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dual 256-position spi digital potentiometer ad5162 rev. a in fo rmation furn ished by an alog d e v i c e s is believed to be accurate and reliable. how e ver, n o resp on sibili ty is assume d b y a n alog de vices fo r its use, nor for an y i n fri n geme nt s of p a t e nt s or ot h e r ri ght s o f th ird parties th at may result fro m its use . specifications subjec t to chan g e witho u t n o tice. no licen s e is g r an te d by implicati o n or ot herwi s e u n der a n y p a t e nt or p a t e nt ri ghts of analog de v i ces. trademarks an d registered tra d ema r ks are the prop erty o f their respective ow ners. one technolog y way, p.o . box 9106, norwood, ma 02062-9106, u.s.a. t e l: 781. 329. 4 700 www.analog.com fax: 781. 326. 87 03 ? 2003 analog de vices, i n c. al l r i ght s r e ser v ed . features 2-channel, 25 6 - position end-to-end r e s istance: 2. 5 k?, 10 k?, 50 k?, 100 k? compact msop-10 ( 3 mm 4. 9 mm) package fast settling ti me: t s = 5 s typical on power - up full re ad/write of wiper register power-on preset to midscale extra package address decod e pin ad 0 computer software replaces c in factory pr ogramming applications single supply: 2.7 v to 5.5 v low temperature coefficient: 35 ppm/c low power: i dd = 6 a max wide operatin g temperature: ?40 c to + 125 c evaluation board available applic ati o ns systems calibr ations electronics level settings mechanical trimmers? replacement in new d e signs permanent fac t ory pcb settin g transducer adj u stment of pre ssure, tempera t ure, position, chemical, and optical sensors rf amplifier bi asing automotive e l ectronics adjustment gain control and offset a d just ment func tio n a l block di agram a 1 a = 0 a = 1 v dd gnd sdi clk cs w1 wiper register 1 spi inter f a c e ad5162 04108-0-001 b1 w2 wiper register 2 b2 fi g u r e 1 . general description the ad5162 p r o v ides a com p ac t 3 mm 4.9 mm p a c k a g e d s o l u tio n f o r d u a l 256-p o si tio n ad j u s t m e n t a p p l ica t ion s . this d e v i ce pe rf o r m s th e sa m e e l ectr o n i c a d j u s t m e n t fun c ti o n a s a 3 - te r m i n a l me c h ani c a l p o te n t i o me te r . a v a i l a bl e i n fou r di f f e r e n t end-t o -en d r e sis t an ce va l u es (2.5 k?, 10 k?, 50 k?, 100 k?), t h is lo w t e m p er a t ur e co ef f i cien t de vice is i d e a l fo r hig h acc u - r a c y and s t abi l it y v a r i abl e re s i st anc e a d j u st m e n t s . t h e w i p e r s e t t i n g s are c o n t rol l abl e t h rou g h an spi d i g i t a l i n te r f a c e. t h e r e sis t a n c e b e twe e n t h e wi p e r and ei t h er e n d p oin t o f t h e f i xe d re s i stor v a r i e s l i ne arly wi t h re sp e c t to t h e dig i t a l c o de tra n sf e r r e d i n t o th e rd a c 1 la t c h. 1 the terms di g i tal pote n t i o me te r , vr , and rdac are use d inte rchange a bl y. o p era t ing f r o m a 2.7 v t o 5.5 v p o w e r s u p p l y a nd co n s u m in g les s tha n 6 a a l lo ws th e ad51 62 t o be us e d in p o r t a b le b a t t er y-o p era t e d a p pli c a t io n s . f o r a p p l ica t ion s tha t p r og ra m t h e ad5162 a t t h e fac t o r y , ana l o g d e vi ces o f fers de vice p r o g r a mmin g s o f t wa r e r u nnin g o n w i n d o w s? nt/2000/xp o p era t in g syst em s. this s o f t wa r e ef fe c t i v e l y r e places a n y ext e r n al s p i co n t r o l l ers, w h ich in t u r n enhan c es us ers sys t em s time-t o - ma rk et. an ad5162 eval u a tion ki t and s o f t wa r e a r e a v a i la b l e . th e k i t i n cl u d es a ca b l e and in st r u c t io n man u a l .
ad5162 rev. a | page 2 of 20 table of contents electrical characteristics2.5 k? version ................................... 3 electrical characteristics10 k?, 50 k?, 100 k? versions ....... 4 timing characteristicsall versions ........................................... 5 absolute maximum ratings ............................................................ 6 esd caution .................................................................................. 6 pin configuration and function descriptions ............................. 7 pin configuration ......................................................................... 7 pin function descriptions .......................................................... 7 typical performance characteristics ............................................. 8 te s t c i rc u it s ..................................................................................... 12 theory of operation ...................................................................... 13 prog ramming t he var iable resi stor and volt age .................... 13 programming the potentiometer divider ............................... 14 esd protection ........................................................................... 14 terminal voltage operating range .......................................... 14 power-up sequence ................................................................... 14 layout and power supply bypassing ....................................... 15 constant bias to retain resistance setting ............................. 15 evaluation board ........................................................................ 15 spi interface .................................................................................... 16 spi compatible 3-wire serial bus ........................................... 16 outline dimensions ....................................................................... 17 ordering guide .......................................................................... 17 revision history 11/03 changed from rev. 0 to rev. a: changes to electrical characteristics.................................... page 3 11/03 revision 0: initial version
ad5162 rev. a | page 3 of 20 electrical characteristics2.5 k? version table 1. v dd = 5 v 10%, or 3 v 10%; v a = +v dd ; v b = 0 v; ? 40c < t a < +125c; unless otherwise noted parameter symbol conditions min typ 1 max unit dc characteristicsrheostat mode resistor differential nonlinearity 2 r-dnl r wb , v a = no connect ?2 0.1 +2 lsb resistor integral nonlinearity 2 r-inl r wb , v a = no connect ?6 0.75 +6 lsb nominal resistor tolerance 3 ? r ab t a = 25c ?20 +55 % resistance temperature coefficient (?r ab /r ab )/?t v ab = v dd , wiper = no connect 35 ppm/c r wb (wiper resistance) r wb code = 0x00, v dd = 5 v 160 200 ? dc characteristicspotentiometer divider mode (specifications apply to all vrs) differential nonlinearity 4 dnl ?1.5 0.1 +1.5 lsb integral nonlinearity inl ?2 0.6 +2 lsb voltage divider temperature coefficient (?v w /v w )/?t code = 0x80 15 ppm/c full-scale error v wfse code = 0xff ?10 ?2.5 0 lsb zero-scale error v wzse code = 0x00 0 2 10 lsb resistor terminals voltage range 5 v a, b, w gnd v dd v capacitance 6 a, b c a, b f = 1 mhz, measured to gnd, code = 0x80 45 pf capacitance 6 w c w f = 1 mhz, measured to gnd, code = 0x80 60 pf common-mode leakage i cm v a = v b = v dd /2 1 na digital inputs and outputs input logic high v ih v dd = 5 v 2.4 v input logic low v il v dd = 5 v 0.8 v input logic high v ih v dd = 3 v 2.1 v input logic low v il v dd = 3 v 0.6 v input current i il v in = 0 v or 5 v 1 a input capacitance 6 c il 5 pf power supplies power supply range v dd range 2.7 5.5 v supply current i dd v ih = 5 v or v il = 0 v 3.5 6 a power dissipation 7 p diss v ih = 5 v or v il = 0 v, v dd = 5 v 30 w power supply sensitivity pss v dd = 5 v 10%, code = midscale 0.02 0.08 %/% dynamic characteristics 8 bandwidth ?3 db bw_2.5 k code = 0x80 4.8 mhz total harmonic distortion thd w v a = 1 v rms, v b = 0 v, f = 1 khz 0.1 % v w settling time t s v a = 5 v, v b = 0 v, 1 lsb error band 1 s resistor noise voltage density e n_wb r wb = 1.25 k?, r s = 0 3.2 nv/ hz see notes at end of section.
ad5162 rev. a | page 4 of 20 electrical characteristics10 k?, 50 k?, 100 k? versions table 2. v dd = 5 v 10%, or 3 v 10%; v a = v dd ; v b = 0 v; ?40c < t a < 125c; unless otherwise noted parameter symbol conditions min typ 1 max unit dc characteristicsrheostat mode resistor differential nonlinearity 2 r-dnl r wb , v a = no connect ?1 0.1 +1 lsb resistor integral nonlinearity 2 r-inl r wb , v a = no connect ?2.5 0.25 +2.5 lsb nominal resistor tolerance 3 ? r ab t a = 25c ?20 +20 % resistance temperature coefficient (?r ab /r ab )/?t v ab = v dd , wiper = no connect 35 ppm/c r wb (wiper resistance) r wb code = 0x00, v dd = 5 v 160 200 ? dc characteristicspotentiometer divider mode (specifications apply to all vrs) differential nonlinearity 4 dnl ?1 0.1 +1 lsb integral nonlinearity 4 inl ?1 0.3 +1 lsb voltage divider temperature coefficient (?v w /v w )/?t code = 0x80 15 ppm/c full-scale error v wfse code = 0xff ?2.5 ?1 0 lsb zero-scale error v wzse code = 0x00 0 1 2.5 lsb resistor terminals voltage range 5 v a,b,w gnd v dd v capacitance 6 a, b c a,b f = 1 mhz, measured to gnd, code = 0x80 45 pf capacitance 6 w c w f = 1 mhz, measured to gnd, code = 0x80 60 pf common-mode leakage i cm v a = v b = v dd /2 1 na digital inputs and outputs input logic high v ih v dd = 5 v 2.4 v input logic low v il v dd = 5 v 0.8 v input logic high v ih v dd = 3 v 2.1 v input logic low v il v dd = 3 v 0.6 v input current i il v in = 0 v or 5 v 1 a input capacitance c il 5 pf power supplies power supply range v dd range 2.7 5.5 v supply current i dd v ih = 5 v or v il = 0 v 3.5 6 a power dissipation p diss v ih = 5 v or v il = 0 v, v dd = 5 v 30 w power supply sensitivity pss v dd = 5 v 10%, code = midscale 0.02 0.08 %/% dynamic characteristics bandwidth ?3 db bw r ab = 10 k?/50 k?/100 k?, code = 0x80 600/100/40 khz total harmonic distortion thd w v a = 1 v rms, v b = 0 v, f = 1 khz, r ab = 10 k? 0.1 % v w settling time (10 k?/50 k?/100 k?) t s v a = 5 v, v b = 0 v, 1 lsb error band 2 s resistor noise voltage density e n_wb r wb = 5 k?, r s = 0 9 nv/ hz see notes at end of section.
ad5162 rev. a | page 5 of 20 timing characteristicsall versions table 3. v dd = +5 v 10%, or +3 v 10%; v a = v dd ; v b = 0 v; ?40c < t a < +125c; unless otherwise noted parameter symbol conditions min typ 1 max unit spi interface timing characteristics 9 (specifications apply to all parts) clock frequency f clk 25 mhz input clock pulse width t ch , t cl clock level high or low 20 ns data setup time t ds 5 ns data hold time t dh 5 ns cs setup time t css 15 ns cs high pulse width t csw 40 ns clk fall to cs fall hold time t csh0 0 ns clk fall to cs rise hold time t csh1 0 ns cs rise to clock rise setup t cs1 10 ns see notes at end of section. notes 1 typical specifications represe nt average readings at 25c and v dd = 5 v. 2 resistor position nonlinearity error r-inl is the deviation from an ideal value measured betw een the maximum re sistance and th e minimum resistance wiper positions. r-dnl measures the relative step change from ideal between successive tap positions. parts are guaranteed monotonic. 3 v ab = v dd , wiper (vw) = no connect. 4 inl and dnl are measured at v w with the rdac configured as a potentiometer divide r similar to a voltage output dac converter. v a = v dd and v b = 0 v. dnl specification limits of 1 lsb maximum are guaranteed monotonic operating conditions. 5 resistor terminals a, b, w ha ve no limitations on polarity with respect to each other. 6 guaranteed by design and not subject to production test. 7 p diss is calculated from (i dd v dd ). cmos logic level inputs result in minimum power dissipation. 8 all dynamic characteristics use v dd = 5 v. 9 see timing diagrams for locati ons of measured values.
ad5162 r e v. a | pa ge 6 o f 2 0 absolute maximum ratings table 4. t a = 2 5 c, u n les s ot herwi s e not e d parameter value v dd to gnd C0.3 v to +7 v v a , v b , v w to gn d v dd terminal curren t , ax to bx, ax to wx, bx to wx 1 pulsed 20 ma continuous 5 ma digital inputs and output volt age to gnd 0 v to 7 v operating tem p erature range C40c to +125c maximum junction temperature (t jmax ) 150c storage temperature C65c to +150c lead temperature (soldering, 10 s) 300c t h ermal resista n ce 2 ja : msop-1 0 230c/w 1 maximum terminal current is bounde d by the maximum c urrent handling of the s w itches , maxi m um power d i ss ip ation of the package, and maximum appl ied vol t age acros s any two of the a , b, and w terminal s at a given resi st a n ce. 2 pa cka g e pow e r di s s i p a t i o n = (t jm ax ? t a )/ ja . s t r e s s es a b o v e t h os e lis t e d u n de r a b s o l u t e m a xi m u m r a t i n g s ma y c a us e p e r m a n en t dama ge t o t h e de vice . this is a s t r e s s ra t i n g onl y ; f u n c t i o n al o p era t ion o f t h e de vice a t t h es e o r an y o t h e r con d i t io ns a b o v e t h o s e i ndic a te d i n t h e op er a t io na l s e c t io n o f t h is sp e c if ic a t io n is no t im plie d . e x p o sur e t o a b s o l u te max i m u m ra t i ng co ndi t i on s fo r ex ten d e d p e r i o d s ma y a f fe c t de vice r e l i ab i l i t y . esd caution esd (electrostatic discharge) sensitive device. ele c tros tatic charg e s as high as 4000 v readily accumulate on the human body and test eq uipment and can discharge wi thout detection. although this product features proprietary esd protection circu i try, permanent dama ge may occur on devices subjected to high energy electrostatic discharges. theref ore, prop er esd precautions a r e recommended to avoid perform a nce degradation or l o ss of functiona l ity.
ad5162 r e v. a | pa ge 7 o f 2 0 pin conf iguration and fu nction descriptions pin c o nfig uratio n 10 9 8 7 1 2 3 4 b1 a1 w2 w1 b2 cs sdi gnd 6 5 clk v dd top view ad5162 04108-0-002 fi g u r e 2 . pin func ti on descrip t io ns table 5. pin no. m n e m o n i c d e s c r i p t i o n 1 b1 b1 terminal. 2 a1 a1 terminal. 3 w2 w2 terminal. 4 gnd digital ground. 5 v dd positive power s u pply. 6 clk serial clock input. positive edg e triggered. 7 sdi serial data inpu t. 8 cs chip select inpu t, active low. when cs returns high, data is loaded into the dac register. 9 b2 b2 terminal. 10 w1 w1 terminal.
ad5162 r e v. a | pa ge 8 o f 2 0 typical perf orm ance cha r acte ristics ?2.0 ?1.5 ?1.0 ?0.5 0 0.5 rheostat mode inl (lsb) 1.0 1.5 2.0 12 8 96 32 64 0 1 60 192 224 256 code (decimal) 04108-0-003 v dd = 5.5v t a = 25c r ab = 10k ? v dd = 2.7v f i gur e 3 . r - inl vs . co de vs . sup p l y v o l t a g e s ?0.5 ?0.4 ?0.3 ?0.2 ?0.1 0 0.1 0.2 0.3 0.4 0.5 rhe os tat mode dnl (ls b ) 12 8 96 32 64 0 1 60 192 224 256 code (decimal) 04108-0-004 t a = 25c r ab = 10k ? v dd = 2.7v v dd = 5.5v f i gur e 4 . r - dnl vs . c o de vs . sup p l y v o lta g e s ?0.5 ?0.4 ?0.3 ?0.2 ?0.1 0 0.1 0.2 0.3 0.4 0.5 p o te ntiome te r mode inl (ls b ) 12 8 96 32 64 0 1 60 192 224 256 code (decimal) 04108-0-005 r ab = 10k ? v dd = 2.7v t a = ? 40c, +25c, +85c, +125c v dd = 5.5v t a = ? 40c, +25c, +85 c, +125c f i gur e 5 . inl vs . code vs . t e m p e r a t ur e ?0.5 ?0.4 ?0.3 ?0.2 ?0.1 0 0.1 0.2 0.3 0.4 0.5 p o te ntiome te r mode dnl (ls b ) 12 8 96 32 64 0 1 60 192 224 256 code (decimal) 04108-0-006 v dd = 2.7v; t a = ? 40 c, +25c, +85c, +125c r ab = 10k ? f i gur e 6 . dnl vs . c o de vs . t e m p e r a t ur e ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 1.0 p o te ntiome te r mode inl (ls b ) 12 8 96 32 64 0 1 60 192 224 256 code (decimal) 04108-0-007 t a = 25c r ab = 10k ? v dd = 2.7v v dd = 5.5v f i gur e 7 . inl vs . code vs . sup p l y v o l t age s ?0.5 ?0.4 ?0.3 ?0.2 ?0.1 0 0.1 0.2 0.3 0.4 0.5 p o te ntiome te r mode dnl (ls b ) 12 8 96 32 64 0 1 60 192 224 256 code (decimal) 04108-0-008 t a = 25c r ab = 10k ? v dd = 2.7v v dd = 5.5v f i gur e 8 . dnl vs . c o de vs . sup p l y v o l t a g e s
ad5162 r e v. a | pa ge 9 o f 2 0 ?2.0 ?1.5 ?1.0 ?0.5 0 0.5 rheostat mode inl (lsb) 1.0 1.5 2.0 12 8 96 32 64 0 1 60 192 224 256 code (decimal) 04108-0-009 r ab = 10k ? v dd = 2.7v t a = ? 40 c, +25c, +85c, +125c v dd = 5.5v t a = ? 40c, +25c, +85 c, +125c f i gur e 9 . r - inl vs . co de vs . t e m p e r a t ur e ?0.5 ?0.4 ?0.3 ?0.2 ?0.1 0 0.1 0.2 0.3 0.4 0.5 rhe os tat mode dnl (ls b ) 12 8 96 32 64 0 1 60 192 224 256 code (decimal) 04108-0-010 v dd = 2.7v, 5.5v; t a = ? 40c, +25 c, +85c, +125c r ab = 10k ? f i gur e 1 0 . r - dnl vs . c o de vs . t e m p e r a t ur e ?2.0 ?1.5 ?1.0 ?0.5 0 0.5 fse, fu ll- sc a l e er r o r ( l sb ) 1.0 1.5 2.0 temperature ( c) ?40 ? 25 ? 1 0 5 20 35 50 65 80 95 110 125 04108-0-011 v dd = 5.5v, v a = 5.0v r ab = 10k ? v dd = 2.7v, v a = 2.7v f i gure 11. f u ll- s c al e e rror v s . t e m p er a t ur e 0 0.75 1.50 2.25 3.00 3.75 4.50 zs e , ze ro-s cale e rror (ls b ) temperature ( c) ?40 ? 25 ? 1 0 5 20 35 50 65 80 95 110 125 04108-0-012 v dd = 5.5v, v a = 5.0v r ab = 10k ? v dd = 2.7v, v a = 2.7v f i gure 12. zero -s c a le e r r o r v s . t e mpe r a t ur e i dd , s u p p l y curre nt ( a) 0.1 1 10 ? 4 0 ? 7 2 6 5 9 9 2 125 temperature ( c) 04108-0-013 v dd = 5v v dd = 3v f i gure 13. sup p l y current v s . t e mper at ur e ?2 0 0 20 40 60 80 100 120 rheostat mode te mp co (ppm/ c) 12 8 96 32 64 0 1 60 192 224 256 code (decimal) 04108-0-014 r ab = 10k ? v dd = 2.7v t a = ? 40c to +85 c, ? 40c to +125c v dd = 5.5v t a = ? 40c to +85c, ? 40c to +125 c f i g u re 14. r h e o s t at m o de t e mpco ?r wb /?t v s . code
ad5162 rev. a | page 10 of 20 ?30 ?20 ?10 0 10 20 p o te ntiome te r mode te mp co (ppm/ c) 30 40 50 12 8 96 32 64 0 1 60 192 224 256 code (decimal) 04108-0-015 r ab = 10k ? v dd = 2.7v t a = ? 40c to +85c, ? 40c to +125c v dd = 5.5v t a = ? 40c to +85c, ? 40 c to +125 c f i gure 1 5 . p o tentiom e ter m o de t e m p co ?v wb /? t v s . code ?60 ?54 ?48 ?42 ?36 ?30 ?24 ?18 ?12 ?6 0 gain ( d b) frequency (hz) 10k 1m 100k 10m 04108-0-016 0x80 0x40 0x20 0x10 0x08 0x04 0x01 0x02 f i gure 16. g a in vs. f r equ e nc y vs. c o d e , r ab = 2. 5 k ? ?60 ?54 ?48 ?42 ?36 ?30 ?24 ?18 ?12 ?6 0 gain ( d b) frequency (hz) 1k 100k 10k 1m 04108-0-017 0x80 0x40 0x20 0x10 0x08 0x04 0x01 0x02 f i gure 17. g a in vs. f r equ e nc y vs. c o d e , r ab = 10 k? ?60 ?54 ?48 ?42 ?36 ?30 ?24 ?18 ?12 ?6 0 gain ( d b) frequency (hz) 1k 100k 10k 1m 04108-0-018 0x80 0x40 0x20 0x10 0x08 0x04 0x01 0x02 f i gure 18. g a in vs. f r equ e nc y vs. c o d e , r ab = 50 k? ?60 ?54 ?48 ?42 ?36 ?30 ?24 ?18 ?12 ?6 0 gain ( d b) frequency (hz) 1k 100k 10k 1m 04108-0-019 0x80 0x40 0x20 0x10 0x08 0x04 0x01 0x02 f i gure 19. g a in vs. f r equ e nc y vs. c o d e , r ab = 10 0 k? ?60 ?54 ?48 ?42 ?36 ?30 ?24 ?18 ?12 ?6 0 gain ( d b) frequency (hz) 10k 1k 100k 1m 10m 04108-0-020 100k ? 60khz 50k ? 120khz 10k ? 570khz 2.5k ? 2.2mhz f i gure 20. C3 db bandwidth @ code = 0x80
ad5162 rev. a | page 11 of 20 i dd , s u p p l y curre nt (ma) 0.01 1 0.1 10 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 digital input voltage (v) 04108-0-025 t a = 25c v dd = 2.7v v dd = 5.5v f i g u re 21. i dd vs . input v o l t a g e 04108-0-021 v w clk f i gure 2 2 . di g i ta l f eedthro u g h 04108-0-022 v w2 v w1 f i g u re 23. d i g i t a l c r os s t a l k 04108-0-024 v w2 v w1 f i g u re 24. a n a l og cr os s t alk 04108-0-026 v w f i g u re 25. m i ds c a l e gli t ch, cod e 0x 80 t o 0x 7f 04108-0-023 v w cs f i gure 2 6 . la r g e s i gna l s e ttli n g t i m e
ad5162 rev. a | page 12 of 20 test circuits f i g u re 2 7 t h rou g h f i g u re 3 2 i l lu st r a te t h e te st c i rc u i t s t h at def i ne t h e t e st c o n d i t io ns us e d i n t h e p r o d uc t sp e c if ic a t io n ta b l e s . 04108-0-027 v ms a w b dut v+ v+ = v dd 1lsb = v+/2 n f i gure 27. t e s t c i rc uit for p o tenti o meter d i v i de r n o nl in ea rit y e r r o r (inl, dnl) 04108-0-028 no connect i w v ms a w b dut f i gure 28. t e s t c i rc uit for r e s i s t or p o s i tion non l i n e a r i t y e rror (r heo s ta t o p er a t ion; r - inl, r - dnl) 04108-0-029 v ms2 v ms1 v w a w b dut i w = v dd /r nominal r w = [v ms1 ? v ms2 ]/i w f i gur e 2 9 . t e st c i r c ui t fo r wi p e r resi st a n c e 04108-0-030 ? v ms % dut ( ) a w b v+ ? v dd % ? v ms ? v dd ? v dd v a v ms v+ = v dd 10% psrr (db) = 20 log pss (%/%) = f i g u re 30. t e s t c i rc uit f o r p o wer sup p l y s e ns it iv it y (pss, pssr) 04108-0-031 +15v ? 15v w a 2.5v b v out offset gnd dut ad8610 v in f i gure 31. t e s t c i rc uit for g a in v s . f r eq uenc y w b v cm i cm a nc gnd nc v dd dut nc = no connect 04108-0-033 f i g u re 32. t e s t c i rc uit f o r co m m o n -m ode l e ak ag e cur r e n t
ad5162 rev. a | page 13 of 20 theory of operation the ad5162 is a 256-p o si tion dig i t a l l y co n t r o l l ed va r i ab le re s i stor ( v r ) d e v i c e . an in t e r n al p o w e r - o n p r es et places t h e wi p e r a t mids cale d u r i n g p o w e r - on, w h ich sim p l i f i es t h e f a u l t condi t i on r e co v e r y at p o w e r- u p . programming the variable resi stor and voltage r h eos t at ope r ation the n o minal r e sis t a n ce o f t h e rd a c b e tw e e n t e r m inals a and b is a v a i la b l e in 2.5 k?, 10 k?, 50 k?, a nd 100 k?. th e n o minal re s i st anc e ( r ab ) o f th e vr has 2 56 co n t ac t p o in ts acces s e d b y t h e w i p e r t e r m i n al , pl us t h e b ter m inal co n t ac t. the 8- b i t da t a in t h e rd a c l a tc h is deco ded t o s e lec t on e o f the 256 p o s s i b le se t t in g s . a w b a w b a w b 04108-0-034 f i g u re 33. r h e o s t at m o de conf ig ur at i o n a ssu min g t h a t a 10 k? p a r t is us e d , t h e w i p e r s f i rst co nne c t ion s t a r ts a t t h e b t e r m inal fo r da t a 0x00. b e ca us e t h er e is a 50 ? wi p e r co n t ac t r e sist a n ce, such a co nne c t io n y i el ds a mi nim u m o f 100 ? (2 5 0 ?) r e sis t a n ce betw een t e r m inals w an d b . the s e con d co n n e c t i o n is t h e f i rst t a p p o in t, w h ich c o r r esp o n d s t o 139 ? (r wb = r ab /256 + 2 r w = 39 ? + 2 5 0 ?) f o r da ta 0x01. th e t h ird co nne c t io n is t h e n e xt t a p p o in t, r e p r es en t i n g 178 ? (2 39 ? + 2 50 ?) f o r da ta 0x02, an d s o o n . e a c h ls b da ta v a l u e in cr e a s e m o v e s th e wi p e r u p t h e r e sist o r ladder un til th e l a s t ta p p o in t is r e ac h e d a t 1 0 ,100 ? (r ab + 2 r w ). d5 d4 d3 d7 d6 d2 d1 d0 rdac latch and decoder r s r s r s r s a w b 04108-0-035 f i gur e 3 4 . ad51 62 e q ui v a le nt rd a c cir c ui t t h e g e n e ral eq ua ti o n d e t e rm in in g th e d i g i tall y p r ogra m m e d o u t p u t r e s i s t a n ce bet w een w a n d b i s w ab wb r r d d r + = 2 256 ) ( (1) w h er e: d is th e decimal eq ui valen t o f t h e b i na r y co de l o ade d i n t h e 8-b i t rd a c r e g i s t er . r ab is t h e e n d - to -end r e sist an c e . r w i s t h e w i p e r re s i s t a n c e c o n t r i bu t e d by t h e o n re s i s t a n c e of th e in t e rn al swi t c h . i n s u mma r y , if r ab = 10 k? a nd t h e a t e r m ina l is o p en c i rc u i te d, t h e f o l l ow i n g output r e s i st an c e r wb is s e t fo r t h e indic a te d r d a c la tch co des. ta ble 6. c o des a n d corres p o ndi ng r wb resistan ce d (dec) r wb (?) output state 255 9,961 full scale (r ab ? 1 lsb + r w ) 128 5,060 midscale 1 139 1 lsb 0 100 zero scale (wipe r contact resistance) n o t e t h a t , i n t h e zer o -s ca le con d i t io n, a f i ni te wi p e r r e sist a n c e o f 100 ? is p r esen t. c a r e sh o u l d b e ta k e n t o limi t t h e c u r r en t f l o w b e tw e e n w a nd b i n t h is s t a t e t o a maxi m u m p u ls e c u r r en t o f n o m o r e than 20 ma. o t h e r w is e , deg r ada t ion o r p o s s i b le dest r u c t io n o f t h e i n ter n a l s w i t ch co n t ac t can o c c u r . si mi l a r to t h e me ch ani c a l p o te n t i o me te r , t h e re s i st a n c e of t h e rd a c bet w een th e wi per w a n d t e rm i n al a als o p r od uces a dig i t a l l y co n t r o l l ed co m p lem e n t a r y r e sis t a n ce r wa . w h e n t h es e t e r m ina l s a r e us e d , t h e b t e r m in a l ca n b e op e n e d . s e t t in g t h e re s i st anc e v a lu e f o r r wa st ar ts a t a max i m u m v a lu e of re s i st anc e a nd de cr e a s e s a s t h e d a t a lo ade d in t h e la tch i n cr e a s e s in va l u e. the ge n e ra l e q u a t i o n fo r t h is o p era t io n is w ab wa r r d d r + ? = 2 256 256 ) ( (2) fo r r ab = 10 k? a nd t h e b t e r m inal o p en c i r c ui ted , the f o l l ow i n g output re s i st anc e r wa is s e t fo r t h e i n d i ca t e d rd a c la t c h co de s. ta ble 7. co des a nd corr es po n d i n g r wa resist an ce d (dec) r wa (?) output state 255 139 full scale 128 5,060 midscale 1 9,961 1 lsb 0 10,060 zero scale t y p i ca l d e vice -to - de vice ma tchi n g is p r o c ess lo t dep e n d e n t and ma y va r y b y u p t o 30%. b e c a us e t h e r e sis t an ce e l em e n t is p r o c es s e d in thin f i lm t e chn o log y , th e c h a n g e in r ab wi t h t e m p era t ur e has a v e r y lo w 35 p p m/ c t e m p er a t ur e co ef f i cien t.
ad5162 rev. a | page 14 of 20 programming the potentiometer divider voltage o u tp ut ope r ation th e di g i t a l p o te n t i o me te r e a s i ly ge ne r a te s a volt age d i v i de r a t w i p e r - to - b a nd w i p e r - to - a prop or t i ona l to t h e i n put volt age a t a t o b . u n li k e t h e p o la r i ty o f v dd t o gnd , whic h m u s t be p o s i t i ve, volt ag e a c ro ss a to b , w to a , a nd w to b c a n b e a t ei t h er p o la r i ty . a v i w b v o 04108-0-036 f i gure 35. p o tentiometer m o de c o nf ig ur ation i f ig n o r i n g t h e e f fe c t o f t h e w i p e r r e sist a n ce fo r a p p r o x im a t ion, co nne c t in g t h e a ter m ina l to 5 v a nd t h e b ter m ina l to g r o u nd p r o d uces a n ou t p u t v o l t a g e a t the wi p e r - t o -b star tin g a t 0 v u p t o 1 ls b les s than 5 v . e a c h l s b o f v o l t a g e is eq u a l t o th e v o l t - a g e a p plie d acr o ss ter m ina l ab divide d b y t h e 2 56 p o si t i o n s o f t h e p o te n t iom e ter di vi der . t h e gen e r a l e q u a t i o n def i nin g t h e output vo lt ag e at v w wi th r e sp e c t t o g r o u n d f o r a n y valid in p u t v o l t a g e a p plie d t o t e r m ina l s a and b is b a w v d v d d v 256 256 256 ) ( ? + = (3) a m o r e acc u ra te calc u l a t io n, w h ich i n cl udes t h e ef fe c t o f wi p e r re s i st anc e , v w , i s b ab wa a ab wb w v r d r v r d r d v ) ( ) ( ) ( + = (4) o p er a t ion o f t h e dig i t a l p o ten t i o m e ter in t h e divider m o d e re su lt s i n a more a c c u r a te o p e r at i o n ove r te m p e r a t u r e. u n l i ke t h e rh e o s t a t m o de , t h e o u t p u t vol t a g e is de p e n d en t mainl y o n th e ra ti o o f th e in t e rn al r e si s t o r s r wa a nd r wb and n o t t h e a b s o l u t e v a l u es. ther efo r e , t h e tem p er a t ur e dr if t r e d u ces t o 15 p p m /c. esd protection a l l d i g i t a l i n put s are prote c te d w i t h a s e r i e s of i n put re s i stor s a nd p a r a l l el z e n e r es d st r u c t ur es sh o w n i n f i gur e 36 a n d f i gur e 37. this a p p l ies t o t h e dig i tal in p u t p i n s s d i, clk, a nd cs . logic 340 ? gnd 04108-0-037 f i g u re 36. e s d pr ot ec t i o n of d i g i t a l p i ns a, b, w gnd 04108-0-038 f i g u re 37. e s d pr ot ec t i o n of r e s i s t o r t e r m in als terminal voltage operating ra nge the ad5162 v dd an d g n d p o w e r su p p ly def i n e s t h e b o u ndar y c o ndi t i ons for prop e r 3 - te r m i n a l di g i t a l p o te n t i o me te r op e r a - tio n . s u p p l y sig n als p r es en t on t e r m inals a, b , a nd w tha t e x ceed v dd o r gnd a r e clam p e d b y t h e in t e r n al fo r w a r d b i as e d dio d es (s e e f i gu r e 38). gnd a w b v dd 04108-0-039 f i g u re 38. m a x i mu m t e r m i n a l v o lt ag es s e t by v dd and g nd power-up sequence b e ca us e t h e esd p r o t e c t i on dio d es limi t t h e vol t a g e com p li ance a t t e r m in a l s a, b , a nd w (s e e f i gur e 38), i t is im p o r t a n t t o po w e r v dd /gnd bef o r e a p p l yin g a n y v o l t a g e to t e r m i n als a, b , a nd w ; o t h e r w i s e, t h e dio d e is fo r w a r d b i as e d such t h a t v dd is p o w e r e d uni n te n t io na l l y an d m a y a f fe c t t h e r e st o f t h e us er s cir c ui t. t h e id e a l p o w e r - u p s e q u en c e is in t h e fol l o w in g o r der : gnd , v dd , d i g i t a l i n p u t s , a n d t h e n v a , v b , v w . t h e r e l a t i v e o r d e r of p o we r i ng v a , v b , v w , a n d t h e dig i t a l in p u ts is n o t i m p o r t an t as lo n g as t h e y ar e p o w e r e d a f t e r v dd /gnd .
ad5162 rev. a | page 15 of 20 layout and power supply b y passing i t is g o o d p r ac tice t o em p l o y co m p ac t, minim u m lead len g t h la yo u t desig n . th e le ads t o th e in p u ts sh o u ld be as dir e c t as pos s i b le wi th a m i n i m u m co n d uct o r le n g th . g r o u n d p a th s s h o u ld ha v e lo w r e sis t a n ce an d l o w ind u c t an ce . s i mil a rl y , i t is al s o g o o d p r ac tic e t o b y p a s s the p o w e r s u p p lies wi t h q u ali t y ca p a ci t o rs f o r o p tim u m sta b ili t y . s u p p l y leads t o th e de vice s h o u l d b e b y p a s s e d wi th dis c o r c h i p cer a mic c a p a ci t o rs o f 0.01 f t o 0.1 f . l o w es r 1 f t o 10 f ta n t al um o r e l ec tr o- l y tic ca p a ci t o rs s h o u ld als o be a p p l ied a t t h e s u p p lies t o mini mi ze an y t r a n sien t dist urb a n c e an d lo w f r e q uen c y r i p p le (s e e f i gur e 39). n o te t h a t t h e di g i t a l g r o u nd sho u ld a l s o b e j o i n e d re motely to t h e an a l o g g r ou nd a t one p o i n t to mi ni m i z e th e gr o u n d bo un ce . v dd gnd v dd c3 10 f c1 0.1 f ad5162 + 04108-0-040 f i g u r e 3 9 . p o w e r su pp l y by pa s s i n g constant bias to retain resistance setting f o r us ers wh o desir e n o n v ol a t ili t y b u t ca nn ot j u s t if y th e addi - tio n al cos t f o r th e eemem, t h e ad5162 ma y b e co n s ider e d as a lo w cos t al t e rn a t i v e b y m a in ta ini n g a co n s ta n t b i a s t o r e ta i n t h e wi p e r s e t t ing. th e ad5162 is desig n e d s p ecif ic al l y wi th lo w p o w e r in mi nd , w h ich a l lo ws lo w p o w e r co n s u m p t ion e v e n i n b a t t er y-o p era t e d sys t ems. th e g r a p h i n f i gur e 40 dem o n s t r a t e s th e p o w e r co nsum p t ion f r o m a 3.4 v 450 mahr l i -i o n c e l l ph on e b a t t er y , w h ich is co nn e c t e d t o t h e ad51 62. th e m e as ure- m e nt o v e r t i m e s h o w s t h at t h e d e v i c e d r aw s ap p r ox i m at e l y 1.3 a an d con s um es n e g l ig ib le p o w e r . o v er a co urs e o f 30 da ys, t h e b a t t er y is deplet e d b y les s t h a n 2%, t h e ma jo r i ty o f w h ich is d u e t o t h e i n t r in sic le a k a g e c u r r en t o f t h e b a t t er y i t s e lf. t h i s d e m o n s tra t e s th a t co n s ta n t l y b i a s in g t h e p o t e n t i o m e t e r i s n o t an i m p r ac t i ca l a p p r o a ch. m o st p o r t a b le d e v i ces do n o t r e q u ir e t h e r e mo val o f b a t t er ies fo r t h e p u r p os e o f cha r g i n g . al th o u g h the r e sis t a n ce s e t t in g o f th e ad5162 is los t when t h e ba t t e r y n e e d s r e p l a c em en t , s u c h ev e n t s occur ra th e r i n f r e- q u en t l y such t h a t t h is i n con v en ien c e is j u st if ie d b y t h e lo w e r cos t a nd smal ler size o f f e r e d b y th e ad5162. i f a nd w h en t o t a l p o w e r is los t , t h e us er s h o u ld b e p r o v ide d w i t h a me a n s t o ad j u st t h e s e t t i n g acco r d in g l y . days battery life depleted 0 90% 92% 94% 96% 51 0 1 5 98% 100% 102% 104% 106% 108% 110% 20 25 30 04108-0-041 t a = 25 c f i gure 4 0 . ba tter y o p er a t i n g li fe d e p l etio n evaluation board a n e v a l u a t i on b o ard, a l ong w i t h a l l ne c e ss ar y s o f t w a re, i s a v a i la b l e t o p r og ra m the ad51 62 f r o m a n y pc r u nnin g w i n d o w s 98/20 00/xp . th e g r a p hical us er in t e r f ace , as sh o w n in f i gur e 41, is st r a ig h t fo r w a r d and e a sy to us e. m o r e det a i l e d info r m a t io n is a v a i lab l e in t h e u s er ma n u a l , w h i c h com e s wi t h th e boa r d . f i g u re 41. a d 5 1 6 2 ev aluat i on bo ar d s o f t w a r e the ad5162 s t ar ts a t mids cale u p o n p o w e r - u p . t o in cr em en t or de cr em e n t t h e resis t a n ce , t h e us er ma y sim p l y m o v e t h e s c r o l l - b a rs o n t h e lef t . t o wr i t e an y sp e c if ic val u e , t h e us er s h o u ld us e t h e b i t p a t t er n in t h e u p p e r s c r e en an d p r es s t h e r u n b u t t on. the fo r m a t o f wr i t i n g da t a t o t h e de vice is sh o w n in t a b l e 8.
ad5162 rev. a | page 16 of 20 spi interface spi compatible 3-wire serial bus the ad5162 con t a i n s a 3 - wir e s p i co m p a t ib le dig i t a l in t e r f ace (s d i , cs , a n d c l k ) . t h e 9 - b i t s e r i a l w o r d m u s t b e l o a d e d m s b f i rs t. the fo r m a t o f t h e w o r d is s h own i n t a b l e 8. the p o si t i ve-e dg e s e n s i t i v e cl k in p u t r e q u ir e s cle a n t r a n si t i on s to a v o i d clo c k i ng in co r r e c t da t a in to t h e s e r i a l i n p u t r e g i ster . s t a nda rd log i c fa milies w o rk w e l l . i f m e c h a n ical swi t ch es a r e us ed f o r p r o d uc t eval ua tio n , t h e y s h o u ld be deb o un ce d b y a f l ip - f l o p or ot he r su it abl e me an s . w h e n cs is lo w , t h e clo c k lo ads da t a in t o t h e s e r i al r e g i s t er o n eac h p o si t i v e c l o c k edge (s ee f i gur e 42). the da t a s e t u p a nd da t a h o ld t i m e s i n t h e sp e c i f ica t ion t a b l e det e r m in e t h e valid timin g r e q u ir em en ts. the ad5162 us es a 9 - bit s e r i a l i n p u t d a t a re g i ste r w o rd t h a t i s t r ans f e r re d to t h e in t e r n al rd a c r e g i s t er w h en the cs line r e t u r n s to log i c hig h . e x t r a m s b b i t s are i g nore d. table 8. serial data-word fo rmat b 8 b 7 b 6 b 5 b 4 b 3 b 2 b 1 b 0 a 0 d 7 d 6 d 5 d 4 d 3 d 2 d 1 d 0 m s b l s b 2 8 2 7 2 0 sdi clk cs v out rdac register load a0 d7 d6 d5 d4 d3 d2 d1 d0 0 1 0 1 0 0 1 1 04108-0-042 f i g u re 42. spi inte r f ac e ti m i ng d i ag r a m (v a = 5 v , v b = 0 v , v w = v ou t ) t csho t css t cl t ch t ds t csw t s t cs1 t csh1 t ch clk cs v out 1 0 1 0 1 0 v dd 0 1lsb sdi (data in ) dx dx 04108-0-043 f i gure 43. spi inte r f ac e d e tai l ed tim i n g d i ag r a m ( v a = 5 v , v b = 0 v , v w = v ou t )
ad5162 rev. a | page 17 of 20 outline dimensions 0.23 0.08 0.80 0.60 0.40 8 0 0.15 0.00 0.27 0.17 0.95 0.85 0.75 seating plane 1.10 max 10 6 5 1 0.50 bsc 3.00 bsc 3.00 bsc 4.90 bsc pin 1 coplanarity 0.10 compliant to jedec standards mo-187ba f i gure 44. 1 0 -l ead m i ni s m al l o u tl ine p a ck ag e [msop ] (r m - 10) di me nsio ns sho w n i n mi ll im e t e r s ordering guide m o d e l r ab (?) temperature package descri ption package option branding ad5162brm2.5 2.5 k C40c to +125c msop-10 rm-10 d0q ad5162brm2.5- rl7 2.5 k C40c to +125c msop-10 rm-10 d0q ad5162brm10 10 k C40c to +125c msop-10 rm-10 d0r ad5162brm10- rl7 10 k C40c to +125c msop-10 rm-10 d0r ad5162brm50 50 k C40c to +125c msop-10 rm-10 d0s ad5162brm50- rl7 50 k C40c to +125c msop-10 rm-10 d0s ad5162brm100 100 k C40c to +125c msop-10 rm-10 d0t ad5162brm100 -rl7 100 k C40c to +125c msop-10 rm-10 d0t ad5162eval see note 1 evaluation boar d 1 th e evaluat i on board is s h ippe d with the 10 k ? r ab re si st or opt i on ; h o w e ver, t h e boa r d i s com p a t i b le wi t h a ll a v a i l a b le r e si st or va lu e opt i on s.
ad5162 rev. a | page 18 of 20 notes
ad5162 rev. a | page 19 of 20 notes
ad5162 rev. a | page 20 of 20 notes ? 2003 analo g de vices, inc. all rights reserve d . tra d em arks and registered tra d ema r ks are the prop erty of their respective owners . c04108C0 C 11/03(a)

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