general description the MAX4473 pa power control ic is intended for closed-loop bias control of gsm power amplifiers. the device facilitates accurate control of the current deliv- ered to the power amplifier (pa) through a control volt- age. the error amplifier senses the voltage drop across an external current-sense resistor placed between the supply and the pa. the output of the error amplifier adjusts the pa gain until the current is proportional to the power control voltage applied to the MAX4473. this unique topology is useful in time-division-multiple- access (tdma) systems, such as gsm, where accurate transmit burst shaping and power control is required. user-selectable current sensing and gain setting resis- tors maximize flexibility. the MAX4473 operates from a single 2.7v to 6.5v sup- ply and typically draws 1.2ma of supply current. the error amplifier has a common-mode range that extends from 1v to v cc . the power control input and error amplifier outputs swing rail-to-rail . a low-power shut- down mode reduces supply current to less than 1? and activates an on-board active pull-down at the error amplifier output. fast enable/disable times of 0.9? reduce average power consumption without compro- mising dynamic performance. the MAX4473 is avail- able in a space-saving 8-pin qfn package. applications gsm cellular phones cordless phones precision current control high-frequency servo loops features optimized for gsm timing requirements 2.7v to 6.5v single-supply operation 1.2ma supply current 1? supply current in shutdown mode guaranteed 1.5? enable/disable times active output pull-down in shutdown mode rail-to-rail error amplifier output rail-to-rail power control input output drive capability?00 ? and 300pf loads 1v to v cc current sense input common-mode voltage range no phase-reversal for common-mode voltage from 0 to v cc external current sensing and gain setting resistors maximize flexibility available in a space-saving 8-pin qfn MAX4473 low-cost, low-voltage, pa power control amplifier for gsm applications in 8-pin qfn ________________________________________________________________ maxim integrated products 1 gnd pc 0.1 f 8 7 r 3r a3 pa gc in rfin 4 3 shdn buffer 5 6 a2 q1 a1 12 sr1 sr2 sr3 rg3 out v-to-i converter error amplifier v cc v cc v cc r sense rg1 rg2 i ccpa MAX4473 4 rg3 r sense v pc rg1 i ccpa = typical operating circuit 19-1448; rev 3; 8/02 pin configuration appears at end of data sheet. ordering information rail-to-rail is a registered trademark of nippon motorola, ltd. 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 MAX4473eua -40 c to +85 c 8 max MAX4473eta -40 c to +85 c 8 qfn MAX4473esa -40 c to +85 c 8 so
MAX4473 low-cost, low-voltage, pa power control amplifier for gsm applications in 8-pin qfn 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = 2.7v to 6.5v, shdn > 2.4v, MAX4473 test circuit, rg1 = rg2 = 1k ? 1%, rg3 = 2.5k ? 1%, r sense = 100 ? 1%, r l = 10k ? , c l = 300pf, t a = t min to t max , unless otherwise noted. typical values are at v cc = 6.0v, v pc = 1.0v, t a = +25 c.) (note 1) 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. v cc to gnd..............................................................................7v sr1, sr2, sr3, pc, shdn , out to gnd ............................................-0.3v to (v cc + 0.3v) sr1 to sr3......................................................................0 to v cc out and sr3 short-circuit duration to v cc or gnd ........................................................continuous current into any pin..........................................................50ma continuous power dissipation (t a = +70 c) 8-pin max (derate 4.10mw/ c above +70 c) ............330mw 8-pin qfn (derate 24.4mw/ c above +70 c) ............1951mw 8-pin so (derate 5.88mw/ c above +70 c).................471mw 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 v out = v cc / 2 r l = 500 ? to v cc / 2 v pc = 0 2.7v < v cc < 6.5v, v pc = gnd 1v < v sr1 , v sr2 < v cc , v pc = gnd inferred from cmrr test; v pc = gnd (note 2) 1v < v sr1 , v sr2 < v cc shdn < 0.4v, v sr1 = v sr2 = v cc 1v < v sr1 , v sr2 < v cc shdn < 0.4v, r l = 10k ? 1v < v sr1 , v sr2 < v cc , v pc = gnd, sr3 = unconnected shdn = 0 to v cc 1v < v sr1 , v sr2 < v cc , v pc = gnd, sr3 = unconnected conditions ma 20 output current limit 0.15 v cc - 0.15 80 120 80 130 80 125 db 80 130 db 80 90 power-supply rejection ratio 75 95 65 85 common-mode rejection ratio a 0.001 0.5 sr1, sr2 shutdown leakage current a 0.001 0.2 sr1, sr2 input bias offset current a 0.04 1 sr1, sr2 input bias current ma 1.2 2 supply current v 2.7 6.5 supply voltage v 1v cc sr1, sr2 input common-mode voltage range v/ c 10 sr1, sr2 input offset voltage drift 0.5 2 a 0.03 1 shutdown supply current v 2.4 shdn input high voltage v 0.4 shdn input low voltage a 0.5 shdn input current units min typ max parameter v cc = 2.7v v cc = 6.5v v cc = 6.5v, 0.3v < v out < 6v v cc = 2.7v, 0.3v < v out < 2.4v r l = 10k ? to v cc / 2 v cc = 6.5v, 0.7v < v out < 5.5v v cc = 2.7v, 0.7v < v out < 2.2v r l = 10k ? , c l = 300pf r l = 10k ? , c l = 300pf, f o = 10khz degrees 60 phase margin mhz 2 gain-bandwidth product measured from 30% to 70% of v out , r l = 10k ? , c l = 300pf v/s 1.8 slew rate large-signal gain r l = 10k ? to v cc / 2 r l = 500 ? to v cc / 2 v 0.5 v cc - 0.5 output voltage swing db 1v < v sr1 , v sr2 < v cc at +25 c mv 0.5 1 sr1, sr2 input offset voltage general error amplifier
MAX4473 low-cost, low-voltage, pa power control amplifier for gsm applications in 8-pin qfn _______________________________________________________________________________________ 3 electrical characteristics (continued) (v cc = 2.7v to 6.5v, shdn > 2.4v, MAX4473 test circuit, rg1 = rg2 = 1k ? 1%, rg3 = 2.5k ? 1%, r sense = 100 ? 1%, r l = 10k ? , c l = 300pf, t a = t min to t max , unless otherwise noted. typical values are at v cc = 6.0v, v pc = 1.0v, t a = +25 c.) (note 1) note 1: limits over temperature are guaranteed by design. note 2: no output phase-reversal for input common-mode voltage range from gnd to v cc . common-mode range limited by voltage drop across q1 and rg3. note 3: guaranteed by design. note 4: error dependent on tolerance of rg1, rg2, and rg3. specified with 0.1% tolerance resistors. v pc = 2.55v, sr1 = sr2 = v cc gnd < v pc < v cc - 0.15v no sustained oscillations (note 3) measure voltage across rg1, 0.3v < v pc < 2.55v (note 4) bandwidth from v pc to v rg1 conditions ma 0.750 4 sr3 output current limit a 0.04 1 pf 0 300 capacitive-load stability pc input bias current v/v 0.095 0.1 0.105 v pc to v rg1 ratio mhz 2 pc input bandwidth units min typ max parameter typical operating characteristics (see test circuit , t a = +25 c, unless otherwise noted.) 0.4 0.6 1.0 0.8 1.2 1.4 2.5 3.5 4.0 3.0 4.5 5.0 5.5 6.0 6.5 supply current vs. supply voltage MAX4473 toc01 supply voltage (v) supply current (ma) t a = -40 c t a = +25 c t a = +85 c shdn = v cc pc = gnd 0.0900 0.0925 0.0950 0.0975 0.1000 0.1025 0.1050 0.1075 0.1100 02 1 3456 v rg1 / v pc ratio vs. v pc response MAX4473 toc02 v pc (v) v rg1 / v pc (v/v) v cc = 6.0v 70 0 -30 10 100 1k 10k 100k 1m 10m error-amplifier response -10 0 -20 MAX4473 toc03 frequency (hz) gain (db) phase (degrees) 10 20 30 40 50 60 -180 -144 -126 -162 -108 -90 -72 -54 -36 -18 phase gain a vcl = 1000 v cc = 6.5v v cm = v cc / 2 v pc = 0 100k ? error amplifier 100 ? 10k ? 300pf out 500mv/div shdn 2v/div enable/disable time MAX4473 toc04 500ns/div v cc = 6.5v v pc = 2v gnd gnd 0 0.10 0.05 0.20 0.15 0.25 0.30 -40 10 -15 35 60 85 error-amplifier output low voltage vs. temperature MAX4473 toc05 temperature ( c) v ol (v) v cc = 6.5v, r l = 10k ? to v cc / 2 v cc = 2.7v, r l = 10k ? to v cc / 2 v cc = 6.5v, r l = 500 ? to v cc / 2 v cc = 2.7v, r l = 500 ? to v cc / 2 0.15 0.10 0.05 0 0.25 0.20 0.35 0.30 0.40 0.45 -40 10 -15 35 60 85 error-amplifier output high voltage vs. temperature MAX4473 toc06 temperature ( c) v cc - v oh (v) v cc = 2.7v, r l = 10k ? to v cc / 2 v cc = 6.5v, r l = 500 ? to v cc / 2 v cc = 6.5v, r l = 10k ? to v cc / 2 v cc = 2.7v, r l = 500 ? to v cc / 2 from 50% of shdn edge to v out = 1v, v pc = 2v s 0.9 1.5 enable/disable time gain control buffer and v-to-i converter
detailed description the MAX4473 is a voltage-controlled, unidirectional, high-side current setting amplifier for applications where accurate control of pa supply current is desired. this device is intended for wireless tdma based sys- tems (gsm, dect), where tight restrictions over the pa s transmit burst and output power require closed- loop control over the pa s output power. when used with a pa, the MAX4473 functions as a voltage-con- trolled constant current source, accurately setting pa supply current by varying the gain of the pa. if you know the output power versus supply current profile for the pa, you can set the pa s output power by control- ling the amount of supply current delivered to the pa. the MAX4473 is composed of an input buffer (a1), a voltage-to-current converting amplifier (a2), and a rail- to-rail output error amplifier (a3) (see typical operating circuit ). external gain and sense resistors allow pro- grammability for a wide range of applications. in the typical operating circuit , pa supply current flows from the system supply, through the external cur- rent-sense resistor (r sense ), to the pa. the rail-to-rail outputs of the error amplifier, a3, adjust the gain of the pa until the voltage drop across r sense equals the voltage drop across external gain resistor, rg1. the voltage drop across rg1 sets the voltage drop across r sense , with a larger voltage drop resulting in more current delivered to the pa. the voltage drop across rg1 is set by a1, a2, and the v-to-i fet, q1. a voltage applied to the pc input of the input buffer is divided by four by a resistor-divider network. a2 forces its inverting input and the source of q1 to v pc / 4, thus setting a voltage across rg3. the resulting current through rg3 sets the current through rg1. this unique architecture allows the supply current to be set independent of sup- ply voltage. set pa supply current according to the fol- lowing equation: i ccpa = ( v pc rg1 ) / ( 4 r sense rg3 ) shutdown mode when shdn is a logic-level low ( shdn < 0.4v), ampli- fiers a1, a2, and a3 are off, q1 is turned off, and the output of a3 is actively pulled to ground with an n- channel fet. supply current is reduced to less than 1a in shutdown mode. typical power-up time is 0.9s and typical power-down time is 0.3s, using the MAX4473 test circuit. applications information gain resistor selection (rg1, rg2, rg3) for proper operation, do not make the value of external gain resistors rg1 and rg2 larger than twice the value of rg3. in most practical applications, choose rg1 smaller than rg3 to limit the voltage drop over rg1 and r sense . a large voltage drop over r sense sub- stantially reduces the voltage applied to the pa, thus reducing pa output power. set rg2 equal to rg1 to compensate for the input bias currents of a3. recommended values for rg3 are between 1k ? and 10k ? . MAX4473 low-cost, low-voltage, pa power control amplifier for gsm applications in 8-pin qfn 4 _______________________________________________________________________________________ name function 1 sr1 inverting input of error amplifier and drain of v-to-i fet, q1. connect to supply side of current-sense resis- tor, r sense , through gain resistor rg1. 2 sr2 noninverting input of error amplifier. connect to load side of current-sense resistor, r sense , through gain resistor rg2. set rg2 equal to rg1. pin 3 shdn shutdown input. drive shdn low to disable all amplifiers, pull out to gnd, set the gate-to-source voltage of the v-to-i fet (q1) to 0, and reduce supply current to less than 1a. drive high or connect to v cc for nor- mal operation. 4 pc power control input. apply a voltage to pc to set a dc current through the sense resistor to control pa bias. 8 v cc +2.7v to +6.5v voltage supply input. bypass to ground with a 0.1f capacitor. 7 out output of error amplifier. connect to gain control pin of power amplifier in bias control applications. 6 sr3 inverting input of v-to-i converter and source of v-to-i fet, q1. connect to ground through gain resistor rg3. 5 gnd ground pin description
sense resistor selection (r sense ) choose r sense based on the following criteria: ? voltage loss: a high r sense value causes the power-source voltage to degrade through ir loss. for minimal voltage loss, use low r sense values. ? accuracy: a high r sense value allows lower cur- rents to be measured more accurately because input offset voltages become less significant when the sense voltage is larger. for best performance, select r sense to provide approximately 100mv of sense voltage for the full-scale current in each application. ? efficiency and power dissipation: at high current levels, the i 2 r losses in r sense are significant. take this into consideration when choosing the resistor value and its power dissipation (wattage) rating. also, the sense resistor s value may drift if it is allowed to heat up excessively. MAX4473 low-cost, low-voltage, pa power control amplifier for gsm applications in 8-pin qfn _______________________________________________________________________________________ 5 _________________________test circuit 2n3904 sr1 gnd r sense sr2 out sr3 pc shdn v cc v cc c l 300pf r l 10k ? rg1 1k ? 1% rg2 1k ? 1% rg3 2.5k ? 1% 100 ? 0.1% 0.1 f MAX4473 r e 750 ? pin configuration sr3 gnd pc 1 2 8 7 v cc out sr2 sr1 qfn/ max/so top view 3 4 6 5 MAX4473 shdn chip information transistor count: 348
6 _________________________________________________________________________________________ MAX4473 low-cost, low-voltage, pa power control amplifier for gsm applications in 8-pin qfn 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 .) soicn .eps package outline, .150" soic 1 1 21-0041 b rev. document control no. approval proprietary information title: top view front view max 0.010 0.069 0.019 0.157 0.010 inches 0.150 0.007 e c dim 0.014 0.004 b a1 min 0.053 a 0.19 3.80 4.00 0.25 millimeters 0.10 0.35 1.35 min 0.49 0.25 max 1.75 0.050 0.016 l 0.40 1.27 0.394 0.386 d d min dim d inches max 9.80 10.00 millimeters min max 16 ac 0.337 0.344 ab 8.75 8.55 14 0.189 0.197 aa 5.00 4.80 8 n ms012 n side view h 0.244 0.228 5.80 6.20 e 0.050 bsc 1.27 bsc c h e e b a1 a d 0 -8 l 1 variations: 8lumaxd.eps package outline, 8l umax/usop 1 1 21-0036 j rev. document control no. approval proprietary information title: max 0.043 0.006 0.014 0.120 0.120 0.198 0.026 0.007 0.037 0.0207 bsc 0.0256 bsc a2 a1 c e b a l front view side view e h 0.60.1 0.60.1 ? 0.500.1 1 top view d 8 a2 0.030 bottom view 1 6 s b l h e d e c 0 0.010 0.116 0.116 0.188 0.016 0.005 8 4x s inches - a1 a min 0.002 0.95 0.75 0.5250 bsc 0.25 0.36 2.95 3.05 2.95 3.05 4.78 0.41 0.65 bsc 5.03 0.66 6 0 0.13 0.18 max min millimeters - 1.10 0.05 0.15 dim
MAX4473 low-cost, low-voltage, pa power control amplifier for gsm applications in 8-pin qfn package information (continued) (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 .) 6, 8, &10l, qfn thin.eps package outline, 6, 8 & 10l, qfn thin (dual), exposed pad, 3x3x0.80 mm 21-0137 c common dimensions symbol min. max. a 0.70 0.80 d 2.90 3.10 e 2.90 3.10 a1 0.00 0.05 l 0.20 0.40 pkg. code 6 n t633-1 1.500.10 d2 2.300.10 e2 0.95 bsc e mo229 / weea jedec spec 0.400.05 b 1.90 ref [(n/2)-1] x e 1.500.10 mo229 / weec 1.95 ref 0.300.05 0.65 bsc 2.300.10 t833-1 8 package variations 21-0137 package outline, 6, 8 & 10l, qfn thin (dual), exposed pad, 3x3x0.80 mm c 0.250.05 2.00 ref mo229 / weed-3 0.50 bsc 1.500.10 2.300.10 10 t1033-1 0.25 min k a2 0.20 ref. 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ______________________ 7 ? 2002 maxim integrated products printed usa is a registered trademark of maxim integrated products.
|
