general description the max1886 is a high-current operational transcon-ductance amplifier. the max1886 is ideal for driving the backplane of an active matrix, dot inversion thin film transistor (tft) liquid crystal display (lcd). the max1886? high >500ma peak-current drive capability provides fast response to pulsed load conditions. the max1886 is stable from 0.47? to an unlimited amount of output capacitance. the max1886 is available in the low-profile (1.1mm max) 5-pin thin sot23 package and fully specified over the -40? to +85? extended temperature range. applications notebook lcd panelsmonitor lcd panels features ? stable with 0.47f to unlimited amount of outputcapacitance ? over 500ma peak drive current ? excellent settling characteristics with capacitiveload ? +4.5v to +13v input supply ? 0.45ma quiescent current ? thermal fault protection ? thin sot23-5 package (1.1mm max) max1886 high-current vcom drive buffer ________________________________________________________________ maxim integrated products 1 gnd fb+ v cc 15 fb- out max1886 thin sot23-5 top view 234 pin configuration v o v ref fb+ fb- v cc outgnd max1886 typical operating circuit 19-2095; rev 0; 8/01 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. * requires a special solder temperature profile described in the absolute maximum ratings section. ordering information part temp. range pin- package top m ark MAX1886EZK -40 c to +85 c 5 thin sot23-5* adql downloaded from: http:///
max1886 high-current vcom drive buffer 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. note 1: the max1886 is 100% production tested at t a = +25 c. specifications over temperature are guaranteed by design. v cc to gnd ............................................................-0.3v to +14v fb-, fb+, out to gnd...............................-0.3v to (v cc + 0.3v) continuous power dissipation (t a = +70 c) 5-pin thin sot23 (derate 7.1mw c above +70 c) .....727mw operating temperature range ...........................-40 c to +85 c junction temperature ......................................................+150 c storage temperature range .............................-65 c to +150 c electrical characteristics(v cc = 10v, fb- = out, v fb+ = 5v, c out = 0.47?, t a = -40 c to +85 c, unless otherwise noted. typical values are at t a = +25 c.) (note 1) parameter symbol conditions min typ max units v cc input supply range v cc 4.5 13 v v cc supply current i cc 450 900 ? input offset voltage v os v fb+ = +5v, no load -5 5 mv input bias current i bias -100 100 na input offset current i os +1.2v < v cm < +8.8v -100 100 na common-mode input range v cm | v os | < 10mv over cmr 1.2 v cc - 1.2v v power-supply rejection ratio psrr +4.5v < v cc < +13v, v fb+ = +2.25v 70 common-mode rejection ratio cmrr +1.2v < v cm < +8.8v 70 db gain-bandwidth product gbw small signal 1/6 c l hz small signal (?mv overdrive) 0.3 transconductance g m large signal (?0mv overdrive) 10 s t a = -40 c to +85 c ?75 ?50 output current drive i out ?00mv overdrive,v out = 3v or 7v t a = 0 c to +85 c ?50 ma thermal shutdown 170 ? thermal shutdown hysteresis 15 ? supply voltage reference voltage 0.470.47 r l c l v x 1 5 2 3 4 max1886 figure 1. load transient test circuit this device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device can be exposed to during board level solder attach and rework. maxim recommends the use of the solder profiles recommended in the industry-standard specification, jedec 020a, paragraph 7.6, table 3 for ir/vpr and convection reflow processes. preheating, per this standard, is required. hand or wave soldering is not recommended. downloaded from: http:///
max1886 high-current vcom drive buffer _______________________________________________________________________________________ 3 -0.10 -0.06-0.08 -0.02-0.04 0.02 0 0.04 0.080.06 0.10 4678 5 9 10 11 13 12 14 input offset voltage deviation vs. supply voltage max1886 toc01 v cc (v) v os (mv) v cm = v cc /2 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 -40 -15 10 35 60 85 input offset voltage deviation vs. temperature max1886 toc02 temperature ( c) ? v os (mv) v cc = 10v v cm = v cc /2 0 1 2 3 4 5 6 -40 -20 -30 -100 10203040 transconductance vs. output current max1886 toc03 output current (ma) transconductance (s) t a = -40 c t a = +25 c t a = +85 c 0 0.20.1 0.50.4 0.3 0.6 4.5 8.5 10.5 6.5 12.5 supply current vs. supply voltage max1886 toc04 supply voltage (v) supply current (ma) +85 c +25 c -40 c 0 0.30.2 0.1 0.4 0.5 0.6 0.7 0.8 0.9 1.0 -40 10 -15 35 60 85 no-load supply current vs. temperature max1886 toc05 temperature ( c) supply current (ma) short-circuit waveforms max1886 toc07 i cc 500ma/div i out 500ma/div v cc 5v/div v out 5v/div 20ms/div load transient 10v max1886 toc06 i out 500ma/div v x 10v/div v out 200mv/div ac-coupled 4 s/div r l = 2.5 , c l = 100nf, figure 1 typical operating characteristics (v cc = 10v, c out = 1?, v cm = 5v, t a = +25 c, unless otherwise noted.) downloaded from: http:///
max1886 detailed description the max1886 operational transconductance amplifier(ota) provides high-current output that is ideal for dri- ving capacitive loads such as the backplane of a tft lcd panel. the positive feedback input, fb+, allows common-mode biasing to mid-supply, or other vcom voltage. the max1886 unity-gain bandwidth is gbw = g m /c out where g m is the amplifier s transconductance. transconductance is the ratio of the output current tothe input voltage. the gain of the amplifier is dependent upon the load. the max1886 requires only a small 0.47? ceramic output capacitor for stability. the band- width is inversely proportional to the output capacitor, so large capacitive loads improve stability; however, lower bandwidth decreases the buffer s transient response time. to improve the transient response times, the max1886 s transconductance increases as the output current increases (see typical operating characteristics ). applications information output filter capacitor the max1886 requires a minimum of 0.47? outputcapacitance placed close to out. to ensure buffer sta- bility, the output capacitor esr must be 50m or lower. ceramic capacitors are an excellent choice. input bypass capacitor the max1886 requires a 0.47? input bypass capacitor(c2) close to the v cc supply input (see figure 2). place the max1886 close to the preceding voltage regulatoroutput capacitor so that the max1886 shares the same capacitor (c1). minimize trace length and use wide high-current vcom drive buffer 4 _______________________________________________________________________________________ startup waveform without soft-start max1886 toc08 i cc 500ma/div v cc 10v/div v fb+ 5v/div v out 5v/div 5 s/div c out = 0.47 f supply capacitorcharging current startup waveforms with soft-start max1886 toc09 i cc 500ma/div v cc 10v/div v fb+ 5v/div v out 5v/div 500 s/div c out = 0.47 f typical operating characteristics (continued) (v cc = 10v, c out = 1?, v cm = 5v, t a = +25 c, unless otherwise noted.) pin name description 1 out output of buffer amplifier. requires a minimum 0.47? ceramic filter capacitor to gnd. place the capacitor close to out. 2 gnd ground 3v cc voltage-supply input. bypass to gnd with a 0.47? capacitor close to the pin. use the outputcapacitor of the preceding voltage regulator as the additional filter capacitor. 4 fb+ noninverting input to buffer amplifier 5 fb- inverting input to buffer amplifier. feedback must be taken from the output filter capacitor terminal. pin description downloaded from: http:///
traces between the voltage regulator output and themax1886 v cc input to reduce pc board parasitics (inductance, resistance, and capacitance), which cancause undesired ringing. voltage reference the reference voltage for the max1886 input can beproduced using the output of a linear regulator. the lin- ear regulator will reject the ripple voltage produced by the source drivers (see figure 2). the output of this lin- ear regulator can also be used for the gamma correc- tion reference voltage. chip information transistor count: 121process: bicmos max1886 high-current vcom drive buffer _______________________________________________________________________________________ 5 figure 2. typical tft lcd backplane drive circuit pc board parasitics linear regulator optional reference voltage circuit gamma correction reference voltage to lcdbackplane c20.47 f v in 0.47 f 1 5 2 3 4 source driver voltage switching regulator c1 max1886 downloaded from: http:///
max1886 high-current vcom drive buffer 6 _______________________________________________________________________________________ package information downloaded from: http:///
max1886 high-current vcom drive buffer 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 _____________________ 7 2001 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (continued) downloaded from: http:///
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