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general description the max1512 is a programmable vcom-adjustment solution for thin-film transistor (tft) liquid-crystal displays (lcds). the max1512 simplifies the labor-intensive vcom-adjustment process and replaces mechanical potentiometers, which significantly reduces labor costs, increases reliability, and enables automation. the max1512 attaches to an external resistive voltage- divider and sinks a programmable current to set the vcom voltage level. an internal 7-bit digital-to-analog converter (dac) controls the sink current. the dac is ratiometric relative to avdd and is guaranteed to be monotonic over all operating conditions. this vcom calibrator ic includes an eeprom to store the desired vcom voltage level. the eeprom can be programmed repeatedly, giving tft lcd manufacturers the flexibility to calibrate the display panel as many times as the manufacturing process requires. the ic features a single-wire interface between the lcd panel and the programming circuit. the single- wire interface delivers both programming power and dac-adjustment commands to minimize changes to panel connectors and production equipment. the max1512 is available in an 8-pin 3mm x 3mm tdfn package. a complete evaluation kit is available to sim- plify evaluation and production development. applications lcd panels notebook computers monitors lcd tvs features ? 7-bit adjustable sink-current output ? resistor-adjustable full-scale range ? guaranteed monotonic output over operating range ? single-wire adjustment and programming* ? eeprom stores vcom setting ? interface enable/disable control (ce) ? 2.6v to 3.6v logic supply-voltage operating range (v dd ) ? 4.5v to 20v analog supply-voltage range (v avdd ) ? v dd uvlo protection ? 8-pin 3mm x 3mm tdfn (0.8mm max) max1512 eeprom-programmable tft vcom calibrator ________________________________________________________________ maxim integrated products 1 ce ctl avdd r set out r2 r1 vcom set gnd v dd v dd avdd max1512 pin configuration ordering information 1 2 3 4 8 7 6 5 set ce ctl v dd gnd n.c. avdd out max1512 tdfn top view a "+" sign will replace the first pin indicator on lead-free packages. typical operating circuit 19-2911 rev 3; 8/06 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 MAX1512ETA -40? to +85? 8 tdfn 3mm x 3mm MAX1512ETA+ -40? to +85? 8 tdfn 3mm x 3mm evaluation kit available *patent pending. + denotes lead-free package.
max1512 eeprom-programmable tft vcom calibrator 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (circuit of figure 1, v dd = 3v, v avdd = 10v, v out = 5v, r set = 30.1k ? , t a = 0 c to +85 c , unless otherwise noted. typical values are at 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 dd , set, ce to gnd...............................................-0.3v to +4v out to gnd ...........................................................-0.3v to +14v avdd to gnd.........................................................-0.3v to +24v ctl to gnd ............................................................-0.3v to +16v continuous power dissipation (t a = +70?) ............................... 8-pin thin qfn 3mm x 3mm (derate 24.4mw/? above +70?).............................................................1951mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +160? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units sink-current adjustment set voltage resolution 7 bits set differential nonlinearity guaranteed monotonic -1 +1 lsb set zero-scale error -1 +1 +2 lsb set full-scale error -12 +12 lsb set current i set 120 ? to gnd, v avdd = 20v 10 200 set external resistance (note 2) r set to gnd, v avdd = 4.5v 2.25 45.00 k ? v set / v avdd voltage ratio dac full scale 0.05 v/v v set / v avdd factory-set voltage ratio 0.024 0.025 0.026 v/v v dd supply v dd supply range v dd 2.6 3.6 v ce = v dd 32 55 v dd supply current i dd ce = gnd 12 20 ? rising edge 2.2 2.5 2.7 v dd power-on reset threshold falling edge 2.1 2.4 2.6 v v dd power-on reset hysteresis 100 mv control and programming ce input low voltage 2.6v < v dd < 3.6v 0.4 v ce input high voltage 2.6v < v dd < 3.6v 1.6 v ce startup time (note 3) 1 ms ctl high voltage 2.6v < v dd < 3.6v 0.70 x v dd 0.82 x v dd v ctl float voltage 2.6v < v dd < 3.6v 0.40 x v dd 0.62 x v dd v ctl low voltage 2.6v < v dd < 3.6v 0.20 x v dd 0.32 x v dd v ctl rejected pulse width 20 ? ctl minimum pulse width 200 ? ctl minimum time between pulses 10 ? ctl = gnd -10 ctl input current ctl = v dd 10 ?
max1512 eeprom-programmable tft vcom calibrator _______________________________________________________________________________________ 3 electrical characteristics (v dd = 3v, v avdd = 10v, v out = 5v, r set = 30.1k ? , t a = -40 c to +85 c , unless otherwise noted.) (note 1) note 1: limits are 100% production tested at t a = +25 c. limits over the operating temperature range are guaranteed through correlation using standard quality control (sqc) methods. note 2: set external resistor range is verified at dac full scale. note 3: guaranteed by design. not production tested. electrical characteristics (continued) (circuit of figure 1, v dd = 3v, v avdd = 10v, v out = 5v, r set = 30.1k ? , t a = 0 c to +85 c , unless otherwise noted. typical values are at t a = +25 c.) (note 1) parameter symbol conditions min typ max units ctl eeprom program voltage v pp (note 3) 15.25 15.5 15.75 v output voltage out leakage current v dd = 2.1v 1 na out settling time to ?.5 lsb error band 20 ? v out voltage range v out v set + 0.5v 13 v avdd supply v avdd supply range v avdd 4.5 20.0 v v dd = 2.1v, v avdd = 20v 0.04 avdd operating current i avdd v avdd = 20v 10 20 ? parameter symbol conditions min typ max units sink-current adjustment set differential nonlinearity guaranteed monotonic -1 +1 lsb set zero-scale error -1 +2 lsb set full-scale error -12 +12 lsb set current i set 120 ? to gnd, v avdd = 20v 10 200 set external resistance (note 2) r set to gnd, v avdd = 4.5v 2.25 45.00 k ? v dd supply v dd supply range v dd 2.6 3.6 v ce = v dd 55 v dd supply current i dd ce = gnd 20 ? rising edge 2.2 2.7 v dd power-on reset threshold falling edge 2.1 2.6 v control and programming ce input low voltage 2.6v < v dd < 3.6v 0.4 v ce input high voltage 2.6v < v dd < 3.6v 1.6 v avdd supply v avdd supply range v avdd 4.5 20.0 v avdd operating current i avdd v avdd = 20v 20 ?
max1512 eeprom-programmable tft vcom calibrator 4 _______________________________________________________________________________________ typical operating characteristics (circuit of figure 1, v dd = 3v, v avdd = 10v, v out = 5v, r set = 24.9k ? , t a = +25 c, dac half scale, unless otherwise noted.) v dd supply current vs. temperature max1512 toc01 temperature ( c) v dd supply current ( a) 80 60 20 40 0 -20 31.6 31.8 32.0 32.2 32.4 32.6 32.8 33.0 33.2 31.4 -40 ce = v dd = 3v v dd supply current vs. v dd max1512 toc02 v dd (v) v dd supply current ( a) 3.4 3.2 2.4 2.6 2.8 3.0 5 10 15 20 25 30 35 40 0 2.2 3.6 rising falling ce = v dd i out vs. r set max1512 toc03 r set (k ? ) i out ( a) 100 10 1 1 10 100 1000 10,000 0.1 0.1 1000 v avdd = 20v v avdd = 4.5v v dd = v out = 3v i out sink-current error vs. v dd max1512 toc04 v dd (v) i out sink-current error (lsb) 3.4 3.2 3.0 2.8 2.825 2.830 2.835 2.840 2.845 2.850 2.855 2.820 2.6 3.6 i out sink-current error vs. v avdd max1512 toc05 v avdd (v) i out sink-current error (lsb) 18.5 16.5 14.5 12.5 10.5 8.5 6.5 2.75 2.80 2.85 2.90 2.95 3.00 3.05 2.70 4.5 i out sink-current error vs. v out max1512 toc06 v out (v) i out sink-current error (lsb) 1.5 1.0 0.5 2.835 0 2.0 2.840 2.830 i out sink-current error vs. temperature max1512 toc07 temperature ( c) i out sink-current error (lsb) 80 60 40 20 0 -20 2.8 2.9 3.0 2.7 -40
max1512 eeprom-programmable tft vcom calibrator _______________________________________________________________________________________ 5 typical operating characteristics (continued) (circuit of figure 1, v dd = 3v, v avdd = 10v, v out = 5v, r set = 24.9k ? , t a = +25 c, dac half scale, unless otherwise noted.) total unadjusted error vs. dac setting max1512 toc08 dac setting total unadjusted error (lsb) 112 96 80 64 48 32 16 1 2 3 4 5 6 7 0 0128 r set = 25k ? r set = 100k ? integral nonlinearity vs. dac setting max1512 toc09 dac setting integral non-linearity (lsb) 112 96 64 80 32 48 16 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -1.0 0128 r set = 100k ? r set = 25k ? differential nonlinearity vs. dac setting max1512 toc10 dac setting differential non-linearity (lsb) 112 96 64 80 32 48 16 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -1.0 0 128 avdd power-up response max1512 toc11 0 0 v avdd 10v/div 40 s/div v out 1v/div 0 v dd 2v/div c out = 100pf v dd power-up response max1512 toc12 0 4v 5v 40 s/div 10v 0 v dd 2v/div v out v avdd c out = 100pf single lsb step-up response max1512 toc13 0 v out 5mv/div 40 s/div v ctl 2v c out = 100pf single lsb step-down response max1512 toc14 0 v out 5mv/div 40 s/div v ctl 2v c out = 100pf
max1512 eeprom-programmable tft vcom calibrator 6 _______________________________________________________________________________________ detailed description the max1512 is a solid-state alternative to mechanical potentiometers used for adjusting the lcd backplane voltage (vcom) in tft lcd displays. the max1512 attaches to an external resistive voltage-divider and sinks a programmable current (i out ), which sets the vcom level (figure 1). an internal 7-bit dac controls the sink current and allows the user to increase or decrease the vcom level (figure 2). the dac is ratio- metric relative to avdd and is monotonic over all oper- ating conditions. the user can store the dac setting in an internal eeprom. on power-up, the eeprom pre- sets the dac to the last stored setting. the single-wire interface between the lcd panel and the programming circuit adjusts the dac, programs the eeprom, and provides programming power. the resistive voltage-divider and the avdd supply set the maximum value of vcom. the max1512 sinks cur- rent from the voltage-divider to reduce the vcom level. the external resistor r set sets the full-scale sink cur- rent and the minimum value of vcom. pin description pin name function 1 out adjustable sink-current output. out connects to the resistive voltage-divider between avdd and gnd that sets the vcom voltage. i out lowers the divider voltage by an adjustable amount. see the set pin description. 2 avdd high-voltage analog supply. connects to the panel source-driver supply rail. 3 n.c. no connect. not internally connected. 4 gnd ground 5v dd supply input. +2.6v to +3.6v input range. 6 ctl vcom adjustment and eeprom programming control. ctl sets the internal dac code and programs the eeprom. a pulse-control method is used to adjust the vcom level. see the vcom adjustment (ctl) section . to program the dac setting into the eeprom as the power-on default, drive ctl to the eeprom programming voltage using the correct timing and voltage ramp rates. see the eeprom programming (ctl) section . 7ce control interface enable. connect ce to v dd to enable the ctl input. connect ce to gnd to disable the ctl input and reduce the supply current. 8 set full-scale sink-current adjustment input. connect a resistor, r set , from set to gnd to set the full-scale adjustable sink current. the full-scale adjustable sink current is equal to: i out is equal to the current through r set . ce ctl avdd r set 25k ? out r2 245k ? r1 200k ? vcom 5v set gnd v dd v dd 3v avdd 10v max1512 figure 1. standard application circuit v r avdd set 20 ? ? ? ? ? ?
max1512 eeprom-programmable tft vcom calibrator _______________________________________________________________________________________ 7 setting the vcom adjustment range (r set ) the external resistive voltage-divider sets the maximum value of the vcom adjustment range. r set sets the full-scale sink current, i out , which determines the mini- mum value of the vcom adjustment range. large r set values increase resolution but decrease the vcom adjustment range. calculate r1, r2, and r set using the following procedure: 1) choose the maximum vcom level (v max ), the mini- mum vcom level (v min ), and the avdd supply voltage (v avdd ). 2) calculate the r1 / r2 ratio: 3) calculate the r1 / r set ratio: 4) choose r set according to the limits shown in the electrical characteristics section and calculate the values for r1 and r2. 5) the resulting resolution is: a complete design example is given below: 1) v max = 5v, v min = 3v, v avdd = 10v 4) if r set = 24.9k ? , then r1 = 200k ? and r2 = 200k ? 5) resolution = 15.75mv 3 1 20 53 5 8 ) r r set = () = - 2 1 2 10 5 1 ) r r ?= -1 re solution v = () max min -v 127 r r v v set max 1 20 ? () max min -v r r v v avdd max 1 2 1 ? - ce r ctl 7 7 ctl avdd r set out r2 r1 19r dac eeprom vcom set gnd v dd v dd avdd max1512 control interface figure 2. simplified functional diagram
max1512 translating existing potentiometer circuits existing vcom adjustment circuits using conventional mechanical potentiometers can be translated into max1512 circuits. figures 3 and 4 show two common adjustment circuits and their equivalent max1512 circuits. interface enable/disable (ce) the max1512 control interface can be disabled to reduce the v dd supply current. connect ce to gnd to reduce the typical supply current from 32? to 12?. connect ce to v dd to enable the control interface. eeprom-programmable tft vcom calibrator 8 _______________________________________________________________________________________ avdd r set r set = out r2 r1 r1 = ra r2 = rb + rc ra (rb + rc) 20 rb vcom set avdd max1512 rb ra vcom avdd rc mechanical potentiometer max1512 equivalent circuit figure 3. replacement of mechanical/potentiometer circuit avdd r set r set = out r2 r1 r1 = rd r2 = rf rd (rd + re + rf) 20 re vcom set avdd max1512 re rd vcom avdd rf mechanical potentiometer max1512 equivalent circuit figure 4. replacement of mechanical/potentiometer circuit
the programming circuit in figure 5 drives ce high to enable the ctl input when it is connected. when the programming circuit is not connected, ce is pulled low through resistor r ce , which disables the ctl input. the ctl input is relatively immune to noise and brief volt- age transients. it can be safely left continuously enabled if higher supply current is acceptable. vcom adjustment (ctl) pulse ctl low for more than 200? to increment the dac setting, which increases the out sink current and lowers the vcom level by 1 least-significant bit (lsb) (figure 6). similarly, pulse ctl high for more than 200? to decre- ment the dac setting, which decreases the out sink cur- rent and increases the vcom level by 1 lsb. max1512 eeprom-programmable tft vcom calibrator _______________________________________________________________________________________ 9 ce ctl gnd max1512 programming circuit r ce v dd figure 5. optional circuit to drive ce >1ms >200 s >200 s >200 s >10 s <20 s <20 s >200 s ctl high v dd /2 ctl low ctl dac setting ce / v dd vcom ctl enabled 64 65 64 63 undefined first count ignored short counts ignored vcom up vcom down figure 6. vcom adjustment
max1512 to avoid unintentional vcom adjustment, the max1512 is guaranteed to reject ctl pulses shorter than 20?. in addition, to avoid the possibility of a single false pulse caused by power-up sequencing between v dd and ctl, the very first pulse is ignored. eeprom programming (ctl) to program the eeprom, apply the eeprom program- ming waveform through the ctl interface (figure 7). the control interface delivers programming power and dac adjustment commands on the same wire. this single-wire approach minimizes the number of connec- tions from the programming circuit to the lcd panel. to apply the eeprom programming waveform, carefully ramp ctl from midscale (v dd / 2) to the programming voltage, v pp , in 7.5ms as shown in figure 7. if the ramp is generated digitally, use at least 45 steps to achieve the required 320mv ramp resolution. during the ramp time, vcom adjustment is disabled and the eeprom cells are biased in preparation for programming. after reaching v pp , hold ctl at v pp for 1ms. during the efprom program time, the eeprom stores the dac setting. next, drive ctl to ground in less than 1ms and hold for at least 200?. finally, drive ctl to v dd / 2 to complete the write cycle. the eeprom is factory set to half scale. follow the eeprom programming spec- ifications in table 1 to guarantee reliable eeprom pro- gramming. violating the specifications can damage the eeprom or affect data retention. a complete evaluation kit is available to simplify evalua- tion and production development. eeprom-programmable tft vcom calibrator 10 ______________________________________________________________________________________ table 1. eeprom programming specifications parameter symbol min typ max units ctl programming voltage v pp 15.25 15.5 15.75 v ctl programming ramp t1 7.0 7.5 8.0 ms eeprom program time t2 0.9 1.0 1.1 ms v pp fall time t3 10 1000 ? done hold time t4 200 ? 0 v pp ctl voltage time v dd / 2 t1 t2 t4 t3 figure 7. eeprom programming
applications information the vcom adjustment and the eeprom programming must be performed with an external programming cir- cuit. refer to the max1512 evaluation kit for a complete programming circuit solution. use a circuit similar to the conceptual diagram shown in figure 8 to drive ctl. the accuracy of the programming voltage (v pp ) is critical for proper max1512 data reten- tion. the use of a comparator is recommended to verify the correct programming voltage has been reached. a complete design example of a ctl programming circuit is presented in the max1512 evaluation kit data sheet. electrostatic discharge (ctl, ce) often, ctl and ce are exposed at the panel connector and are therefore subject to electrostatic discharge (esd). resistor-capacitor (rc) filters can be employed at these inputs to improve their esd performance ( figure 9). if the ce panel connector is to be left floating after pro- gramming, be sure to include a resistor to ground (r ce ) to ensure a valid logic-low on ce. the time constant for a ce filter is not critical but the driving resistor must have a much lower resistance than rce to properly drive ce. if a filter is used at the ctl panel connector, its rc time- constant should be short enough to avoid interfering with ctl pulses or eeprom programming timing. a time constant less than 200? does not interfere with eep- rom programming. to avoid interfering with ctl puls- es, make the time constant small compared to the ctl pulsewidth used. leakage current (ctl) the ctl pin is internally biased to v dd / 2, but it is sen- sitive to leakage currents above 0.1?. when ctl is not driven, avoid leakage currents around the ctl pin. otherwise, reinforce the v dd / 2 set point with an exter- nal resistive voltage-divider. layout information use the following guidelines for good layout: place the vcom buffer and the r1/r2 voltage- divider close to the out pin (figure 1). keep the vcom buffer and the r1/r2 voltage-divider close to each other. place r set close to set. in noisy environments, bypass capacitors may be desired on v dd and/or v avdd . keep any bypass capacitors close to the ic with short connections to the pins. refer to the max1512 evaluation kit for an example of proper board layout. max1512 eeprom-programmable tft vcom calibrator ______________________________________________________________________________________ 11 dac 0 to 2.5v c user interface ctl max1512 ref 0 to 15.5v v pp verify figure 8. conceptual programming circuit v dd gnd ctl ce 1k ? r ce 100k ? 0.1 f 0.1 f v dd during programming, floating after programing floating after programming 10k ? max1512 figure 9. improved eos/surge performance
max1512 eeprom-programmable tft vcom calibrator 12 ______________________________________________________________________________________ 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 .) 6, 8, &10l, dfn thin.eps h 1 2 21-0137 package outline, 6,8,10 & 14l, tdfn, exposed pad, 3x3x0.80 mm
max1512 eeprom-programmable tft vcom calibrator 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. 13 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2006 maxim integrated products is a registered trademark of maxim integrated products, inc. 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 .) revision history pages changes at rev 3: 1, 11, 12 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 n d2 e2 e jedec spec b [(n/2)-1] x e package variations 0.25 min. k a2 0.20 ref. 2.300.10 1.500.10 6 t633-1 0.95 bsc mo229 / weea 1.90 ref 0.400.05 1.95 ref 0.300.05 0.65 bsc 2.300.10 8 t833-1 2.00 ref 0.250.05 0.50 bsc 2.300.10 10 t1033-1 2.40 ref 0.200.05 - - - - 0.40 bsc 1.700.10 2.300.10 14 t1433-1 1.500.10 1.500.10 mo229 / weec mo229 / weed-3 0.40 bsc - - - - 0.200.05 2.40 ref t1433-2 14 2.300.10 1.700.10 t633-2 6 1.500.10 2.300.10 0.95 bsc mo229 / weea 0.400.05 1.90 ref t833-2 8 1.500.10 2.300.10 0.65 bsc m o229 / weec 0.300.05 1.95 ref t833-3 8 1.500.10 2.300.10 0.65 bsc m o229 / weec 0.300.05 1.95 ref -drawing not to scale- h 2 2 21-0137 package outline, 6,8,10 & 14l, tdfn, exposed pad, 3x3x0.80 mm 2.300.10 mo229 / weed-3 2.00 ref 0.250.05 0.50 bsc 1.500.10 10 t1033-2

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