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general description the max1958/max1959 power amplifier (pa) power- management ics (pmics) integrate an 800ma, dynami- cally adjustable step-down converter, a 5ma rail-to- rail operational amplifier (op amp), and a precision temperature sensor to power a heterojunction bipolar transistor (hbt) pa in w-cdma and n-cdma cell phones. the high-efficiency, pulse-width modulated (pwm), dc- to-dc buck converter is optimized to provide a guaran- teed output current of 800ma. the output voltage is dynamically controlled to produce any fixed-output volt- age in the range of 0.75v to 3.4v (max1958) or 1v to 3.6v (max1959), with settling time less than 30? for a full-scale change in voltage and current. the 1mhz pwm switching frequency allows the use of small external components while pulse-skip mode reduces quiescent current to 190? with light loads. the converter utilizes a low on-resistance internal mosfet switch and synchro- nous rectifier to maximize efficiency and minimize external component count. the 100% duty-cycle opera- tion allows for an ic dropout voltage of only 130mv (typ) at 600ma load. the micropower op amp is used to provide bias to the hbt pa to maximize efficiency. the amplifier features active discharge in shutdown for full pa bias control. it has 5ma rail-to-rail drive capability, 800khz gain-band- width product, and 120db open-loop voltage gain. the precision temperature sensor measures tempera- tures between -40? to +125?, with linear tempera- ture-to-voltage analog output characteristics. the max1958/max1959 are available in a 20-pin 5mm ? 5mm thin qfn package (0.8mm max height). applications w-cdma and n-cdma cellular phones wireless pdas and modems features step-down converter dynamically adjustable output voltage from 0.75v to 3.4v (max1958) dynamically adjustable output voltage from 1v to 3.6v (max1959) 800ma guaranteed output current 130mv ic dropout at 600ma load low quiescent current 190? (typ) in skip mode (max1958) 3ma (typ) in pwm mode 0.1? (typ) in shutdown mode 1mhz fixed-frequency pwm operation 16% to 100% duty-cycle operation no external schottky diode required soft-start operational amplifier 5ma rail-to-rail output active discharge in shutdown 800khz gain-bandwidth product 120db open-loop voltage gain (r l = 100k ? ) temperature sensor accurate sensor -11.7mv/? slope -40? to +125?-rated temperature range 20-pin thin qfn (5mm ? 5mm), 0.8mm height (max) max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics ________________________________________________________________ maxim integrated products 1 20 19 18 17 in- in+ shdn1 16 inp v cc 13 12 11 14 15 lx in inp pwm pgnd 4 3 2 1 tout agnd shdn2 aout 5 ref 6 7 8 9 agnd comp adj shdn3 10 out max1958/ max1959 top view thin qfn 5mm x 5mm pin configuration ordering information 19-2659; rev 0; 10/02 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 max1958 etp -40 c to +85 c 20 thin qfn-ep* max1959 etp -40 c to +85 c 20 thin qfn-ep rail-to-rail is a registered trademark of nippon motorola, ltd. typical operating circuit and functional diagram appear at end of data sheet. evaluation kit available * ep = exposed paddle.
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in, inp, out, adj, shdn1 , shdn2 , shdn3 , pwm, v cc to pgnd ...................................-0.3v to +6v agnd to pgnd .....................................................-0.3v to +0.3v comp, ref to agnd ....................................-0.3 to (v in + 0.3v) in+, in-, aout, tout to agnd ................-0.3 to (v vcc + 0.3v) lx current (note 1).............................................................1.6a output short-circuit duration.....................................continuous continuous power dissipation (t a = +70 c) 20-pin thin qfn 5mm x 5mm (derate 20.8mw/ c above +70 c) .............................1670mw operating temperature range ...........................-40 c to +85 c junction temperature ......................................................+150 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10s) .................................+300 c electrical characteristics (step-down converter) (v inp = v in = v vcc = v shdn1 = 3.6v, v pwm = v pgnd = v agnd = v shdn2 = v shdn3 = 0, v adj = 1.25v, comp = in- = in+ = aout = tout = unconnected, c ref = 0.1f, t a = 0 c to +85 c , v out for max1958 = 2.2v, v out for max1959 = 1.7v, unless otherwise noted. typical values are at t a = +25 c.) parameter conditions min typ max units supply voltage range 2.6 5.5 v undervoltage lockout threshold rising or falling, hysteresis is 1% 2.20 2.35 2.55 v max1958, pwm = agnd 190 300 max1959, pwm = agnd 280 450 a quiescent current v pwm = v in 3ma max1958 295 550 quiescent current in dropout max1959 330 600 a shutdown supply current v shdn1 = 0 0.1 6 a error amplifier v adj = 1.932v, i load = 0 to 600ma, v pwm = v in = 3.8v 3.38 3.40 3.42 v adj = 0.426v, i load = 0 to 30ma, v pwm = 0 0.739 0.750 0.761 out voltage accuracy (max1958) v adj = 0.426v, i load = 0 to 30ma, v pwm = v in = 4.2v 0.739 0.750 0.761 v v adj = 2.2v, i load = 0 to 600ma, v pwm = v in = 4v 3.58 3.60 3.62 v adj = 0.9v, i load = 0 to 30ma, v pwm = 0 0.985 1.00 1.015 out voltage accuracy (max1959) v adj = 0.9v, i load = 0 to 30ma, v pwm = v in = 4.2v 0.985 1.00 1.015 v v out = 0.75v 2 4 6 out input current (max1958) v out = 3.4v 11 17 25 a v out = 1v 2.5 4.0 6.5 out input current (max1959) v out = 3.6v 10 16 23 a adj input current (max1958) v adj = 0.426v to 1.932v -150 +1 +150 na adj input current (max1959) v adj = 0.9v to 2.2v -150 +1 +150 na positive comp output current (max1958) v adj = 1v, v out = 1.5v, v comp = 1.25v -27 -14 -7 a positive comp output current (max1959) v adj = 1v, v out = 1v, v comp = 1.25v -27 -14 -7 a note 1: lx has internal clamp diodes to pgnd and inp. applications that forward bias these diodes should take care not to exceed the ic s package power dissipation limits.
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics _______________________________________________________________________________________ 3 electrical characteristics (step-down converter) (continued) (v inp = v in = v vcc = v shdn1 = 3.6v, v pwm = v pgnd = v agnd = v shdn2 = v shdn3 = 0, v adj = 1.25v, comp = in- = in+ = aout = tout = unconnected, c ref = 0.1f, t a = 0 c to +85 c , v out for max1958 = 2.2v, v out for max1959 = 1.7v, unless otherwise noted. typical values are at t a = +25 c.) parameter conditions min typ max units negative comp output current (max1958) v adj = 1v, v out = 2v, v comp = 1.25v 7 14 27 a negative comp output current (max1959) v adj = 1v, v out = 1.4v, v comp = 1.25v 7 14 27 a reference ref output voltage 1.225 1.250 1.275 v ref load regulation 10a < i ref < 100a 2.50 6.25 mv undervoltage lockout threshold rising or falling, 1% hysteresis 0.85 1.00 1.10 v supply rejection 2.6v < v in < 5.5v 0.07 1.7 mv/v controller i lx = 180ma, v in = 3.6v 0.21 0.40 p-channel on-resistance i lx = 180ma, v in = 2.6v 0.25 0.5 ? i lx = 180ma, v in = 3.6v 0.18 0.30 n-channel on-resistance i lx = 180ma, v in = 2.6v 0.21 0.35 ? current-sense transresistance 0.5 v/a p-channel current-limit threshold 1.1 1.37 1.6 a p-channel pulse-skipping current threshold v pwm = 0 0.12 0.15 0.17 a n-channel current-limit threshold v pwm = v in -0.5 a n-channel zero-crossing comparator v pwm = 0 20 ma lx leakage current v in = 5.5v -20.0 +0.1 +20.0 a lx rms current (note 1) 1.0 a maximum duty cycle 100 % v pwm = 0 0 minimum duty cycle v pwm = v in = 4.2v 16 % oscillator frequency 0.85 1.00 1.15 mhz thermal-shutdown threshold hysteresis = +15 c 160 c logic inputs (pwm, shdn1 ) logic input high 2.6 v < v in < 5.5 v 1.6 v logic input low 2.6 v < v in < 5.5 v 0.6 v logic input current v in = 5.5v 0.1 1 a
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 4 _______________________________________________________________________________________ electrical characteristics (op amp) (v inp = v in = v vcc = v shdn2 = 2.7v, v aout = v vcc /2, r l = connected from aout to v vcc /2, v pgnd = v agnd = v shdn1 = v shdn3 = v pwm = v adj = 0, out = lx = tout = ref = comp = unconnected, v cm = 0, t a = 0 c to +85 c , unless otherwise noted. typical values are at t a = +25 c.) parameter conditions min typ max units supply voltage range 2.6 5.5 v v vcc = 2.6v 320 800 v vcc = 5v 375 900 supply current v shdn2 = 0, v vcc = 5.5v 0.1 2.0 a input offset voltage v agnd - 0.1v v cm v vcc + 0.1v 0.4 3.0 mv input bias current v agnd - 0.1v v cm v vcc + 0.1v 10 100 na input offset current v agnd - 0.1v v cm v vcc + 0.1v 1 10 na input resistance v in- - v in+ 10mv 4 m ? input common-mode voltage range, v cm -0.1 v vcc + 0.1 v common-mode rejection ratio, cmrr v agnd - 0.1v v cm v vcc + 0.1v 60 80 db power-supply rejection ratio, psrr 2.6v < v vcc < 5.5v 70 90 db v agnd + 0.05v v aout v vcc - 0.05v r l = 100k ? v aout v vcc - 0.20v r l = 2k ? 85 110 db r l = 100k ? 1 output voltage swing high, voh ? v vcc -v voh ? r l = 2k ? 35 90 mv r l = 100k ? 1 output voltage swing low, vol ? v vol - v agnd ? rl = 2k ? 30 90 mv sourcing, v vcc = 5v 11 output short-circuit current sinking, v vcc = 5v 30 ma shdn2 logic low 2.6v < v vcc < 5.5v 0.3 x v vcc v shdn2 logic high 2.6v < v vcc < 5.5v 0.7 x v vcc v shdn2 input current 0 < v shdn2 < v vcc 0.5 120 na gain bandwidth product, gbw 1 mhz phase margin, m 70 degrees gain margin, gm 20 db slew rate, sr 0.4 v/s input voltage noise density f = 10khz 52 nv/ hz hz
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics _______________________________________________________________________________________ 5 electrical characteristics (op amp) (continued) (v inp = v in = v vcc = v shdn2 = 2.7v, v aout = v vcc /2, r l = connected from aout to v vcc /2, v pgnd = v agnd = v shdn1 = v shdn3 = v pwm = v adj = 0, out = lx = tout = ref = comp = unconnected, v cm = 0, t a = 0 c to +85 c , unless otherwise noted. typical values are at t a = +25 c.) parameter conditions min typ max units power-on time 4s input capacitance 2.5 pf total harmonic distortion f =10khz, v aout = 2v p-p , avcl =1, v vcc = 5v, r aout = 100k ? to v vcc /2 0.01 % settling time to 0.01% ? v aout = 4v step, v vcc = 5v, avcl = 1 10 s active discharge output impedance v shdn2 = 0, i aout = 1ma 100 500 ? electrical characteristics (temperature sensor) (v inp = v in = v vcc = v shdn3 = 2.7v, v agnd = v pgnd = v pwm = v shdn1 = v shdn2 = v adj = 0, in- = in+ = aout = comp = lx = out = ref = unconnected, c tout = 0.01f (min), t a = 0 c to +85 c , unless otherwise noted. typical values are at t a = +25 c.) parameter conditions min typ max units t a = 0 c (note 2) -3.5 +3.5 t a = +25 c (note 2) -2.5 +2.5 temperature sensor error (note 3) t a = +85 c -2.5 +2.5 c output voltage at +27 c 1.56 v sensor gain (note 4) -11.64 mv/ c nonlinearity 0.4 % load regulation 0 i load 15a -5 mv line regulation 2.6v v vcc 5.5v -2.3 mv/v quiescent current 2.6v v vcc 5.5v 10 18 a shdn3 logic high voltage 2.6v < v vcc < 5.5v 1.6 v shdn3 logic low voltage 2.6v < v vcc < 5.5v 0.6 v shdn3 current v vcc = 5.5v 0.1 1.0 a
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 6 _______________________________________________________________________________________ electrical characteristics (step-down converter) (v inp = v in = v vcc = v shdn1 = 3.6v, v pwm = v pgnd = v agnd = v shdn2 = v shdn3 = 0, v adj = 1.25v, comp = in- = in+ = aout = tout = unconnected, c ref = 0.1f, t a = -40 c to +85 c , v out for max1958 = 2.2v, v out for max1959 = 1.7v, unless otherwise noted.) (note 5) parameter conditions min typ max units supply voltage range 2.6 5.5 v undervoltage lockout threshold rising or falling, hysteresis is 1% 2.20 2.55 v pwm = agnd (max1958) 300 quiescent current pwm = agnd (max1959) 450 a max1958 550 quiescent current in dropout max1959 600 a shutdown supply current v shdn1 = 0 6 a error amplifier v adj = 1.932v, i load = 0 to 600ma, v pwm = v in = 3.8v 3.36 3.44 v adj = 0.426v, i load = 0 to 30ma, v pwm = 0 0.739 0.761 out voltage accuracy (max1958) v adj = 0.426v, i load = 0 to 30ma, v pwm = v in = 4.2v 0.739 0.761 v v adj = 2.2v, i load = 0 to 600ma, v pwm = v in = 4v 3.570 3.625 v adj = 0.9v, i load = 0 to 30ma, v pwm = 0 0.98 1.02 out voltage accuracy (max1959) v adj = 0.9v, i load = 0 to 30ma, v pwm = v in = 4.2v 0.98 1.02 v v out = 0.75v 2 6 out input current (max1958) v out = 3.4v 11 25 a v out = 1v 2.5 6.5 out input current (max1959) v out = 3.6v 10.0 23.0 a adj input current (max1958) v adj = 0.426v to 1.932v -150 +150 na adj input current (max1959) v adj = 0.9v to 2.2v -150 +150 na positive comp output current (max1958) v adj = 1v, v out = 1.5v, v comp = 1.25v -27.0 -6.5 a positive comp output current (max1959) v adj = 1v, v out =1v, v comp = 1.25v -27.0 -6.5 a negative comp output current (max1958) v adj = 1v, v out = 2v, v comp = 1.25v 6.5 27.0 a negative comp output current (max1959) v adj = 1v, v out = 1.4v, v comp =1.25v 6.5 27.0 a reference ref output voltage 1.226 1.275 v ref load regulation 10a < i ref < 100a 6.25 mv undervoltage lockout threshold rising or falling, 1% hysteresis 0.85 1.10 v supply rejection 2.6v < v in < 5.5v 1.7 mv/v
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics _______________________________________________________________________________________ 7 electrical characteristics (step-down converter) (continued) (v inp = v in = v vcc = v shdn1 = 3.6v, v pwm = v pgnd = v agnd = v shdn2 = v shdn3 = 0, v adj = 1.25v, comp = in- = in+ = aout = tout = unconnected, c ref = 0.1f, t a = -40 c to +85 c , v out for max1958 = 2.2v, v out for max1959 = 1.7v, unless otherwise noted.) (note 5) parameter conditions min typ max units controller i lx = 180ma, v in = 3.6v 0.4 p-channel on-resistance i lx = 180ma, v in = 2.6v 0.5 ? i lx = 180ma, v in = 3.6v 0.3 n-channel on-resistance i lx = 180ma, v in = 2.6v 0.35 ? p-channel current-limit threshold 1.1 1.6 a p-channel pulse-skipping current threshold v pwm = 0 0.11 0.18 a lx leakage current v in = 5.5v -20 +20 a lx rms current (note 1) 1.0 a maximum duty cycle 100 % minimum duty cycle v pwm = 0 0 % oscillator frequency 0.8 1.2 mhz logic inputs (pwm, shdn1 ) logic input high 2.6v < v in < 5.5v 1.6 v logic input low 2.6v < v in < 5.5v 0.6 v logic input current v in = 5.5v 1 a
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 8 _______________________________________________________________________________________ electrical characteristics (op amp) (v inp = v in = v vcc = v shdn2 = 2.7v, v aout = v vcc /2, r l = connected from aout to v vcc /2, v pgnd = v agnd = v shdn1 = v shdn3 = v pwm = v adj = 0, out = lx = tout = ref = comp = unconnected, v cm = 0, t a = -40 c to +85 c , unless otherwise noted.) (note 5) parameter conditions min typ max units supply voltage range 2.6 5.5 v v vcc = 2.6v 800 v vcc = 5v 900 a supply current v shdn2 = 0, v vcc = 5.5v 2.0 input offset voltage v agnd - 0.1v v cm v vcc + 0.1v 3.0 mv input bias current v agnd - 0.1v v cm v vcc + 0.1v 100 na input offset current v agnd - 0.1v v cm v vcc + 0.1v 10 na input common-mode voltage range, v cm v agnd - 0.1v v vcc + 0.1v v common-mode rejection ratio, cmrr v agnd - 0.1v v cm v vcc + 0.1v 60 db power-supply rejection ratio, psrr 2.6v < v vcc < 5.5v 70 db large-signal voltage gain, avol v agnd + 0.20v v out v vcc - 0.20v, r l = 2k ? 85 db output voltage swing high, voh ? v vcc - v voh ? , r l = 2k ? 90 output voltage swing low, vol ? v vol - v agnd ? , rl = 2k ? 90 mv shdn2 logic low 2.6v < v vcc < 5.5v 0.3 x v vcc v shdn2 logic high 2.6v < v vcc < 5.5v 0.7 x v vcc v shdn2 input current 0 < v shdn2 < v vcc 120 na capacitive-load stability avcl = 1v/v (note 2) 470 pf active discharge output impedance v shdn2 = 0, i aout = 1ma 500 ?
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics _______________________________________________________________________________________ 9 electrical characteristics (temperature sensor) (v inp = v in = v vcc = v shdn3 = 2.7v, v agnd = v pgnd = v pwm = v shdn1 = v shdn2 = v adj = 0, in- = in+ = aout = comp = lx = out = ref = unconnected, c tout = 0.01f (min), t a = -40 c to +85 c , unless otherwise noted.) (note 5) parameter conditions min typ max units t a = -40 c (note 2) -7 +4 t a = +25 c (note 2) -2.5 +2.5 temperature sensor error (note 3) t a = +85 c -2.5 +2.5 c load regulation 0 i load 15a -5 mv line regulation 2.6v v vcc 5.5v -2.3 mv/v quiescent current 2.6v v vcc 5.5v 18 a shdn3 logic high voltage 2.6v < v vcc < 5.5v 1.6 v shdn3 logic low voltage 2.6v < v vcc < 5.5v 0.6 v shdn3 current v vcc = 5.5v 1 a note 2: guaranteed by design, not production tested. note 3: v tout = (-4 x 10 -6 ) ? (t 2 c) - (1.13 ? 10 -2 ) ? (t c) + 1.8708v. note 4: linearized gain = v tout = -11.64mv/ c + 1.8778v. note 5: specifications to -40 c are guaranteed by design and not subject to production test. typical operating characteristics (t a = +25 c, unless otherwise noted.) efficiency vs. load current max1958/59 toc01 load current (ma) efficiency (%) 100 65 70 75 80 85 90 95 100 60 10 1000 skip mode v in = 3.6v skip mode v in = 4.2v pwm v in = 3.6v pwm v in = 4.2v v out = 3.4v efficiency vs. load current max1958/59 toc02 load current (ma) efficiency (%) 100 40 50 60 70 80 90 100 30 10 1000 pwm v in = 3.6v pwm v in = 4.2v skip mode v in = 4.2v skip mode v in = 3.6v v out = 1.5v efficiency vs. load current max1958/59 toc03 load current (ma) efficiency (%) 100 50 60 70 80 90 100 40 10 1000 pwm v in = 3.6v pwm v in = 4.2v skip mode v in = 4.2v skip mode v in = 3.6v v out = 2.5v
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 10 ______________________________________________________________________________________ typical operating characteristics (continued) (t a = +25 c, unless otherwise noted.) 400ns/div heavy-load switching waveforms (i load = 600ma) i lx v out ac-coupled 5v/div 10mv/div max1958/59 toc07 lx 100ma/div 400ns/div medium-load switching waveforms (i load = 300ma) i lx v out ac-coupled 5v/div 10mv/div max1958/59 toc08 lx 100ma/div 400ns/div light-load switching waveforms (pwm = in, i load = 30ma) i lx v out ac-coupled 5v/div 10mv/div max1958/59 toc09 lx 100ma/div 400ms/div light-load switching waveforms (pwm = agnd, i load = 30ma) i lx v out ac-coupled 5v/div 10mv/div max1958/59 toc10 lx 100ma/div dropout voltage across p-channel mosfet vs. load current max1958/59 toc04 load current (ma) dropout voltage (mv) 700 600 500 400 300 200 100 50 100 150 200 250 300 0 0 800 supply current vs. input voltage skip mode max1958/59 toc05 input voltage (v) supply current ( a) 5.0 4.5 3.5 4.0 3.0 2.5 70 90 110 130 150 170 190 210 230 250 50 2.0 5.5 pwm = agnd v out = 1.5v max1958 supply current vs. input voltage forced pwm max1958/59 toc06 input voltage (v) supply current (ma) 5.0 4.5 4.0 3.5 3.0 2.5 1 2 3 4 5 6 0 2.0 5.5 v out = 0.75v pwm = in max1958
400 s/div entering and exiting shutdown i in v out 5v/div 1v/div max1958/59 toc11 v shdn 50ma/div 10 s/div max1958 adj transient v adj 3.4v 0.426v max1958/59 toc12 v out 1.932v 0.75v max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics ______________________________________________________________________________________ 11 100 s/div load transient pwm = agnd i out 30ma max1958/59 toc13 v out ac-coupled 400ma 100mv/div c out = 10 f 100 s/div load transient pwm = in i out 30ma max1958/59 toc14 v out ac-coupled 400ma 100mv/div c out = 10 f 1ms/div load transient v in 3v max1958/59 toc15 v out ac-coupled 4v 10mv/div typical operating characteristics (continued) (t a = +25 c, unless otherwise noted.) 200 300 250 400 350 450 500 2.0 3.5 4.0 2.5 3.0 4.5 5.0 5.5 op amp supply current vs. input voltage max1958/59 toc16 v cc (v) i cc ( a) t a = +125 c t a = +85 c t a = +25 c t a = -40 c
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 12 ______________________________________________________________________________________ typical operating characteristics (continued) (t a = +25 c, unless otherwise noted.) 0 -100 0.1 1 10 100 1k 10k op amp power-supply rejection ratio vs. frequency -80 max1958/59 toc22 frequency (hz) psrr (db) -60 -40 -20 -90 -70 -50 -30 -10 0 200 100 400 300 500 600 0 1.0 0.5 1.5 2.0 2.5 op amp input offset voltage vs. common-mode voltage max1958/59 toc17 v cm (v) v os ( v) v vcc = 2.5v t a = +125 c t a = +85 c t a = +25 c t a = -40 c 0 200 100 400 300 500 600 023 1 456 op amp input offset voltage vs. common-mode voltage max1958/59 toc18 v cm (v) v os ( v) v vcc = 5.5v t a = -40 c t a = +25 c t a = +85 c t a = +125 c -15 -5 -10 5 0 15 10 20 023 1 456 op amp input bias current vs. common-mode voltage max1958/59 toc19 v cm (v) i bias (na) t a = -40 c t a = +25 c t a = +125 c v vcc = 5.5v t a = +85 c 0 4 2 8 6 12 10 14 0 1.0 1.5 2.0 0.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 op amp output source current vs. output voltage max1958/59 toc20 v aout (v) i source (ma) v vcc = 5.5v v vcc = 2.5v 0 10 5 25 20 15 30 35 45 40 50 0 1.0 2.0 3.0 4.0 5.0 op amp output sink current vs. output voltage max1958/59 toc21 v aout (v) i sink (ma) v vcc = 2.5v v vcc = 5.5v 0.5 1.5 2.5 3.5 4.5 5.5
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics ______________________________________________________________________________________ 13 typical operating characteristics (continued) (t a = +25 c, unless otherwise noted.) 80 0.1 1 10 100 1k 10k 40 20 0 -20 -40 op amp gain and phase vs. frequency max1958/59 toc23 frequency (hz) gain (db) 60 90 -30 -90 -150 -210 -270 30 phase (degrees) phase gain 2k ? || 470pf 4 s/div op amp small-signal transient response (noninverting) in out 20mv/div 20mv/div max1958/59 toc24 4 s/div op amp small-signal transient response (inverting) in out 20mv/div 20mv/div max1958/59 toc25 40 s/div op amp large-signal transient response (noninverting) in out 2v/div 2v/div max1958/59 toc26 v vcc = 5v 40 s/div op amp large-signal transient response (inverting) in out 2v/div 2v/div max1958/59 toc27 v vcc = 5v temperature sensor tout voltage vs. temperature max1958/59 toc28 temperature ( c) tout (v) 110 95 50 65 80 -10 5 20 35 -25 0.75 1.25 1.75 2.25 0.25 -40 125
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 14 ______________________________________________________________________________________ typical operating characteristics (continued) (t a = +25 c, unless otherwise noted.) temperature sensor error vs. temperature max1958/59 toc29 temperature ( c) error ( c) 80 65 50 35 20 5 -10 -25 -1.0 -0.5 0 0.5 1.0 1.5 -1.5 -40 95 temperature sensor supply current vs. input voltage max1958/59 toc30 input voltage (v) supply current ( a) 5 4 123 4 2 6 8 10 14 12 16 18 20 0 06 pin description pin name function 1 aout op-amp output. aout discharges to agnd during shutdown. 2 shdn2 shutdown control input for the op amp. drive to agnd to shut down the op amp. connect to v cc or drive high for normal operation. 3 agnd analog ground. ground for op amp, temperature sensor, and the precision circuits in the dc-to-dc regulator. connect to pin 6. 4 tout analog voltage output representing the die temperature. bypass to agnd with a 0.01f capacitor. 5 ref internal 1.25v reference. bypass to agnd with a 0.1f capacitor. 6 agnd analog ground. connect to pin 3. 7 comp compensation. typically, connect a 22pf capacitor from comp to agnd and a 9.1k ? resistor and 560pf capacitor in series from comp to agnd to stabilize the regulator (see the compensation and stability section). 8 adj external reference input. connect adj to the output of a d/a converter for dynamic adjustment of the regulator s output voltage. out regulates at (1.76 x v adj ) for the max1958 and (2 x v adj - 0.8v) for the max1959. 9 shdn3 shutdown control input for the temperature sensor. drive to agnd to shut down the temperature sensor. connect to v cc or drive high for normal operation. 10 out output voltage feedback. connect out directly to the output. out is high impedance during shutdown. 11 pgnd power ground for the dc-to-dc converter 12 lx inductor connection to the internal power mosfets 13 in low-current supply voltage input. connect to inp at the ic.
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics ______________________________________________________________________________________ 15 pin description (continued) pin name function 14 inp high-current supply voltage input. connect to a 2.6v to 5.5v source. bypass to pgnd with a low- esr 4.7f capacitor. connect to pin 16. 15 pwm pwm/skip-mode input. drive low to use pwm mode at medium and heavy loads and pulse-skipping mode at light loads. drive high to force pwm mode at all loads. 16 inp supply voltage input. connect to pin 14. 17 shdn1 shutdown control input for the converter. drive to agnd to shut down the converter. connect to in or drive high for normal operation. 18 v cc supply input for op amp and temperature-sensor circuitry. connect to inp through an rc filter. 19 in+ noninverting input for the op amp 20 in- inverting input for the op amp exposed paddle connect to large agnd plane. internally connected to agnd. detailed description pwm step-down dc-to-dc converter the pwm step-down dc-to-dc converter is optimized for low-voltage, battery-powered applications where high efficiency and small size are priorities. it is specifically intended to power the linear hbt pa in n-cdma/ w-cdma handsets. an analog control signal (adj) dynamically adjusts the converter s output voltage from 0.75v to 3.4v (max1958) or 1v to 3.6v (max1959) with a settling time of approximately 30s. the max1958/ max1959 operate at a high 1mhz switching frequency that reduces external component size. the ic contains an internal synchronous rectifier that increases efficiency and eliminates the need for an external schottky diode. the normal operating mode uses constant-frequency pwm switching at medium and heavy loads and pulse skips at light loads to reduce supply current and extend battery life. an additional forced-pwm mode switches at a constant frequency, regardless of load, to provide a well-controlled noise spectrum for easier filtering in noise-sensitive applications. the max1958/max1959 are capable of 100% duty-cycle operation to increase efficiency in dropout. battery life is maximized with a 0.1a (typ) logic-controlled shutdown mode. normal-mode operation connecting pwm to gnd enables pwm/pulse-skipping operation. this proprietary control scheme uses pulse- skipping mode at light loads to improve efficiency and reduce quiescent current to 190a for the max1958 and 280a for the max1959. with pwm/pulse-skipping mode enabled, the max1958/max1959 initiate pulse- skipping operation when the peak inductor current drops below 150ma. during pulse-skipping operation, switching occurs only as necessary to service the load, thereby reducing the switching frequency and associat- ed losses in the internal switch, synchronous rectifier, and inductor. during pulse-skipping operation, a switching cycle initi- ates when the error amplifier senses that the output voltage has dropped below the regulation point. if the output voltage is low, the high-side p-channel mosfet switch turns on and conducts current through the inductor to the output filter capacitor and load. the pmos switch turns off when the output voltage rises above the regulation point and the error amplifier is sat- isfied. the max1958/max1959 then wait until the error amplifier senses an out-of-regulation output voltage to start the cycle again. at peak inductor currents above 150ma, the max1958/max1959 operate in pwm mode. during pwm operation, the output voltage is regulated by switching at a constant frequency and then modulating the power transferred to the load using the error com- parator. the error amplifier output, the main switch current-sense signal, and the slope compensation ramp are all summed at the pwm comparator (see the functional diagram ). the comparator modulates the output power by adjusting the peak inductor current during the first half of each cycle based on the output error voltage. the max1958/max1959 have relatively low ac loop gain coupled with a high-gain integrator to enable the use of a small, low-valued output filter capacitor. the resulting load regulation is 1.5% from 0
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 16 ______________________________________________________________________________________ to 600ma. some jitter is normal during the transition from pulse-skipping mode to pwm mode with loads around 75ma. this has no adverse impact on regulation. forced-pwm operation to force pwm operation at all loads, connect pwm to in. forced-pwm operation is desirable in sensitive rf and data-acquisition applications to ensure that switching-noise harmonics are predictable and can be easily filtered. this is to ensure that the switching noise does not interfere with sensitive if and data sampling frequencies. a minimum load is not required during forced-pwm operation because the synchronous recti- fier passes reverse inductor current as needed to allow constant-frequency operation with no load. forced- pwm operation has higher quiescent current than pulse-skipping mode (3ma typically compared to 190a) due to continuous switching. 100% duty-cycle operation the maximum on-time can exceed one internal oscillator cycle, which permits operation at 100% duty cycle. as the input voltage drops, 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 (typically 0.25 ? ) and the inductor resistance. near dropout, cycles may be skipped, reducing switching frequency. however, voltage ripple remains small because the current ripple is still low. dropout dropout occurs when the desired output regulation voltage is higher than the input voltage minus the voltage drops in the circuit. in this situation, the duty cycle is 100%, so the high-side p-channel mosfet is held on continuously and supplies current to the output up to the current limit. the output voltage in dropout falls to the input voltage minus the voltage drops. the largest voltage drops occur across the inductor and high-side mosfet. the dropout voltage increases as the load current increases. during dropout, the high-side, p-channel mosfet turns on and the controller enters a low-current con- sumption mode. every 6s (six cycles), the max1958/ max1959 check to see if the device is in dropout. the ic remains in this mode until it is no longer in dropout. comp clamp the max1958/max1959 compensation network has a 1v to 2.25v error-regulation range. the clamp opti- mizes transient response by preventing the voltage on comp from rising too high or falling too low. undervoltage lockout (uvlo) the dc-to-dc converter portion of the max1958/ max1959 is disabled if battery voltage on in is below the uvlo threshold of 2.35v (typ). lx remains high imped- ance until the supply voltage exceeds the uvlo thresh- old. this guarantees the integrity of the output voltage and prevents excessive current during startup and as the battery supply drops in voltage during use. the op amp and temperature sensor are not connected to the uvlo and therefore continue to operate normally. synchronous rectification an n-channel synchronous rectifier operates during the second half of each switching cycle (off-time). when the inductor current falls below the n-channel current-com- parator threshold or when the pwm reaches the end of the oscillator period, the synchronous rectifier turns off. this prevents reverse current flow from the output to the input in pulse-skipping mode. during pwm opera- tion, small amounts of reverse current flow through the n-channel mosfet during light loads. this allows reg- ulation with a constant switching frequency and elimi- nates minimum load requirements for fixed-frequency operation. the n-channel reverse-current comparator threshold is -500ma. the n-channel zero-crossing threshold in pulse-skipping mode is 20ma (see the forced-pwm operation and normal-mode operation sections) shutdown mode driving shdn1 to ground puts the dc-to-dc converter into shutdown mode. in shutdown mode, the reference, control circuitry, internal-switching mosfet, and syn- chronous rectifier turn off and the output (lx) becomes high impedance. input current falls to 0.1a (typ) dur- ing shutdown mode. drive shdn1 high for normal operation. thermal limit the thermal limit is set at approximately +160 c and shuts down only the converter. in this state, both main mosfets are turned off. once the ic cools by 15 c, the converter operates normally. a continuous overload condition results in a pulsed output. during thermal- limit conditions, the op amp and temperature sensor continue to operate. current-sense comparators the ic uses several internal current-sense comparators. in pwm operation, the current-sense amplifier, combined with the pwm comparator, sets the cycle-by-cycle cur- rent limit and provides improved load and line response. this allows tighter specification of the inductor-saturation current limit to reduce inductor cost. a second 150ma current-sense comparator monitors the current through
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics ______________________________________________________________________________________ 17 the p-channel switch and controls entry into pulse-skip- ping mode. a third current-sense comparator monitors current through the internal n-channel mosfet to pre- vent excessive reverse currents and determines when to turn off the synchronous rectifier. a fourth comparator used at the p-channel mosfet detects overcurrent. this protects the system, external components, and internal mosfets during overload conditions. rail-to-rail op amp the max1958/max1959 contain a rail-to-rail op amp that can be used to provide bias for the hbt pa. as the power needs of the pa change, the op amp can be used to dynamically change the bias point for the pa in order to optimize efficiency. rail-to-rail input stage the op amp in the max1958/max1959 has rail-to-rail input and output stages that are specifically designed for low-voltage, single-supply operation. the input stage consists of composite npn and pnp differential stages, which operate together to provide a common- mode range extending beyond both supply rails. the crossover region of these two pairs occurs halfway between vcl and agnd. the input offset voltage is typically 400v. the max1958/max1959 op amp inputs are protected from large differential input voltages by internal 5.3k ? series resistors and back-to-back triple-diode stacks across the inputs (figure 1). for differential input volt- ages much less than 2.1v (three diode drops), input resistance is typically 4m ? . for differential voltages greater than 2.1v, input resistance is around 10.6k ? , and the input bias current can be approximated by the following equation: in the region where the differential input voltage increases to about 2.1v, the input resistance decreases exponentially from 4m ? to 10.6k ? as the diodes begin to conduct. it follows that the bias current increases with the same curve. rail-to-rail output stage the max1958/max1959 op amp can drive down to a 2k ? load and still typically swing within 35mv of the supply rails. figure 2 shows the output voltage swing of the max1958 configured with a v = 1.57v/v and with v vcc at 4.2v. temperature sensor the max1958/max1959 analog temperature sensor s output voltage is a linear function of its die temperature. the slope of the output voltage is approximately -11.64mv/ c and there is a 1.878v offset at 0 c to allow measurement of positive temperatures. the tempera- ture sensor functions from -40 c to +125 c .the tem- perature error is less than 2.5 c at temperatures from +25 c to +85 c. nonlinearity the benefit of silicon analog temperature sensors over thermistors is the linearity over extended temperatures. the nonlinearity of the max1958/max1959 is typically 0.4% over the 0 c to +85 c temperature range. i vv k bias diff = (.) . -2 1 10 6 ? figure 1. input protection circuit v in+ 2v/div v aout 2v/div figure 2. op-amp output voltage swing
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 18 ______________________________________________________________________________________ transfer function the temperature-to-voltage transfer function has an approximately linear negative slope and can be described by the following equation: t is the die temperature in c. therefore: to account for the small amount of curvature in the transfer function, use the equation below to obtain a more accurate temperature reading: applications information pwm step-down dc-to-dc converter setting the output voltage the max1958/max1959 are optimized for highest sys- tem efficiency when applying power to a linear hbt pa in n-cdma/w-cdma handsets. the supply voltage to the pa is reduced (from 3.4v to as low as 0.75v for max1958) when transmitting at less than full power to greatly conserve supply current and extend battery life. the typical load profile for a w-cdma pa can be seen in figure 3. the max1958/max1959 dramatically reduce battery drain in these applications. the max1958 output voltage is dynamically adjustable from 0.75v to 3.4v and max1959 output voltage is dynamically adjustable from 1v to 3.6v using the adj input. the input voltage cannot be lower than the output voltage. v out can be adjusted during operation by dri- ving adj with an external dac. the output voltage for the max1958 is determined as: the output voltage for the max1959 is determined as: the max1958/max1959 output voltage responds to a full-scale change in voltage and current in approxi- mately 30s. compensation and stability the max1958/max1959 are externally compensated with a resistor and a capacitor (r c and c c , typical application circuit ) in series from comp to agnd. an additional capacitor (c f ) is required from comp to agnd. the capacitor, c c , integrates the current from the transimpedance amplifier, averaging output capacitor ripple. this sets the device speed for transient response and allows the use of small ceramic output capacitors because the phase-shifted capacitor ripple does not dis- turb the current-regulation loop. the resistor, r c , sets the proportional gain of the output error voltage by a factor of g m ? r c . increasing this resistor also increases the sen- sitivity of the control loop to output ripple. the series resistor and capacitor set a compensation zero that defines the system s transient response. the load creates a dynamic pole, shifting in frequency with changes in load. as the load decreases, the pole frequency decreases. system stability requires that the compensation zero must be placed to ensure adequate phase margin (at least 30 at unity gain). the following is a design procedure for the compensation network. select an appropriate converter bandwidth (f c ) to stabi- lize the system while maximizing transient response. this bandwidth should not exceed 1/10 of the switching frequency. calculate the compensation capacitor, c c , based on this bandwidth: resistors r1 and r2 are internal to the max1958/ max1959. for the max1958, use r1 = 95k ? and r2 = 125k ? as nominal values for calculations. for the max1959, use r1 = 125k ? and r2 = 125k ? as nominal values for calculations. i out(max) is the maximum out- put current, r cs = 0.5v/a, and g m = 250s. select the closest standard value c c that gives an acceptable bandwidth. calculate the equivalent load impedance, r l , by: calculate the compensation resistance (r c ) to cancel out the dominant pole created by the output load and the output capacitance: 1 2 1 2 = rc r c l out c c r v i l out out max = () c v ir g r rr f c out out max cs m c = ? ? ? ? ? ? ? ? ? ? ? ? + ? ? ? ? ? ? () 12 12 1 2 vvv out adj = 208 -. vv out adj = 176 . vttv tout = + + ()(.). -- -- 4 10 1 13 10 1 8708 62 2 t vv mv c tout = . ./ - - 1 878 11 64 v mv c tv tout = + ? 11 64 1 878 ..
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics ______________________________________________________________________________________ 19 solving for r c gives: calculate the high-frequency compensation pole to cancel the zero created by the output capacitor s equivalent series resistance (esr): solving for c f gives: use the calculated value for c f or 22pf, whichever is larger. inductor selection there are several parameters that must be examined when determining an optimum inductor value. input voltage, output voltage, load current, switching fre- quency, and lir. lir is the ratio of inductor current rip- ple to dc load current. a higher lir value allows for a smaller inductor, but results in higher losses and higher output ripple current. a good compromise between size, efficiency, and cost is an lir of 30%. once all the parameters are chosen, the inductor value is deter- mined as follows: where f s is the switching frequency (1mhz). choose a standard-value inductor close to the calculated value. the exact inductor value is not critical and can be adjust- ed in order to make trade-offs between size, cost, and efficiency. lower inductor values minimize size and cost, but they also increase the output ripple and reduce the efficiency due to higher peak currents. on the other hand, higher inductor values increase efficiency, but eventually resistive losses due to extra turns of wire exceed the benefit gained from lower ac current levels. for any area-restricted applications, find a low-core-loss inductor having the lowest possible dc resistance. ferrite cores are often the best choice. the inductor s saturation current rating must exceed the expected peak inductor current (i peak ). consult the inductor manufacturer for sat- uration current ratings. determine i peak as: input capacitor selection the input capacitor (c in ) reduces the current peaks drawn from the battery or input power source and reduces switching noise in the ic. the impedance of the input capacitor at the switching frequency should be less than that of the input source so that high- frequency switching currents are not required from the source. the input capacitor must meet the ripple current requirement (i rms ) imposed by the switching currents. nontantalum chemistries (ceramic, aluminum, or organ- ic) are preferred due to their resistance to power-up surge currents. i rms is calculated as follows: output capacitor selection the output capacitor is required to keep the output voltage ripple small and to ensure stability of the regu- lation control loop. the output capacitor must have low impedance at the switching frequency. an additional constraint on the output capacitor is load transients. if it is desired for the output voltage to swing from 0.75v to 3.4v in 30s, the output capacitor should be approxi- mately 4.7f or less. ceramic capacitors are recom- mended. the output ripple is approximately: see the compensation and stability section for a dis- cussion of the influence of output capacitance and esr on regulation control-loop stability. rail-to-rail op amp shutdown mode the max1958/max1959 op amp (figure 4) features a low-power shutdown mode. when shdn2 is pulled low, the supply current for the amplifier drops to 0.1a, the amplifier is disabled, and the output is actively dis- charged to agnd with an internal 100 ? switch. pulling shdn2 high enables the amplifier. due to the output leakage currents of three-state devices and the small internal pullup current for shdn2 , do not leave shdn2 unconnected. floating v lir i esr fc ripple load max s out = + ? ? ? ? ? ? () 1 2 i ivvv v rms load out in out in = () - ii lir i peak load max load max =+ ? ? ? ? ? ? () () 2 l vvv v f i lir out in out in s load max = () - () cf rc r esr out c = 1 2 1 2 = rc rc esr out c f r rc c c l out c =
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 20 ______________________________________________________________________________________ shdn2 may result in indeterminate logic levels, and could adversely affect op-amp operation. driving capacitive loads the max1958/max1959 op amp is unity-gain stable for capacitive loads up to 470pf. applications that require a greater capacitive drive capability should use an iso- lation resistor (r iso ) between the output and the capacitive load (figure 5). note that this alternative results in a loss of gain accuracy because r iso forms a voltage-divider with r load . power-supply bypass the power-supply voltage applied to v cc for the op amp and temperature sensor in the max1958/ max1959 circuit is filtered from inp. connect v cc to inp through an rc network (r2 and c7 in figure 4) to ensure a quiet power supply. temperature sensor the temperature sensor provides information about the max1958/max1959 die temperature. the voltage at tout (v tout ) is related to die temperature as follows: for stable operation, bypass tout to agnd with at least a 0.01f capacitor. temperature sensor error due to die self-heating when the 800ma converter and the op amp are both operated at heavy load while the temperature sensor is enabled, the indicated temperature at tout deviates several degrees from the actual ambient temperature due to die self-heating effects. at light loads, when die self-heating is low, tout tends to be a good approxi- mation of the ambient temperature. at heavier loads, the die self-heating is appreciable; tout gives a good approximation of the die temperature, which can be several degrees higher than the ambient temperature. sensing circuit board and ambient temperature temperature sensors like those found in the max1958/max1959 that sense their own die tempera- vttv tout = + + ()(.). -- -- 4 10 1 13 10 1 8708 62 2 30 600 300 3.4 3.0 1.0 0.4 0 0.0 pa supply current (ma) pa supply voltage (v) figure 3. typical w-cdma power amplifier load profile table 1. recommended inductors manufacturer part no. inductance ( h) dc resistance (m ? ) rated dc max current (ma) dimensions l x w x h (mm) 800ma application sumida cdrh3d16-4r7 4.7 80 900 3.8 x 3.8 x 1.8 toko 972as-4r7m = p5 4.7 220 960 4.6 x 4.6 x 1.2 700ma application sumida cmd4d11-4r7 4.7 166 750 3.5 x 5.3 x 1.2 toko 976as-4r7 = p5 4.7 320 740 3.6 x 3.6 x 1.2 400ma application murata lqh3c4r7m34 4.7 200 450 2.5 x 3.2 x 2 sumida cdrh2d11-4r7 4.7 170 500 3.2 x 3.2 x 1.2 300ma application murata lqh1c4r7m04 4.7 650 0.34 1.6 x 3.2 x 2 note: efficiency may vary depending upon the inductor s characteristics. consult the inductor manufacturer for saturation current ratings.
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics ______________________________________________________________________________________ 21 tures must be mounted on, or close to, the object whose temperature they are intended to measure. there is a good thermal path between the exposed paddle of the package and the ic die; therefore, the max1958/max1959 can accurately measure the temperature of the circuit board to which they are sol- dered. if the sensor is intended to measure the temper- ature of a heat-generating component on the circuit board, it should be mounted as close as possible to that component and should share supply and ground traces (if they are not noisy) with that component where possible. this maximizes the heat transfer from the component to the sensor. the thermal path between the plastic package and the die is not as good as the path through the exposed paddle, so the max1958/max1959, like all temperature sensors in plastic packages, are less sensitive to the temperature of the surrounding air than they are to the temperature of its exposed paddle. they can be suc- cessfully used to sense ambient temperature if the cir- cuit board is designed to track the ambient temperature. as with any ic, the wiring and circuits must be kept insulated and dry to avoid leakage and corrosion, especially if the part is operated at cold temperatures where condensation can occur. the junction-to-ambient thermal resistance ( ja ) is the parameter used to calculate the rise of a device junc- tion temperature (t j ) due to its power dissipation. the ja for the 20-pin qfn package is +50 c/w. for the max1958/max1959, use the following equation to calculate the rise in die temperature: the power dissipated by the dc-to-dc converter domi- nates in this equation. it is then reasonable to assume tt p p p j a ja d converter d opamp d tempsensor =+ + + () ()()( ) aout in- v ref hbt pa r7 12k ? r6 6.8k ? max1958/ max1959 offset in+ v cc shdn2 r2 20 ? c7 0.1 f v in 2.6v to 5.5v inp figure 4. op-amp configuration vv r r aout in =+ ? ? ? ? ? ? + 1 6 7 aout in- c load r7 r6 max1958/ max1959 r load r iso 100 ? figure 5. configuration for driving larger capacitive loads
max1958/max1959 w-cdma/n-cdma cellular phone hbt pa management ics 22 ______________________________________________________________________________________ that the rise in die temperature due to the converter is a good approximation of the total rise in die temperature. therefore: this equation assumes that the losses in the inductor are relatively small. for inductors with high dc resis- tance, inductor loss must be accounted for in the cal- culation. the temperature rise due to power dissipation by the converter can be quite significant. pc board layout and routing high switching frequencies and large peak currents make 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 cause instability or regulation errors. connect the inductor, input filter capacitor, and output filter capacitor as close together as possible and keep their traces short, direct, and wide. connect their ground pins at a single common node in a star ground configuration. keep noisy traces, such as those from the lx pin, away from the output feedback network. position the bypass capacitors as close as possible to their respective pins to minimize noise coupling. for optimum performance, place input and output capaci- tors as close to the device as possible. connect agnd and pgnd to the highest quality system ground. the max1958 evaluation kit illustrates an example pc board layout and routing scheme. optimize performance of the op amp by decreasing the amount of stray capacitance at the op amp s inputs and output. decrease stray capacitance by placing external components as close to the device as possible to minimize trace lengths and widths. tt p t v iv i j a ja d converter a ja in in out out + () =+ ? () () - max1958/ max1959 in pwm shdn1 lx pgnd out inp v cc shdn2 shdn3 adj aout in- tout comp ref agnd exposed paddle in+ dac offset v tout v ref v cc hbt pa v in 2.6v to 5.5v c1 4.7 f r2 20 ? c7 0.1 f c5 0.1 f c f 22pf c c 560pf c6 0.01 f r c 9.1k ? c2 4.7 f r7 12k ? r6 6.8k ? l1 4.7 h sumida cdrh3d16-4r7 typical operating circuit
max1958/max1959 ______________________________________________________________________________________ 23 w-cdma/n-cdma cellular phone hbt pa management ics active discharge temperature sensor agnd op amp reference comp clamp pwm control pwm comparator 1mhz oscillator slope compensation current sense error amplifier max1958/ max1959 ref comp adj shdn1 pwm in+ in- shdn2 agnd shdn3 lx pgnd out vcc aout tout in inp functional diagram chip information transistor count: 3704 process: bicmos
max1958/max1959 maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 24 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2002 maxim integrated products printed usa is a registered trademark of maxim integrated products. w-cdma/n-cdma cellular phone hbt pa management ics package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) qfn thin.eps d2 (nd-1) x e e d c pin # 1 i.d. (ne-1) x e e/2 e 0.08 c 0.10 c a a1 a3 detail a 0.15 c b 0.15 c a document control no. 21-0140 package outline 16, 20, 28, 32l, qfn thin, 5x5x0.8 mm proprietary information approval title: c rev. 2 1 e2/2 e2 0.10 m c a b pin # 1 i.d. b 0.35x45 l d/2 d2/2 l c l c e e l c c l k k l l 2 2 21-0140 rev. document control no. approval proprietary information title: common dimensions exposed pad variations 1. dimensioning & tolerancing conform to asme y14.5m-1994. 2. all dimensions are in millimeters. angles are in degrees. 3. n is the total number of terminals. 4. the terminal #1 identifier and terminal numbering convention shall conform to jesd 95-1 spp-012. details of terminal #1 identifier are optional, but must be located within the zone indicated. the terminal #1 identifier may be either a mold or marked feature. 5. dimension b applies to metallized terminal and is measured between 0.25 mm and 0.30 mm from terminal tip. 6. nd and ne refer to the number of terminals on each d and e side respectively. 7. depopulation is possible in a symmetrical fashion. 8. coplanarity applies to the exposed heat sink slug as well as the terminals. 9. drawing conforms to jedec mo220. notes: 10. warpage shall not exceed 0.10 mm. c package outline 16, 20, 28, 32l, qfn thin, 5x5x0.8 mm

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