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buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 1 post office box 655303 ? dallas, texas 75265 10 gamma correction channels with >10 ma output current 1 v com buffer with >30 ma output current low power buffer ...i dd < 5 ma unity gain buffers capable of driving large capacitive loads input ranges matched to lcd reference requirements buffer1 drives 10 ma within 100 mv of v dd buffer10 drives 10 ma within 100 mv of gnd specified for 0 c to 85 c . . . 4.5 v to 16 v 1 pa input bias current description the buf11702 is a 10+1-channel buffer targeted toward the needs of modern high resolution lcd panels. these high resolution lcd panels are driven by external lcd source drivers, which require a varying number of references. due to nonideal characteristics of the lcd panels, the lcd source drivers must produce nonlinear voltages to the lcd panel. this is called gamma-correction. buffers 1 through 10 have output voltage drive characteristics matched to the gamma correction voltage/current requirements of these panels and are used to drive the reference inputs of the lcd source drivers. all outputs can swing very close to both rails, but the actual limits are determined by the individual channel?s input offset voltage, common-mode input range, and load current being delivered. the input/output characteristics have been set at commonly requested levels. the v com channel has increased output drive capability to meet the drive requirements of the common-node of these panels. the buf11702 is available in the 28-pin powerpad ? package that enables it to meet the power handling requirements of driving these load currents at the required voltage levels. a flow through pin out has been adopted to allow simple pcb routing and maintain the cost effectiveness of this solution. each buffer is capable of driving heavy capacitive loads and offers fast load current switching, often necessary when used to drive large lcds. all inputs and outputs of the buf11702 incorporate internal esd protection circuits that prevent functional failures at voltages up to 2000 v as tested under mil-std-883c method 3015; however care should be exercised in handling these devices as exposure to esd may result in degradation of parametric performance. copyright ? 2001, texas instruments incorporated powerpad is a trademark of texas instruments. production data information is current as of publication date. products conform to specifications per the terms of texas instruments standard warranty. production processing does not necessarily include testing of all parameters. please be aware that an important notice concerning availability, standard warranty, and use in critical applications of texas instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 v dd nc out1 out2 out3 out4 out5 out6 out7 out8 out9 out10 outcom gnd v dd nc in1 in2 in3 in4 in5 in6 in7 in8 in9 in10 incom gnd pwp package (top view) nc ? no internal connection
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 2 post office box 655303 ? dallas, texas 75265 equivalent schematics of inputs and outputs next stage buffer output v s buffer input gnd internal to buf11702 buffer output buffer input v s next stage gnd internal to buf11702 input stage of buffers 1 to 5 and 11 input stage of buffers 6 to 10 previous stage v s buffer output previous stage inverting input internal to buf11702 gnd output stage of all buffers absolute maximum ratings over operating free-air temperature (unless otherwise noted) ? supply voltage, v dd (see note 1) 16.5 v . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . input voltage range, v i v dd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . continuous total power dissipation see dissipation rating table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . operating free-air temperature range, t a 0 c to 85 c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . maximum junction temperature, t j 150 c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . storage temperature range, t stg ? 65 c to 150 c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260 c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ? stresses beyond those listed under ? absolute 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 under ? recommended operating conditions ? is not implied. exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. note 1: all voltage values are with respect to gnd. dissipation rating table package jc ( c/w) ja ( c/w) t a 25 c power rating pwp (28) 0.72 27.9 4.3 w ? see the texas instruments document, powerpad thermally enhanced package application report (literature number slma002), for more information on the powerpad package. the thermal data was measured on a pcb layout based on the information in the section entitled texas instruments recommended board for powerpad on page 33 of the before mentioned document.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 3 post office box 655303 ? dallas, texas 75265 recommended operating conditions min max unit supply voltage, v dd 4.5 16 v buffers 1, 2, 3, 4 & 5 1 v dd common-mode input voltage range, v icr buffers 6, 7, 8, 9 & 10 0 v dd ? 1 v icr v com buffer 1 v dd operating free-air temperature, t a 0 85 c the common-mode input range was chosen to match the expected input/output range required for lcd reference buffers. these devic es are unity-gain buffers, and as such the effective input range will ultimately be limited by the voltage swing of the outputs and wh at load currents are being driven. electrical characteristics over recommended operating free-air temperature range, v dd = 4.5 v to 16 v, t a = 25 c (unless otherwise noted) parameter test conditions t a ? min typ max unit v io in p ut offset voltage v i =v dd /2 r s =50 ? c 1.5 12 mv v io input offset voltage v i = v dd /2 , r s = 50 ? c 1 p a i ib input bias current v i = v dd /2 full range 200 pa k svr su pp ly voltage rejection ratio ( ? v dd / ? v io ) v dd =45vto16v 25 c 62 80 db k svr supply voltage rejection ratio ( ? v dd / ? v io ) v dd = 4 . 5 v to 16 v full range 60 db i dd su pp ly current v o = v dd /2, v i = v dd /2, 25 c 2.5 3.7 ma i dd supply current odd , idd , v dd = 10 v full range 5.5 ma buffer gain v i = 5 v 25 c 0.9995 v/v ? full range is 0 c to 85 c.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 4 post office box 655303 ? dallas, texas 75265 electrical characteristics over recommended operating free-air temperature range, v dd = 4.5 v to 16 v, t a = 25 c (unless otherwise noted) (continued) output characteristics parameter test conditions t a ? min typ max unit v com buffer v dd = 10 v, 25 c 1 1.2 com sinking dd i o = 1 ma to 30 ma full range 2.5 v com buffer v dd = 10 v, 25 c 1 1.2 load regulation com sourcing dd i o = ? 1 ma to ? 30 ma full range 2.5 mv/ma load regulation buffers 1 ? 10 v dd = 10 v, 25 c 0.85 1 mv/ma sinking dd i o = 1 ma to 10 ma full range 1.5 buffers 1 ? 10 v dd = 10 v, 25 c 0.85 1 sourcing dd i o = ? 1 ma to ? 10 ma full range 1.5 v osh1 hi g h-level saturated output buffer 1 v dd = 16 v, i o = ? 10 ma, 25 c 15.85 15.9 v v osh1 g voltage buffer 1 dd , v i = 16 v o , full range 15.8 v v osl10 low-level saturated output buffer 10 v dd = 16 v, i o = 10 ma, 25 c 0.1 0.15 v v osl10 voltage buffer 10 dd , v i = 0 v o , full range 0.2 v v oh1 buffer 1 v dd = 10 v, i o = ? 10 ma, 25 c 9.75 9.8 v v oh1 buffer 1 dd , v i = 9.8 v o , full range 9.7 v v oh2/3/4/5 buffer 2/3/4/5 v dd = 10 v, i o = ? 10 ma, 25 c 9.45 9.5 v v oh2/3/4/5 buffer 2/3/4/5 dd , v i = 9.5 v o , full range 9.4 v v oh6/7/8/9 high level out p ut voltage buffer 6/7/8/9 v dd = 10 v, i o = ? 10 ma, 25 c 7.95 8 v v oh6/7/8/9 high - level output voltage buffer 6/7/8/9 dd , v i = 8 v o , full range 7.9 v v oh10 buffer 10 v dd = 10 v, i o = ? 10 ma, 25 c 7.95 8 v v oh10 buffer 10 dd , v i = 8 v o , full range 7.9 v v ohcom v com buffer v dd = 10 v, i o = ? 30 ma, 25 c 7.95 8 v v ohcom v com buffer dd , v i = 8 v o , full range 7.9 v v ol1 buffer 1 v dd = 10 v, i o = 10 ma, 25 c 2 2.05 v v ol1 buffer 1 dd , v i = 2 v o , full range 2.1 v v ol2/3/4/5 buffer 2/3/4/5 v dd = 10 v, i o = 10 ma, 25 c 2 2.05 v v ol2/3/4/5 buffer 2/3/4/5 dd , v i = 2 v o , full range 2.1 v v ol6/7/8/9 low level out p ut voltage buffer 6/7/8/9 v dd = 10 v, i o = 10 ma, 25 c 0.5 0.55 v v ol6/7/8/9 low - level output voltage buffer 6/7/8/9 dd , v i = 0.5 v o , full range 0.6 v v ol10 buffer 10 v dd = 10 v, i o = 10 ma, 25 c 0.2 0.25 v v ol10 buffer 10 dd , v i = 0.2 v o , full range 0.3 v v olcom v com buffer v dd = 10 v , i o = 30 ma , 25 c 2 2.05 v v olcom v com buffer v dd 10 v, v i = 2 v i o 30 ma, full range 2.1 v ? full range is 0 c to 85 c.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 5 post office box 655303 ? dallas, texas 75265 electrical characteristics over recommended operating free-air temperature range, v dd = 4.5 v to 16 v, t a = 25 c (unless otherwise noted) (continued) ac characteristics parameter test conditions min typ max unit bw 3db 3 db bandwidth buffers 1 ? 10 c l = 100 p f r l =2k ? ? 3db 3 - db bandwidth v com buffer c l = 100 pf , r l = 2 k ? ? 10 c l = 100 pf, r l = 2 k ?, 1 v/ s sr slew rate v com buffer l , v in = 2 v to 8 v l , s transient load regulation disturbance i o = 0 to 5 ma, c l = 100 pf, v o = 5 v, t t = 0.1 s 900 mv transient load response see figure 2 180 mv t s(i-sink) settling time ? current i o = 0 to ? 5 ma, c l = 100 pf v o = 5 v, r l = 2 k ?, 1 s t s(i-source) settling time ? current i o = 0 to 5 ma, c l = 100 pf v o = 5 v, r l = 2 k ?, 2 s buffers 1 10 v i = 4.5 v to 5.5 v 0.1% 6 t settling time voltage buffers 1 ? 10 v i = 5.5 v to 4.5 v 0.1% 4.6 s t s settling time ? voltage v com buffer v i = 4.5 v to 5.5 v 0.1% 5.8 s v com buffer v i = 5.5 v to 4.5 v 0.1% 5.6 v noise voltage buffers 1 ? 10 v i =5v f=1khz 45 nv/ hz v n noise voltage v com buffer v i = 5 v , f = 1 khz 40 nv/ hz crosstalk v ip ? p = 6 v f = 1 khz 85 db
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 6 post office box 655303 ? dallas, texas 75265 parameter measurement information buffer r null r l c l figure 1. bandwidth and phase shift test circuit buffer 5 v r l c l r s c s lcd driver equivalent load v o v 1 t t v tl 5 v test v 1 v tl t t c s r s c l r l source ch1 ? ch10 0 v 2 v 0.1 s 100 pf 100 ? 100 pf 1 k ? sink ch1 ? ch10 10 v 2 v 0.1 s 100 pf 100 ? 100 pf 1 k ? figure 2. transient load response test circuit buffer 5 v c l r l v o t t v tl 5 v r null v tl 10 v 0 v figure 3. transient load regulation test circuit
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 7 post office box 655303 ? dallas, texas 75265 typical characteristics table of graphs figure dc characteristics v io input offset voltage vs input voltage 4, 5, 6 i ib input bias current vs free-air temperature 7 v oh high-level output voltage vs high-level output current 8, 9, 10, 11, 12 v ol low-level output voltage vs low-level output current 13, 14, 15, 16, 17 i dd su pp ly current vs supply voltage 18 i dd supply current vs free-air temperature 19 ac characteristics vs supply voltage 20 bw ? 3 db bandwidth vs free-air temperature 21 vs load capacitance 22, 23, 24 input-output phase shift vs load capacitance 25, 26, 27 psrr power supply rejection ratio vs frequency 28 crosstalk vs frequency 29 v n noise voltage vs frequency 30 z o output impedance vs frequency 31 transient characteristics i dd , v o supply current, output voltage, supply voltage 32 large signal voltage follower 33, 34, 35 small signal voltage follower 36, 38 small signal pulse response 37 transient load res p onse sourcing 39 transient load response sinking 40 sinking 41 transient load regulation sourcing 42 v com 43
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 8 post office box 655303 ? dallas, texas 75265 typical characteristics dc curves figure 4 ? 20 ? 15 ? 10 ? 5 0 5 10 15 20 012345678910 v dd = 10 v channels 1 to 5 input offset voltage vs input voltage v i ? input voltage ? v ? input offset voltage ? mv v io figure 5 ? 20 ? 15 ? 10 ? 5 0 5 10 15 20 02468 10 v dd = 10 v channels 6 to 10 input offset voltage vs input voltage v i ? input voltage ? v ? input offset voltage ? mv v io figure 6 ? 20 ? 15 ? 10 ? 5 0 5 10 15 20 0246810 v dd = 10 v v com buffer input offset voltage vs input voltage v i ? input voltage ? v ? input offset voltage ? mv v io figure 7 0 50 100 150 200 250 0 1020 3040 5060708085 ? input bias current ? pa input bias current vs free-air temperature i ib t a ? free-air temperature ? c v dd = 10 v figure 8 5 6 7 8 9 10 0 50 100 150 200 250 t a = 0 c t a = 25 c t a = 85 c ? high-level output voltage ? v high-level output voltage vs high-level output current v oh i oh ? high-level output current ? ma v dd = 10 v channel 1 figure 9 9 9.2 9.4 9.6 9.8 10 0 10 203040 50 t a = 25 c t a = 85 c ? high-level output voltage ? v high-level output voltage vs high-level output current v oh i oh ? high-level output current ? ma 9.3 9.5 9.7 9.9 9.1 5 152535 45 t a = 0 c v dd = 10 v channel 1 figure 10 5 6 7 8 9 10 0 50 100 150 v dd = 10 v channels 2 to 5 ? high-level output voltage ? v high-level output voltage vs high-level output current v oh i oh ? high-level output current ? ma t a = 85 c t a = 25 c 25 75 125 5.5 6.5 7.5 8.5 9.5 t a = 0 c figure 11 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 t a = 25 c t a = 85 c v dd = 10 v channels 6 to 10 ? high-level output voltage ? v high-level output voltage vs high-level output current v oh i oh ? high-level output current ? ma t a = 0 c 25 75 125 figure 12 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 200 250 t a = 85 c v dd = 10 v v com buffer ? high-level output voltage ? v high-level output voltage vs high-level output current v oh i oh ? high-level output current ? ma t a = 0 c t a = 25 c
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 9 post office box 655303 ? dallas, texas 75265 typical characteristics dc curves (continued) figure 13 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 t a = 25 c t a = 85 c v dd = 10 v channels 1 to 5 ? low-level output voltage ? v low-level output voltage vs low-level output current v ol i ol ? low-level output current ? ma t a = 0 c 25 75 125 figure 14 0 1 2 3 4 5 0 50 100 150 t a = 25 c t a = 85 c v dd = 10 v channels 6 to 9 ? low-level output voltage ? v low-level output voltage vs low-level output current v ol i ol ? low-level output current ? ma t a = 0 c 25 75 125 0.5 1.5 2.5 3.5 4.5 figure 15 0 50 100 150 200 250 t a = 25 c t a = 85 c v dd = 10 v channel 10 ? low-level output voltage ? v low-level output voltage vs low-level output current v ol i ol ? low-level output current ? ma t a = 0 c 0 1 2 3 4 5 0.5 1.5 2.5 3.5 4.5 figure 16 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 010 30 50 t a = 25 c t a = 85 c v dd = 10 v channels 10 ? low-level output voltage ? v low-level output voltage vs low-level output current v ol i ol ? low-level output current ? ma t a = 0 c 520 40 15 25 35 45 figure 17 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 200 250 t a = 25 c t a = 85 c v dd = 10 v v com buffer ? low-level output voltage ? v low-level output voltage vs low-level output current v ol i ol ? low-level output current ? ma t a = 0 c figure 18 0 0.5 1 1.5 2 2.5 3 3.5 4 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 t a = 25 c t a = 70 c t a = 85 c t a = 0 c ? supply current ? ma supply current vs supply voltage v dd ? supply voltage ? v i dd figure 19 0 0.5 1 1.5 2 2.5 3 3.5 4 0 1020304050607080 15 v 10 v 5 v supply current vs free-air temperature ? supply current ? ma i dd t a ? free-air temperature ? c
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 10 post office box 655303 ? dallas, texas 75265 typical characteristics ac curves figure 20 0 0.25 0.5 0.75 1 1.25 0246810121416 channel 9 v com buffer r l = 2 k ? c l = 100 pf t a = 25 c bw ? ? 3 db bandwidth ? mhz ? 3 db bandwidth vs supply voltage v dd ? supply voltage ? v figure 21 0 0.2 0.4 0.6 0.8 1 1.2 0 1020304050607080 bw ? ? 3 db bandwidth ? mhz ? 3 db bandwidth vs free-air temperature t a ? free-air temperature ? c r l = 2 k ? c l = 100 pf 5 v 10, 15 v v com buffer channels 1 to 10 5, 10, 15 v figure 22 0 0.5 1 1.5 2 2.5 3 3.5 0 200 400 600 800 1000 10 v 15 v r l = 2 k ? channel 1 bw ? ? 3 db bandwidth ? mhz ? 3 db bandwidth vs load capacitance c l ? load capacitance ? pf figure 23 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 0 200 400 600 800 1000 10 v 15 v r l = 2 k ? v com buffer bw ? ? 3 db bandwidth ? mhz ? 3 db bandwidth vs load capacitance c l ? load capacitance ? pf figure 24 0 0.5 1 1.5 2 2.5 3 3.5 0 200 400 600 800 1000 r null = 0 r null = 50 v dd = 10 v r l = 2 k ? channel 1 bw ? ? 3 db bandwidth ? mhz ? 3 db bandwidth vs load capacitance c l ? load capacitance ? pf figure 25 0 20 40 60 80 100 120 140 0 100 200 300 400 500 600 700 800 900 1000 5 v 10 v 15 v input-output phase shift input-output phase shift vs load capacitance c l ? load capacitance ? pf r l = 2 k ? channel 1 f = ? 3 db bw figure 26 0 20 40 60 80 100 120 140 0 100 200 300 400 500 600 700 800 900 1000 r null = 0 r null = 50 v dd = 10 v r l = 2 k ? channel 1 f = ? 3 db bw input-output phase shift input-output phase shift vs load capacitance c l ? load capacitance ? pf figure 27 0 5 10 15 20 25 30 35 40 45 50 55 60 0 100 200 300 400 500 600 700 800 900 1000 r l = 2 k ? v com buffer f = ? 3 db bw input-output phase shift input-output phase shift vs load capacitance c l ? load capacitance ? pf v dd = 5 v v dd = 10 v v dd = 15 v figure 28 0 10 20 30 40 50 60 70 80 10 100 1 k 10 k 100 k 1 m 10 m ? power supply rejection ratio ? db f ? frequency ? hz power supply rejection ratio vs frequency psrr channels 1 to 10 v com buffer v dd = 10 v r l = 2 k ? c l = 100 pf
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 11 post office box 655303 ? dallas, texas 75265 typical characteristics ac curves (continued) figure 29 ? 120 ? 110 ? 100 ? 90 ? 80 ? 70 ? 60 ? 50 ? 40 ? 30 ? 20 ? 10 0 10 100 1 k 10 k 100 k 5 v 10 v 15 v r l = 1 k ? c l = 100 pf v i = 60% v dd adjacent channels crosstalk ? db f ? frequency ? hz crosstalk vs frequency figure 30 0 20 40 60 80 100 120 10 100 1 k 10 k 100 k ? noise voltage ? f ? frequency ? hz noise voltage vs frequency nv/ hz v n channels 1 to 10 v com buffer figure 31 0.01 0.1 1 10 100 1000 0.1 k 1 k 10 k 100 k 1 m 10 m v com buffer channel 1 to 10 f ? frequency ? hz ? output impedance ? z o ? output impedance vs frequency
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 12 post office box 655303 ? dallas, texas 75265 typical characteristics transient curves ? 1 0 1 2 3 0 5 10 15 20 25 30 35 40 45 50 0 4 8 12 16 20 t ? time ? ns ? supply current ? ma supply voltage, output voltage and supply current i dd ? output voltage ? v v o ? supply voltage ? v v dd v dd v o ? all channels i dd v dd = 0 to 15 v r l = 2 k ? c l = 100 pf v i = v dd /2 t a = 25 c 0 1 2 3 4 5 024681012141618 0 1 2 3 4 5 channels 1 to 10 v com buffer v i v dd = 5 v v i = 3 v r l = 2 k ? c l = 100 pf t a = 25 c ? output voltage ? v v o t ? time ? ns large signal voltage follower ? input voltage ? v v i figure 32 figure 33 0 2 4 6 8 10 0 5 10 15 20 25 30 0 2 4 6 8 10 t ? time ? ns large signal voltage follower v com buffer v i v dd = 10 v v i = 6 v r l = 2 k ? c l = 100 pf t a = 25 c ? output voltage ? v v o ? input voltage ? v v i channels 1 to 10 0 3 6 9 12 15 0 4 8 12162024283236 0 3 6 9 12 15 large signal voltage follower v dd = 15 v v i = 9 v r l = 2 k ? c l = 100 pf t a = 25 c t ? time ? ns v com buffer v i ? output voltage ? v v o ? input voltage ? v v i channels 1 to 10 figure 34 figure 35
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 13 post office box 655303 ? dallas, texas 75265 typical characteristics transient curves (continued) 2.40 2.45 2.50 2.55 2.60 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 2.40 2.45 2.50 2.55 2.60 t ? time ? ns small signal voltage follower channels 1 to 10 v com buffer v i v dd = 5 v v i = 100 mv r l = 2 k ? c l = 100 pf t a = 25 c ? output voltage ? v v o ? input voltage ? v v i figure 36 4.95 5 5.05 5.10 0 0.50 1 1.50 2 2.50 3 3.50 4 4.50 4.90 4.95 5 5.05 channels 1 to 10 v com buffer v i v dd = 10 v v i = 100 mv r l = 2 k ? c l = 100 pf t a = 25 c ? output voltage ? v v o ? input voltage ? v v i t ? time ? ns small signal pulse response figure 37 7.40 7.45 7.50 7.55 7.60 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 7.40 7.45 7.50 7.55 7.60 t ? time ? ns small signal voltage follower v com buffer v i v dd = 15 v v i = 100 mv r l = 2 k ? c l = 100 pf t a = 25 c ? output voltage ? v v o ? input voltage ? v v i channels 1 to 10 figure 38 figure 39 0 1 2 3 4 5 6 7 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 4.8 4.85 4.9 4.95 5 5.05 5.1 5.15 channel 1 v dd = 10 v, v i = 5 v, c s = 100 pf, r s = 100 ? , c l = 100 pf, r l = 1 k ? , t t = 0.1 s, t a = 25 c transient load pulse t ? time ? ns transient load response ? sourcing ? output voltage ? v v o ? input voltage ? v v lt output voltage
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 14 post office box 655303 ? dallas, texas 75265 typical characteristics transient curves (continued) figure 40 0 1 2 3 4 5 6 7 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 4.8 4.85 4.9 4.95 5 5.05 5.1 t ? time ? ns channel 1 v dd = 10 v, v i = 5 v, c s = 100 pf, r s = 100 ? , c l = 100 pf, r l = 1 k ? , t t = 0.1 s, t a = 25 c transient load response ? sinking ? output voltage ? v v o ? input voltage ? v v lt figure 41 0 1 2 3 4 5 6 012345678 4.6 4.8 5 5.2 5.4 5.6 5.8 c l = 100 pf c l = 1000 pf c l = 10 nf r null = 100 ? t ? time ? ns transient load regulation ? sinking channel 1 v dd = 10 v, v i = 5 v, r l = 1 k ? , t t = 0.1 s, t a = 25 c ? output voltage ? v v o ? load current ? ma i l ? 12 ? 6 0 6 12 0123456789101112131415 3.5 4 4.5 5 5.5 6 t ? time ? ns transient load regulation ? v com buffer c l = 500 pf and 1000 pf c l = 10 nf c l = 100 nf r null = 20 ? v com buffer v dd = 10 v, v i = 5 v, r l = 500 ? , t t = 0.1 s, t a = 25 c ? output voltage ? v v o ? load current ? ma i l sinking sourcing figure 42 0 1 2 3 4 5 6 012345678 4.4 4.6 4.8 5 5.2 5.4 transient load regulation ? sourcing ? output voltage ? v v o ? load current ? ma i l t ? time ? ns channel 1 v dd = 10 v, v i = 5 v, r l = 1 k ? , t t = 0.1 s, t a = 25 c c l = 100 pf c l = 1000 pf c l = 10 nf r null = 100 ? figure 43
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 15 post office box 655303 ? dallas, texas 75265 application information the buf11702 was designed to buffer the gamma correction reference voltages supplied to the digital-to-analog converters (dacs) within the lcd source drivers and provide the voltage/current requirements for lcd panel common node (v com ). see figure 44. buf11702 v com buffer gamma correction buffer 1 ? 10 reference panel timing controller timing and control tms57605 tms57605 start pulse tms57569 out001 out256 out001 out256 1024 768 or 1280 1024 tft-lcd panel tms57569 out001 out384 out001 out384 10 10 v com figure 44. lcd panel drive block diagram depending on the size of the display, the buf11702 will have to drive the gamma correction voltage inputs of a different number of lcd source drivers. a typical lcd source driver available from ti is the tms57569. a 64 gray scale lcd source driver employs internal dacs to convert a 6-bit digital word into a corresponding analog voltage. a 64 gray scale lcd source driver typically has 10 reference nodes to allow for external gamma voltage correction. gamma voltage correction is used to match the characteristic of the lcd source driver chip as close as possible to the characteristic of the actual lcd panel to improve the overall picture quality. external gamma correction voltages are often generated using a simple resistor ladder, as shown in figure 45. the buf11702 acts as a buffer for the various nodes on the gamma correction resistor ladder. due to the low output impedance of the buf11702 it forces the external gamma correction voltage on the respective reference node of the lcd source driver providing an accurate match between the source driver and the lcd panel.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 16 post office box 655303 ? dallas, texas 75265 application information buf11702 gma gma gma gma gma gma gma gma gma gma10 positive polarity negative polarity lcd source driver av dd figure 45. reference buffer for lcd source driver
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 17 post office box 655303 ? dallas, texas 75265 application information gamma correction figure 46 shows a typical 10-reference voltage gamma correction curve. as can be seen from this curve, the various voltages that each buffer encounters vary greatly. v dd1 gma1 gma2 gma3 gma4 gma5 gma6 gma7 gma8 gma9 gma10 v ss1 0 10203040 input data hex0 figure 46. gamma correction curve the lcd source driver dac uses the reference voltages and internal resistor ladder to produce individual voltages for each input code. for gamma correction voltages gma1 through gma5, the voltage levels would be between v dd1 /2 and v dd1 , and for gma6 through gma10, the voltage levels would be between gnd and v dd1 /2. that means that buffers 1 to 5 must have input stages that swing close to the positive rail, but will not have to swing very close to ground (or the negative rail). therefore buffers 1 through 5 have only a single nmos input pair. buffers 6 to 10 have similar but opposite requirements in that they must have input ranges that go down to ground (or negative rail), enabling them to have only a pmos input pair. the output stages have been designed to match the characteristic of the input stage. that means that the output stage of buffer 1 swings very close to the positive range, whereas its ability to swing to gnd (or negative rail) is limited. buffers 2 to 5 have output stages with slightly larger output resistances, as they will not have to swing as close to the positive rail as buffer 1. the converse is true for buffers 6 to 10 in the sense that they have to swing closer to ground than the positive rail. this approach significantly reduces the silicon area and cost of the whole solution. however due to this architecture the right buffer needs to be connected to the right gamma correction voltage. connect buffer 1 to the gamma voltage closest to the positive rail, buffers 2 to 5 to the following voltages. buffer 10 should be connected to the gamma correction voltage closest to gnd (or the negative rail), buffers 9 through 6 to the following voltages. when the lcd source driver has its gamma correction curves matched to the lcd panel, not all 10 reference inputs will be required; quite often only 4 might be used. the quad channel buf4701 is an ideal device for these applications; it combines high drive with wide bandwidth in a 10-pin msop.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 18 post office box 655303 ? dallas, texas 75265 application information driving lcd source drivers with >64 grey scale when a greater number of gray scales are required, two or more buf11702 devices can be used in parallel, see figure 47. this might introduce some redundancy, but still provides a cost-effective way of producing more reference voltages over the use of quad op-amps. buf11702 gma1 gma2 gma3 gma4 gma5 gma6 gma7 gma8 positive polarity negative polarity lcd driver gma9 gma10 gma11 gma12 gma13 gma14 gma15 gma16 out1 out2 out3 out4 out7 out8 out9 out10 out1 out2 out3 out4 out7 out8 out9 out10 buf11702 figure 47. two buf11702 driving a 16-reference lcd source driver an 8-bit source driver typically has 16 to 18 input pins for external gamma correction voltages. using two buf11702 ics, a total of 20 gamma correction voltages can be provided to the respective lcd source driver. despite the possible redundancy, the overall cost of two buf11702s is very competitive.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 19 post office box 655303 ? dallas, texas 75265 application information transient load regulation the buf11702 has been designed to be able to sink/source dc currents in excess of 10 ma. its output stage has been designed to deliver output current transients with little disturbance of the output voltage. however there are times when very fast current pulses are required. therefore, in lcd source driver buffer applications, it is quite normal for capacitors to be placed at the outputs of the reference buffers. these are to improve the transient load regulation. these will typically vary from 100 pf and more. the buf11702 buffers were designed to drive capacitances in excess of 100 pf and retain effective phase margins above 50 , see figure 48. c l ? load capacitance ? pf v dd = 10 v r l = 2 k ? 0 20 40 60 80 100 120 140 10 100 1000 phase shift ? deg figure 48. phase shift between output and input vs load capacitance for buffers 1 ? 10
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 20 post office box 655303 ? dallas, texas 75265 application information transient load regulation (continued) as with all closed-loop amplifiers, if the capacitive load becomes too large, then the phase margin will be reduced, introducing excessive ringing and overshoot. one way of overcoming this is to place series nulling resistors between the output and these load capacitors, see figure 49. buf11702 gma gma gma gma gma gma gma gma gma gma1 positive polarity negative polarity lcd source driver out1 out2 out3 out4 out5 out6 out7 out8 out9 out10 figure 49. buf11702 driving a lcd source driver with series nulling resistors
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 21 post office box 655303 ? dallas, texas 75265 application information common buffer (v com ) the common buffer output of the buf11702 has a greater output drive capability than buffers 1 ? 10, to meet the heavier current demands of driving the common node of the lcd panel. it was also designed to drive heavier capacitive loads and still remain stable, see figure 50. 0 5 10 15 20 25 30 35 40 45 10 100 1000 phase shift ? deg c l ? load capacitance ? pf v dd = 10 v r l = 2 k ? figure 50. phase shift between output and input vs load capacitance for common buffer because the common node of the panel acts like a large capacitor, the common output of the buf11702 will have to supply very large pulses of current. in some applications the output drive capability of the buf11702 might not be sufficient. therefore discrete amplifiers with high output current drive capability and enough phase margin to drive large capacitive loads could be used. possible alternatives include the opa551, opa350, buf634, tlc081 or tlv4110/1. because of their wide bandwidth and the low frequency pole created by the lcd panel common node capacitance, extra compensation may be required.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 22 post office box 655303 ? dallas, texas 75265 application information general powerpad design considerations the buf11702 is available in the thermally enhanced powerpad family of packages. these packages are constructed using a downset leadframe upon which the die is mounted [see figure 51(a) and figure 51(b)]. this arrangement results in the lead frame being exposed as a thermal pad on the underside of the package [see figure 51(c)]. because this thermal pad has direct thermal contact with the die, excellent thermal performance can be achieved by providing a good thermal path away from the thermal pad. the powerpad package allows for both assembly and thermal management in one manufacturing operation. during the surface-mount solder operation (when the leads are being soldered), the thermal pad can also be soldered to a copper area underneath the package. through the use of thermal paths within this copper area, heat can be conducted away from the package into either a ground plane or other heat-dissipating device. die side view (a) end view (b) bottom view (c) die thermal pad note a: the thermal pad is electrically isolated from all terminals in the package. figure 51. views of thermally enhanced dgn package although there are many ways to properly heatsink the powerpad package, the following steps illustrate the recommended approach. y mils x z mils with 18 vias (via diameter = 13 mils) figure 52. powerpad pcb etch and via pattern
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 23 post office box 655303 ? dallas, texas 75265 application information general powerpad design considerations (continued) 1. prepare the pcb with a top side etch pattern as shown in figure 52. there should be etching for the leads as well as etch for the thermal pad. 2. place eighteen holes in the area of the thermal pad. these holes should be 13 mils in diameter. keep them small so that solder wicking through the holes is not a problem during reflow. 3. additional vias may be placed anywhere along the thermal plane outside of the thermal pad area. this helps dissipate the heat generated by the buf11702 ic. these additional vias may be larger than the 13-mil diameter vias directly under the thermal pad. they can be larger because they are not in the thermal pad area to be soldered so that wicking is not a problem. 4. connect all holes to the internal ground plane. 5. when connecting these holes to the ground plane, do not use the typical web or spoke via connection methodology. web connections have a high thermal resistance connection that is useful for slowing the heat transfer during soldering operations. this makes the soldering of vias that have plane connections easier. in this application, however, low thermal resistance is desired for the most efficient heat transfer. therefore, the holes under the buf11702 powerpad package should make their connection to the internal ground plane with a complete connection around the entire circumference of the plated-through hole. 6. the topside solder mask should leave the terminals of the package and the thermal pad area with its five holes (dual) or nine holes (quad) exposed. the bottom-side solder mask should cover the five or nine holes of the thermal pad area. this prevents solder from being pulled away from the thermal pad area during the reflow process. 7. apply solder paste to the exposed thermal pad area and all of the ic terminals. 8. with these preparatory steps in place, the buf11702 ic is simply placed in position and run through the solder reflow operation as any standard surface-mount component. this results in a part that is properly installed.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 24 post office box 655303 ? dallas, texas 75265 application information general powerpad design considerations (continued) for a given ja , the maximum power dissipation is shown in figure 53 and is calculated by the following formula: p d t max ? t a ja where: p d = maximum power dissipation of buf11702 ic (watts) t max = absolute maximum junction temperature (150 c) t a = free-ambient air temperature ( c) ja = jc + ca jc = thermal coefficient from junction to case (0.72 c/w) ca = thermal coefficient from case to ambient air ( c/w) maximum power dissipation vs free-air temperature 7 6 5 4 3 2 ? 40 ? 200 204060 t a ? free-air temperature ? c w 1 maximum power dissipation ? 80 100 8 t j = 150 c 0 ja = 27.9 c/w 2 oz. trace and copper pad with solder figure 53. maximum power dissipation vs free-air temperature this lower thermal resistance enables the buf11702 to deliver maximum output currents even at high ambient temperatures.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 25 post office box 655303 ? dallas, texas 75265 application information buf11702 evaluation module (slop356) the buf11702 has an evaluation module where it can be mounted along with reference resistors and load capacitors. this enables the buf11702 to be used in its own daughterboard in existing designs for easy evaluation. the schematic of the buf11702 evm is shown below. note that the evm has been configured for single supply use. as such, all decoupling capacitors are connected to the ground plane of the evm, as are the ground terminals of the buf11702. buf11702 outcom ch10 ch9 ch8 ch7 ch6 ch5 ch4 ch3 ch2 outcom out10 out9 out8 out7 out6 out5 out4 out3 out2 r 22 r 21 r 20 r 19 r 18 r 17 r 16 r 15 r 14 ch1 out1 r 12 r 13 c 16 c 15 c 14 c 13 c 12 c 11 c 10 c 9 c 8 c 7 c 6 r 23 r 24 r 25 r 26 r 27 r 28 r 29 r 30 r 31 r 32 gnd gnd v dd gnd nc v dd gnd incom in10 in9 in8 in7 in6 in5 in4 in3 in2 in1 nc v dd jp1 c 4 v dd2 v dd gnd c 1 c 2 c 3 jp2 r 11 r 10 r 9 r 8 r 7 r 6 r 5 r 4 r 3 r 2 r 1 jp3 vref incom ch10 ch9 ch8 ch7 ch6 ch5 ch4 ch3 ch2 ch1 j2 j3 j1 figure 54. buf11702 evaluation module schematic in populated versions of the evm, capacitors c 1 to c 4 have been included. capacitors c1 and c2 are bulk decoupling capacitors of 6.8 f while capacitors c 3 and c 4 are 100 nf ceramic high frequency decoupling capacitors. resistors r 1 to r 32 and capacitors c 5 to c 16 have not been included and are application specific.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 26 post office box 655303 ? dallas, texas 75265 application information reference voltages the reference voltages can be supplied externally via the connector j2 (not included) or generated onboard via resistors r 1 to r 11 . provision on the board for an external low side reference has been included so that the nega- tive references can be referred to a voltage other than ground. the reference ladder can be referred to either v dd (master supply voltage) or a secondary voltage, v dd2 . this allows a low noise or absolute reference voltage to be used for the lcd source driver ? s dacs other than the system voltage. if the secondary voltage is used, then jumper jp1 should be left open and jumper jp2 shorted. if a ratiometric reference (proportional to the master supply voltage) is to be used, then jumper jp1 and jp2 should be shorted, feeding v dd through to the reference ladder. output the outputs of the buf11702 are fed to connector j3 (not mounted). this enables the output voltages to be monitored directly on the evm or fed off-board for evaluation in a real system. onboard load resistors, r 23 to r 32 , connected to ground can also be mounted. these can be used to simulate resistive loading of the lcd source driver. transient improving capacitors are frequently used in lcd panel applications, and so pads to mount these tran- sient improving capacitors, c 6 to c 16 , have been included. due to the possible magnitude of these capacitors, pads have been placed between the output of the buf11702 and these capacitors to mount nulling resistors, r12 to r22. if the nulling resistors are not required, shorts could be placed instead of resistors. the pads for r1 to r32 and capacitors c3 to c16 have been laid out to support 0805 or 1206 size components. powerpad the evm has been laid out to support the powerpad feature of the buf11702. an area is provided on the evm, under the buf11702, for the exposed leadframe to be connected to. eighteen vias are connected to the ground plane of the evm to reduce the thermal case to ambient resistance, ca , significantly. see applications section on general powerpad design considerations.
buf11702 10+1-channel lcd gamma correction buffer slos359b ? march 2001 ? revised october 2001 27 post office box 655303 ? dallas, texas 75265 mechanical data pwp (r-pdso-g**) powerpad ? plastic small-outline 4073225/f 10/98 0,50 0,75 0,25 0,15 nom thermal pad (see note d) gage plane 28 24 7,70 7,90 20 6,40 6,60 9,60 9,80 6,60 6,20 11 0,19 4,50 4,30 10 0,15 20 a 1 0,30 1,20 max 16 14 5,10 4,90 pins ** 4,90 5,10 dim a min a max 0,05 seating plane 0,65 0,10 m 0,10 0 ? 8 20 pins shown notes: a. all linear dimensions are in millimeters. b. this drawing is subject to change without notice. c. body dimensions do not include mold flash or protrusions. d. the package thermal performance may be enhanced by bonding the thermal pad to an external thermal plane. this pad is electrically and thermally connected to the backside of the die and possibly selected leads. e. falls within jedec mo-153 powerpad is a trademark of texas instruments.
important notice texas instruments incorporated and its subsidiaries (ti) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. all products are sold subject to ti ? s terms and conditions of sale supplied at the time of order acknowledgment. ti warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with ti ? s standard warranty. testing and other quality control techniques are used to the extent ti deems necessary to support this warranty. except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. ti assumes no liability for applications assistance or customer product design. customers are responsible for their products and applications using ti components. to minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. ti does not warrant or represent that any license, either express or implied, is granted under any ti patent right, copyright, mask work right, or other ti intellectual property right relating to any combination, machine, or process in which ti products or services are used. information published by ti regarding third ? party products or services does not constitute a license from ti to use such products or services or a warranty or endorsement thereof. use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from ti under the patents or other intellectual property of ti. reproduction of information in ti data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. reproduction of this information with alteration is an unfair and deceptive business practice. ti is not responsible or liable for such altered documentation. resale of ti products or services with statements different from or beyond the parameters stated by ti for that product or service voids all express and any implied warranties for the associated ti product or service and is an unfair and deceptive business practice. ti is not responsible or liable for any such statements. mailing address: texas instruments post office box 655303 dallas, texas 75265 copyright ? 2001, texas instruments incorporated

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