5678 comp hp n.c. pgnd shdn skip thin qfn 4mm x 4mm 16 15 14 13 battout batt 9 10 11 12 lx battp batt out 4 3 2 1 refin ref gnd 5678 comp hp n.c. pgnd shdn skip thin qfn 4mm x 4mm top view max8508 max8506max8507 pin configurations current- limit control pwm battp lx out fb comp pgnd gnd 1mhz osc ref hp input 2.6v to 5.5v 4.7 h output 0.75v to 3.4v or v batt 4.7 f 0.3 ? 0.4 ? 0.075 ? batt ref 2.2 f 0.22 f skip shdn r c 5.6k ? c c 2700pf c f 100pf max8508 0.75v r1r2 t ypical application circuits (max8508) (continued) chip information transistor count: 2020process: bicmos downloaded from: http:///
max8506/max8507/max8508 pwm step-down dc-dc converters with 75m ? ? bypass fet for wcdma and cdmaone handsets maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 11 2004 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline information, go to www.maxim-ic.com/packages .) 24l qfn thin.eps c 1 2 21-0139 package outline12, 16, 20, 24l thin qfn, 4x4x0.8mm c 2 2 21-0139 package outline12, 16, 20, 24l thin qfn, 4x4x0.8mm downloaded from: http:///

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