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lf to 2.5 ghz trupwr? detector ad8361 rev. c 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 . s p ecificatio n s subj ec t to ch an 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 ? 2004 analog de vices, i n c. al l r i ght s r e ser v ed . fea t ures calibrated rms response excellent temp erature s t abilit y up to 30 db inp u t range at 2.5 ghz 700 mv rms, 1 0 dbm, re 5 0 ? maximum inpu t 0.25 db linear response up to 2.5 g hz single-supply operation: 2.7 v to 5.5 v low power: 3.3 mw at 3 v sup p ly rapid power-down to less than 1 a applic a t io ns measurement of cdma, w-cdma, qam, ot her complex modulation wa veforms rf transmitter or receiver power measurem ent gener a l description the ad8361 is a mea n -r es p o ndin g p o w e r det e c t o r f o r us e in hig h f r e q ue n c y r e cei v er an d t r an smi t t e r sig n a l cha i n s , u p t o 2.5 gh z. i t is v e r y easy t o a p p l y . i t r e q u ir es a sing le s u p p l y o n l y betw een 2.7 v and 5.5 v , a p o w e r s u p p l y deco u p lin g c a p a ci t o r , a nd an in p u t cou p lin g c a p a ci t o r in m o st a p plic a t io n s . t h e o u t p ut is a li n e ar -r esp o n d i n g dc vol t a g e wi t h a c o n v ersio n ga i n o f 7.5 v/v r m s. an ext e r n al f i l t er ca p a ci t o r can be adde d t o i n cr ease t h e a v era g i n g tim e co n s ta n t . rfin (v rms) 3.0 1.6 0 0.5 0.1 0.2 0.3 0.4 2.6 2.2 2.0 1.8 2.8 2.4 v rms (v ol ts ) 1.4 1.2 1.0 0.6 0.8 0.4 0.2 0.0 supply reference mode internal reference mode ground reference mode 01088-c-001 f i gure 1. o u tput i n the th r e e r e ference mod e s, sup p l y 3 v , f r equ e nc y 1.9 g h z (6-l ead s o t - 23 p a c k age g r ou nd r e fe renc e m o de o n ly) func ti on a l bl ock di a g r a ms rfin iref pwdn vpos fltr sref vrms comm band-gap reference error amp ad8361 internal filter add offset trans- conductance cells i i 7.5 buffer 2 2 01088-c - 002 f i g u re 2. 8-l e ad m s op rfin iref pwdn vpos fltr vrms comm band-gap reference error amp ad8361 internal filter trans- conductance cells i i 7.5 buffer 2 2 01088-c - 003 f i g u re 3. 6-l e ad s o t - 23 the ad8361 is in t e n d ed f o r tr ue p o w e r m e as ur em en t o f sim p le a nd com p lex wa v e f o r m s. th e de vice is p a r t ic u l arl y us ef u l f o r m e as ur in g hig h cr es t-fac t o r (hig h p e a k -t o-r m s ra tio) sig n als, s u ch as cd m a a nd w - cd m a . the ad8361 has thr e e o p era t ing m o des t o accommo da te a va r i ety o f a n alog-t o-dig i t a l co n v er t e r r e q u ir emen ts: 1. gr o u n d r e fer e nce mo de , i n w h i c h t h e o r ig in is zer o . 2. i n t e r n al r e f e r e nce mo de , w h ic h o f fs ets th e o u t p u t 350 mv ab ove g r ou n d . 3. s u p pl y r e fer e n c e m o de , w h ich o f fs ets t h e o u t p u t t o v s /7.5. the ad8361 is s p ecif ie d f o r o p era t io n f r o m ?4 0c t o +85c a nd is a v a i lab l e in 8-lead mso p a nd 6-lead sot - 23 p a c k a g es. i t is fa b r ica t e d o n a p r o p r i et a r y hig h f t silico n b i p o la r p r o c es s.
ad8361 rev. c | page 2 of 24 table of contents specifications ..................................................................................... 3 absolute maximum ratings ............................................................ 4 esd caution .................................................................................. 4 pin configuration and function descriptions ............................. 5 typical performance characteristics ............................................. 6 circuit description ......................................................................... 11 applications ..................................................................................... 12 output reference temperature drift compensation ........... 16 evaluation board ............................................................................ 21 characterization setups ............................................................. 23 outline dimensions ....................................................................... 24 ordering guide .......................................................................... 24 revision history 8/04data sheet changed from rev. b to rev. c. changed trimpots to trimmable potentiometers .........universal changes to specifications ................................................................ 3 changed using the ad8361 section title to applications ....... 12 changes to figure 43...................................................................... 14 changes to ordering guide .......................................................... 24 updated outline dimensions ....................................................... 24 2/01data sheet changed from rev. a to rev. b.
ad8361 rev. c | page 3 of 24 specifications t a = 25c, v s = 3 v, f rf = 900 mhz, ground reference output mode, unless otherwise noted. table 1. parameter condition min typ max unit signal input interface (input rfin) frequency range 1 2.5 ghz linear response upper limit v s = 3 v 390 mv rms equivalent dbm, re 50 ? 4.9 dbm v s = 5 v 660 mv rms equivalent dbm, re 50 ? 9.4 dbm input impedance 2 225||1 ?||pf rms conversion (input rfin to output v rms) conversion gain 7.5 v/v rms f rf = 100 mhz, v s = 5 v 6.5 8.5 v/v rms dynamic range error referred to best fit line 3 0.25 db error 4 cw input, ?40c < t a < +85c 14 db 1 db error cw input, ?40c < t a < +85c 23 db 2 db error cw input, ?40c < t a < +85c 26 db cw input, v s = 5 v, ?40c < t a < +85c 30 db intercept-induced dynamic internal reference mode 1 db range reduction 5 , 6 supply reference mode, v s = 3.0 v 1 db supply reference mode, v s = 5.0 v 1.5 db deviation from cw response 5.5 db peak-to-average ratio (is95 reverse link) 0.2 db 12 db peak-to-average ratio (w-cdma 4 channels) 1.0 db 18 db peak-to-average ratio (w-cdma 15 channels) 1.2 db output intercept 5 inferred from best fit line 3 ground reference mode (grm) 0 v at sref, v s at iref 0 v f rf = 100 mhz, v s = 5 v ?50 +150 mv internal reference mo de (irm) 0 v at sref, iref open 350 mv f rf = 100 mhz, v s = 5 v 300 500 mv supply reference mode (srm) 3 v at iref, 3 v at sref 400 mv v s at iref, v s at sref v s /7.5 v f rf = 100 mhz, v s = 5 v 590 750 mv power-down interface pwdn hi threshold 2.7 v s 5.5 v, ?40c < t a < +85c v s ? 0.5 v pwdn lo threshold 2.7 v s 5.5 v, ?40c < t a < +85c 0.1 v power-up response time 2 pf at fltr pin, 224 mv rms at rfin 5 s 100 nf at fltr pin, 224 mv rms at rfin 320 s pwdn bias current <1 a power supplies operating range ?40c < t a < +85c 2.7 5.5 v quiescent current 0 mv rms at rfin, pwdn input lo 7 1.1 ma power-down current grm or irm, 0 mv rm s at rfin, pwdn input hi <1 a srm, 0 mv rms at rfin, pwdn input hi 10 v s a 1 operation at arbitrarily low frequencies is possible; see ap section. plications applications 2 figure 17 and figure 47 show imped ance versus frequency for the msop and sot-23, respectively. 3 calculated using linear regression. 4 compensated for output reference temperature drift; see section. 5 sot-23-6l operates in ground reference mode only. 6 the available output swing, and hence the dynamic range, is al tered by both supply voltage an d reference mode; see figure 39 a nd figure 40. 7 supply current is input leve l dependant; see figure 16.
ad8361 r e v. c | pa ge 4 o f 2 4 absolute maximum ra tings table 2. p a r a m e t e r r a t i n g supply voltage v s 5.5 v sref, pwdn 0 v, v s i r e f v s ? 0.3 v, v s rfin 1 v rms equivalent power, re 50 ? 13 dbm internal power dissip a tion 1 200 mw 6-lead sot-23 170 mw 8-lead msop 200 mw maximum junction temperature 125c operating temperature range ?40c to +85c storage temperature range ?65c to +150c lead temperature range (sol dering 60 s e c) 300c 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 . 1 specif ication is f o r the d e vice in f r ee ai r. 6-lead sot-23: ja = 230c/w; jc = 92 c/w. 8-lead msop: ja = 200c/w; jc = 44 c/w . esd c a ution 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.
ad8361 r e v. c | pa ge 5 o f 2 4 pin conf igura t ion and fu nction descriptions vpos 1 iref 2 rfin 3 pwdn 4 sref 8 vrms 7 fltr 6 comm 5 ad8361 top view (not to scale) 01088-c-004 f i g u re 4. 8-l e ad m s op vrms 1 comm 2 fltr 3 vpos 6 rfin 5 pwdn 4 ad8361 top view (not to scale) 01088-c-005 f i g u re 5. 6-l e ad s o t - 23 ta ble 3. pi n f u nct i on d e s c ri pt i o ns pin no. msop pin no. s o t - 2 3 m n e m o n i c d e s c r i p t i o n 1 6 vpos supply voltage pin. operational range 2.7 v to 5 . 5 v. 2 n/a iref output referen c e control pin. i n tern al referen c e mode enabled when pi n i s left open; other w ise , this pin shou ld be tied to vpos. do not ground this pin. 3 5 rfin signal input pin. must be driven from an ac-cou p l ed source. the low freque ncy real input impedance is 225 ?. 4 4 pwdn power-dow n pin. for the d evice to operate as a d e tector, it need s a logica l lo w input ( l ess tha n 100 mv). when a logic high (gre ater than v s ? 0.5 v) is applied, the devi ce is turned off and the s u pply current goes to nearly zero (g round and internal reference mod e less tha n 1 a, supply referenc e mode v s divide d by 100 k?). 5 2 comm device ground pin. 6 3 fltr by placing a c a p a citor between t h is pin a n d vpos, th e corner frequency of the modulation filter is lowered . t h e on -chip filter is for m ed with 27 pf||2 k? for small i n put signals. 7 1 vrms output pin. nea r rail-to-rai l volt age output with limited current drive capabi litie s . expected load >10 k? to ground. 8 n/a sref supply referenc e control pin. to en ab le supp ly reference mod e , this pin must be connected to vpos; otherw is e, it s h oul d be connect ed to comm (gr o und).
ad8361 r e v. c | pa ge 6 o f 2 4 typical perf orm ance cha r acte ristics input (v rms) 2.8 2.6 0.8 0 0.5 0.1 0.2 0.3 0.4 2.0 1.4 1.2 1.0 2.4 2.2 1.6 1.8 output ( v ) 0.6 0.4 0.2 0.0 900mhz 100mhz 1900mhz 2.5ghz 01088-c-006 f i gur e 6 . output vs . input l e v e l , f r e q uenc ie s 10 0 mhz, 900 mhz , 19 00 m h z , a n d 25 0 0 m h z, su p p ly 2. 7 v , ground r e f e r e nc e m o d e , m s o p input (v rms) 5.5 1.5 0 0.5 0.1 0.2 0.3 0.4 4.0 3.0 2.5 2.0 5.0 4.5 3.5 output ( v ) 1.0 0.5 0.0 5.5v 5.0v 3.0v 2.7v 0.6 0.7 0.8 01088-c-007 f i gure 7 . o u tput vs . input l e v e l , sup p ly 2.7 v , 3 . 0 v , 5.0 v , and 5. 5 v , f r e q uenc y 9 0 0 m h z input (v rms) 5.0 1.5 0 0.5 0.1 0.2 0.3 0.4 4.0 3.0 2.5 2.0 4.5 3.5 output ( v ) 1.0 0.5 0.0 0.6 0.7 0.8 cw is95 reverse link wcdma 4- and 15-channel 01088-c-008 f i gure 8 . o u tput vs . input l e v e l wi th d i f f e r e nt w a vef o r m s si ne w a ve (c w ) , is9 5 r e ve rs e l i nk , w - cdma 4- chan n e l and w - cdma 15- channel , su p p ly 5. 0 v input (v rms) 3.0 2.5 ? 1.0 0.4 (+5dbm) 0.01 1.5 0 ? 0.5 2.0 0.5 1.0 e r ror (db) ? 1.5 ? 2.0 ? 2.5 ? 3.0 0.1 ( ? 7dbm) 0.02 (?21dbm) mean 3 sigma 01088-c-009 f i gure 9. e r r o r fro m line ar r e ference v s . input l e vel , 3 sig m a to e i the r sid e o f m e an, sin e w a v e , s u p p ly 3.0 v , f r eque nc y 90 0 m h z input (v rms) 3.0 2.5 ? 1.0 0.6 (+8.6dbm) 0.01 1.5 0 ? 0.5 2.0 0.5 1.0 e rror (db) ? 1.5 ? 2.0 ? 2.5 ? 3.0 0.1 0.02 mean 3 sigma ( ? 7dbm) ( ? 21dbm) 01088-c-010 f i gure 10. e rror f r o m li ne ar r e f e renc e v s . input l e vel , 3 si gma to e i ther sid e of me an, s i ne w a ve , su p p ly 5. 0 v , f r e q uenc y 9 0 0 mh z input (v rms) 3.0 2.5 ? 1.0 1.0 0.01 0.1 1.5 0.0 ? 0.5 2.0 0.5 1.0 e rror (db) ? 1.5 ? 2.0 ? 2.5 ? 3.0 0.02 0.6 0.2 is95 reverse link cw 15-channel 4-channel 01088-c-011 f i gure 11. e rror f r o m c w lin e a r r e fe renc e v s . input with d i ffer e nt w a vefo r m s sine w a ve (c w ) , is 95 r e vers e l i nk , w - cdm a 4- chann e l a n d w - cdm a 1 5 - c han n el , sup p l y 3. 0 v , f r equenc y 90 0 m h z
ad8361 r e v. c | pa ge 7 o f 2 4 3.0 2.5 ?1.0 0.4 (+5dbm) 0.01 1.5 0 ?0.5 2.0 0.5 1.0 e rror (db) ?1.5 ?2.0 2.5 ?3.0 0.1 0.02 mean 3 sigma input (v rms) (?7dbm) (?21dbm) 01088-c-012 f i gure 12. e rror f r o m c w lin e a r r e fe renc e v s . input, 3 s i g m a to e i the r sid e o f m e an, is9 5 r e ve rs e link s i g n a l , su p p ly 3. 0 v , f r equ e nc y 9 00 m h z input (v rms) 3.0 2.5 ?1.0 0.6 (+8.6dbm) 0.01 1.5 0 ?0.5 2.0 0.5 1.0 e rror (db) ?1.5 ?2.0 ?2.5 ?3.0 0.1 0.02 mean 3 sigma (?7dbm) (?21dbm) 01088-c-013 f i gure 13. e rror f r o m c w lin e a r r e fe renc e v s . input l e ve l , 3 s i gm a to e i ther side of m e an, is9 5 r e vers e li nk sig n al , sup p l y 5. 0 v , f r eq uenc y 9 0 0 m h z input (v rms) 3.0 2.5 ?1.0 0.4 (+5dbm) 0.01 1.5 0 ?0.5 2.0 0.5 1.0 e rror (db) ?1.5 ?2.0 ?2.5 ?3.0 0.1 0.02 ?4 0 c +85 c (?7dbm) (?21dbm) 01088-c-014 f i g u re 14. o u t p ut d e lt a f r o m +2 5c v s . input l e vel , 3 sig m a to either side of m e an sin e w a ve , su p p ly 3.0 v , f r equ e nc y 90 0 m h z, t e mper at ur e ? 4 0 c to + 8 5 c input (v rms) 3.0 2.5 ? 1.0 0.4 (+5dbm) 0.01 1.5 0 ? 0.5 2.0 0.5 1.0 e rror (db) ? 1.5 ? 2.0 ? 2.5 ? 3.0 0.1 0.02 ( ? 7dbm) (?21dbm) ?40 c +85c 01088-c-015 f i g u re 15. o u t p ut d e lt a f r o m +2 5c v s . input l e vel , 3 sig m a to e i t h e r side of me an s i n e w a v e , su p p ly 3.0 v , f r eq uenc y 19 0 0 m h z, t e m p er ature ? 4 0 c to +8 5c input (v rms) 11 3 0 0.5 0.1 0.2 0.3 0.4 8 6 5 4 10 9 7 s u p p l y curre nt (ma) 2 1 0 0.6 0.7 0.8 +85 c ?4 0 c +25c v s = 5v input out of range +25 c +85 c ?40 c v s = 3v input out of range 01088-c-016 f i g u re 16. sup p l y current v s . input l e vel , s u p p l i es 3. 0 v , a n d 5. 0 v , t e m p er atures ? 4 0 c, +2 5c , a n d + 8 5 c frequency (mhz) 0 500 1000 250 200 150 s hunt re s i s t ance ( ? ) 100 50 0 2000 2500 1.4 1.2 1.0 s hunt cap acitance (pf) 0.8 0.6 0.4 1500 +85 c +25 c ?40 c +85 c +25 c ?4 0 c 1.6 1.8 01088-c-017 f i gure 17. input i m pedance v s . f r eque nc y , sup p ly 3 v , t e m p er atures ? 4 0 c, +2 5c , a n d + 8 5 c, msop (s ee a p p l ic at i o ns f o r s o t - 23 d a t a )
ad8361 r e v. c | pa ge 8 o f 2 4 temperature (c) ? 0.02 40 ? 4 0 ? 20 0 2 0 0.03 0.01 0.00 ? 0.01 0.02 inte rce p t change (v ) ? 0.03 ? 0.04 ? 0.05 60 80 100 mean 3 sigma 01088-c-018 f i gure 18. o u tput r e ferenc e cha n ge v s . t e mpe r atu r e , sup p ly 3 v , g r ou nd refer e nc e mod e temperature (c) ?0.01 40 ? 4 0 ? 20 0 2 0 0.02 0.01 0.00 inte rce p t change (v ) ?0.02 ?0.03 60 80 100 mean 3 sigma 01088-c-019 f i gure 19. o u tput referenc e cha n ge v s . t e mpe r atu r e , su p p ly 3 v , int e rn al refer e nce mode (mso p o n l y ) temperature (c) ? 0.02 40 ? 4 0 ? 20 0 2 0 0.03 0.01 0.00 ? 0.01 0.02 inte rce p t change (v ) ? 0.03 ? 0.04 ? 0.05 60 80 100 mean 3 sigma 01088-c-020 f i gure 20. o u tput referenc e cha n ge v s . t e mpe r atu r e , su p p ly 3 v , sup p ly refe r e nc e mode (mso p o n ly) temperature (c) 0.02 40 ? 4 0 ? 20 0 2 0 0.12 0.08 0.06 0.04 0.10 gain change (v /v rms ) 0.00 ? 0.02 ? 0.04 60 80 100 mean 3 sigma ? 0.06 0.14 0.16 0.18 01088-c-021 f i gure 21. co n v ersi on g a in cha n ge v s . t e mpe r atu r e , sup p ly 3 v , gr ou nd r e fe r e nce mode , f r eque nc y 9 00 m h z temperature (c) 0.02 40 ? 4 0 ? 20 0 2 0 0.12 0.08 0.06 0.04 0.10 gain change (v /v rms ) 0.00 ? 0.02 ? 0.04 60 80 100 mean 3 sigma ? 0.06 0.14 0.16 0.18 01088-c-022 f i gure 22. co n v ersi on g a in cha n ge v s . t e mpe r atu r e , sup p ly 3 v , intern a l r e fe r e nce mode , f r eque nc y 9 00 m h z (msop o n l y ) temperature (c) 0.02 40 ? 4 0 ? 20 0 2 0 0.12 0.08 0.06 0.04 0.10 gain change (v /v rms ) 0.00 ? 0.02 ? 0.04 60 80 100 mean 3 sigma ? 0.06 0.14 0.16 0.18 01088-c-023 f i gure 23. co n v ersi on g a in cha n ge v s . t e mpe r atu r e , sup p ly 3 v , sup p ly r e fe r e nc e mode , f r eque nc y 9 00 m h z (msop o n l y )
ad8361 r e v. c | pa ge 9 o f 2 4 67mv 370mv 270mv 25mv 5 s per horizontal division gate pulse for 900mhz rf tone rf input 500mv per vertical division 01088-c-024 f i gure 24. o u tput resp onse t o m o du lat e d p u lse input for v a rious rf inp u t l e vels, sup p ly 3 v , m o dul a t i on f r equ e nc y 90 0 m h z, no f i lte r cap a c i t o r 67mv 370mv 25mv 500mv per vertical division 50 s per horizontal division rf input ga t e p u l s e f or 900m h z r f t o n e 270mv 01088-c-025 f i gure 25. o u tput resp onse t o m o du lat e d p u lse input for v a rious rf inp u t l e vels, sup p ly 3 v , m o dul a t i on f r equ e nc y 90 0 m h z, 0. 01 f f i lter cap a c i t o r r1 75 ? 0.1 f hpe3631a power supply c4 0.01 f c2 100pf hp8648b signal generator c1 c3 tek tds784c scope c5 100pf tek p6204 fet probe 1 2 3 4 8 7 6 5 ad8361 vpos iref rfin pwdn sref vrms fltr comm 01088- c- 026 f i gure 26. h a r d w a re co nfigur ati o n fo r o u tput resp o n se to mo d u la t e d p u l s e input rf input 67mv 370mv 270mv 25mv 500mv per vertical division pwdn input 2 s per horizontal division 01088-c-027 f i gure 27. o u tput r e s p ons e u s i n g p o wer - d o wn mod e fo r v a ri ous r f inp u t l e vels, sup p ly 3 v , f r equ e nc y 9 0 0 m h z, no f i lte r cap a c i t o r 67mv 370mv 270mv 25mv 500mv per vertical division pwdn input rf input 01088-c-028 20 s per horizontal division f i gure 28. o u tput r e s p ons e u s i n g p o wer - d o wn mod e fo r v a ri ous r f inp u t l e vels, sup p ly 3 v , f r equ e nc y 9 0 0 m h z, 0. 01 f f i lt er capa cit o r r1 75 ? 0.1 f hpe3631a power supply c4 0.01 f c2 100pf hp8648b signal generator hp8110a signal generator c1 c3 tek tds784c scope c5 100pf tek p6204 fet probe 1 2 3 4 8 7 6 5 ad8361 vpos iref rfin pwdn sref vrms fltr comm 01088- c- 029 f i gure 29. h a r d w a re co nfigur ati o n fo r o u tput resp onse usi n g p o w e r - d o wn mo d e
ad8361 rev. c | page 10 of 24 carrier frequency (mhz) 7.8 7.6 6.2 100 1000 7.2 6.6 6.4 7.4 6.8 7.0 conversion gain ( v /v rms) 6.0 5.8 5.6 v s = 3v 01088-c-030 f i g u re 30. co nvers i on g a in cha n g e v s . f r eq uenc y , su p p ly 3 v , g r ound r e f e r e n c e m o d e , f r equenc y 10 0 m h z t o 2 5 00 m h z, r e pre s ent a t i ve d e v i c e 67mv 370mv 270mv 25mv 500mv per vertical division supply 20 s per horizontal division rf input 01088-c-031 f i gure 31. o u tput r e s p ons e to g a ting on p o w e r su p p ly , f o r v a r i ous r f i n put l e vels, sup p ly 3 v , m o dul a t i on f r equ e nc y 90 0 m h z, 0. 01 f f i lter cap a c i t o r r1 75 ? 732 ? 50 ? 0.1 f c4 0.01 f c2 100pf hp8648b signal generator c1 c3 tek tds784c scope c5 100pf tek p6204 fet probe 1 2 3 4 8 7 6 5 ad8361 vpos iref rfin pwdn sref vrms fltr comm 01088-c-032 hp8110a pulse generator ad811 f i gure 32. h a r d w a re co nfigur ati o n fo r o u tput r e s p ons e to p o w e r sup p l y ga ti n g me a s ur em en ts conversion gain (v/v rms) 7.6 6.9 7.0 7.2 16 p e rce nt 7.4 7.8 14 12 10 8 6 4 2 0 01088-c-033 f i g u re 33. co nvers i on g a in d i s t r i but i o n f r equenc y 1 00 m h z, sup p ly 5 v , s a mpl e size 30 00 iref mode intercept (v) 0.40 0.32 0.34 0.36 per c e n t 0.38 0.44 12 10 8 6 4 2 0 0.42 01088-c-034 f i gure 34. o u tput r e ference , in ter n a l r e ferenc e mod e , s u p p ly 5 v , s a mpl e si ze 3 0 00 ( m sop o n ly) sref mode intercept (v) 0.72 0.64 0.66 0.68 p e rce nt 0.70 0.76 12 10 8 6 4 2 0 0.74 01088-c-035 f i gure 35. o u tput reference , su p p ly re fer e n c e m o d e , su p p ly 5 v , s a mpl e si ze 3 0 00 ( m sop o n ly)
ad8361 rev. c | page 11 of 24 circuit description the ad8361 is a n r m s-r e s p ondin g (mea n p o w e r) det e c t o r tha t p r o v ides a n a p pr o a ch t o t h e exac t m e as ur e m en t o f rf p o w e r t h a t is b a si ca l l y indep e n d en t o f wa v e fo r m . i t achie v es t h is f u n c t i on t h r o ug h t h e us e o f a p r o p r i et a r y t e chniq u e in w h ich th e o u t p u t s o f tw o i d e n tical sq ua ri n g ce lls a r e bala n c e d b y th e a c t i on of a h i g h - g ai n e r ror am p l i f i e r . the sig n al t o b e m e as ur e d is a pplie d t o t h e i n pu t o f t h e f i rs t s q u a r i ng c e l l , w h i c h pre s e n t s a nom i n a l ( l f ) re s i st an c e of 225 ? between th e rfi n an d c o mm p i n s (conn e c t e d t o the g r o u n d pl an e). b e ca us e t h e in pu t p i n is a t a b i a s vol t a g e o f ab ou t 0.8 v a b o v e g r o u nd , a co u p ling ca p a c i t o r is r e q u ir ed . b y making t h is a n ext e r n al co m p on e n t, t h e m e as ur e m en t ra n g e ma y b e e x te nd e d to ar bi t r ar i l y l o w f r e q u e nc i e s . the ad8361 r e s p on ds t o t h e vol t a g e , v in , a t i t s i n p u t b y sq u a ri n g th i s v o l t a g e t o g e n e ra t e a cu rr e n t p r o p o r ti o n al t o v in s q ua r e d . this is a p plie d t o an in t e r n a l lo ad r e sist o r , acr o ss w h ich a c a p a ci t o r is conn e c t e d . th es e fo r m a lo w-p a s s f i l t er , w h ich e x tra c t s th e m e a n o f v in sq u a r e d . al t h o u gh e s s e n t i a ll y v o l t a g e- r e s p o nding, t h e as s o c i a t e d in p u t im p e dan c e c a lib r a t es t h is p o r t in t e r m s o f e q uivalen t p o w e r . th er efo r e , 1 mw co r r es p o n d s t o a v o l t a g e in p u t o f 447 mv r m s. th e a p p l ic a t io n s s e c t io n sh o w s how to m a tch t h i s i n put to 5 0 ? . the v o l t a g e acr o s s t h e lo w-p a s s f i l t er , w h os e f r e q uen c y ma y b e a r b i t r a r i l y lo w , is a p plie d t o on e in p u t o f an er r o r - s e n s i n g a m plif ier . a s e c o nd ide n t i ca l v o l t a g e - s q ua r i n g c e l l is us e d t o clos e a nega t i v e fe e d b a ck lo o p ar o u n d t h is er r o r a m plif ier . this s e con d c e l l is dr i v en b y a f r ac tion o f th e q u asi-dc o u t p u t v o l t a g e o f th e ad8361. w h en t h e v o l t ag e a t t h e in p u t of th e s e cond s q ua r i n g c e l l is eq ual t o t h e r m s val u e o f v in , t h e l o o p i s i n a s t a b le st a t e , an d t h e o u t p ut t h en r e p r es en ts t h e r m s val u e o f t h e in p u t. th e f e e d bac k ra tio is n o minal l y 0.133, makin g t h e r m s - dc co n v ersio n gain 7.5, t h a t is rms v v in out = 5 . 7 b y c o m p l e t i n g th e f e ed b a c k pa th t h r o u g h a se co n d s q ua ri n g ce l l , iden t i cal t o t h e on e r e ce iving t h e sig n al t o b e m e as ur e d , s e v e ral b e n e f i t s a r is e . f i rs t, s c ali n g ef fe c t s in t h e s e ce l l s can c e l ; th us , th e o v e r all cali b r a t i o n ma y be a c cura t e , ev en th o u g h t h e op e n - l o o p re s p ons e of t h e s q u a r i ng c e l l s t a ke n s e p a r a t e ly ne e d n o t be . n o t e tha t i n im p l em en tin g rm s - d c co n v e r s i o n , n o r e fer e n c e v o l t a g e en t e rs i n t o t h e clos e d -lo o p s c a l in g. s e co nd , t h e t r a c k i ng i n t h e re sp ons e s of t h e d u a l c e l l s re m a i n s ve r y cl o s e o v er t e m p era t ure , le adin g t o exce l l en t st a b i l i t y o f cali b r a t ion. the s q ua r i n g cel l s ha v e v e r y wide ban d wid t h wi th an in tr in sic re sp ons e f rom d c to m i c row a v e. h o we ve r , t h e dy n a m i c r a nge of s u c h a sys tem is fa ir l y smal l , d u e in p a r t t o the m u c h l a r g er d y na mic ran g e a t t h e o u t p ut o f t h e s q ua r i n g c e l l s. th er e a r e pr a c t i c a l l i m i t a t i ons to t h e a c c u r a c y of s e ns i n g ve r y s m a l l e r ror sig n als a t t h e b o t t o m en d o f t h e d y na mic ra n g e , a r isin g f r o m smal l ra n d o m o f fs ets tha t limi t t h e a t t a ina b le a ccura c y a t smal l in p u ts. on the o t h e r hand , th e s q ua r i ng ce l l s in t h e ad8361 ha v e a c l as s - ab as p e c t ; t h e p e a k i n p u t is n o t li mi t e d b y t h eir q u ies c en t b i as co n d i t io n b u t is det e r m in e d ma inl y b y th e ev en t u al los s o f s q u a re - l a w c o n f or m a nc e. c o ns e q u e n t ly , t h e top e n d of t h e i r r e s p o n s e ra n g e o c c u rs a t a fairly la rg e in p u t l e ve l (a p p r o x ima tely 700 mv r m s) w h ile p r es er vin g a r e as o n a b l y acc u ra t e s q ua r e -la w r e s p o n s e . t h e m a x i m u m u s a b l e r a n g e i s , i n p r a c t i c e , l i m i t e d b y th e o u t p u t swin g. th e ra il-t o-rail o u t p u t s t a g e ca n swin g f r o m a f e w mil l i v ol ts abo v e g r o u nd t o les s tha n 100 mv b e lo w th e s u p p ly . an exam ple o f t h e o u t p u t i n d u ce d li mi t: g i v e n a ga i n o f 7.5 a nd ass u ming a maxim u m ou t p u t o f 2.9 v wi th a 3 v s u p p l y , th e maxim u m in p u t is (2.9 v r m s)/7.5 o r 390 mv r m s. filtering a n i m po r t a n t as pect o f rm s - d c c o n v e r s i o n i s th e n e ed f o r av e r a g i n g ( t h e f u n c t i o n i s ro ot - m e a n - s q u a re ). f o r co m p lex rf wa v e fo r m s, s u ch as t h os e t h a t o c c u r in cd m a , t h e f i l ter in g prov i d e d by t h e on - c h i p , l o w - p a ss f i lte r , a l t h ou g h s a t i s f a c tor y f o r cw sig n als a b o v e 100 mh z, is inadeq ua t e w h en the sig n al h a s m o d u la ti o n co m p o n en t s tha t e x t e n d d o wn i n t o t h e k i l o he r t z re g i o n . f o r t h i s re a s on , t h e f l t r pi n i s prov i d e d : a ca pa ci t o r a t ta ch ed be tw een th i s p i n a n d v p o s ca n e x t e n d th e a v era g i n g t i m e to v e r y lo w f r e q uen c ies. offset an o f fs et v o l t a g e can b e adde d to t h e o u t p u t ( w h e n usin g t h e mso p v e rsio n) t o al lo w t h e us e o f ad cs w h os e ra n g e do es n o t ex tend do w n to g r o u n d . h o w e ver , acc u r a c y a t t h e lo w e n d deg r ades b e c a u s e o f t h e i n h e r e n t er r o r in t h is adde d v o l t a g e . this r e q u ir es tha t t h e iref ( int e r n a l re f e re n c e ) p i n be tied t o vpos an d s r e f ( sup p ly re f e re n c e ) to g rou n d . i n t h e iref m o de , t h e in t e r c ep t is g e n e r a t e d b y a n i n t e r n al r e f e r e n c e ce l l and is a f i xed 350 mv , in dep e n d en t o f the s u p p l y v o l t a g e . t o ena b le this in t e r c ep t, iref s h o u ld be o p en-c ir c u i t e d , a nd s r ef sh o u l d b e g r o u n d ed . i n t h e sref m o de , t h e v o lt a g e i s p r o v ide d b y t h e s u p p ly . t o i m p l em en t th i s m o de , ti e ir ef t o v p o s a n d s r ef t o v p o s . the o f fs et is t h e n p r o p o r t i o n al to t h e s u p p ly v o lt a g e and is 400 mv f o r a 3 v s u p p l y an d 66 7 mv f o r a 5 v su p p l y .
ad8361 rev. c | page 12 of 24 appli c a t ions ba sic connections f i g u re 3 6 t h rou g h f i g u re 3 8 s h ow t h e b a s i c c o n n e c t i ons f o r t h e ad8361 s msop v e rsio n in i t s t h r e e o p era t in g m o des. i n al l m o des, th e de vice is p o w e r e d b y a sin g le s u p p ly o f betw een 2.7 v a nd 5.5 v . the vpos p i n is deco u p led usin g 100 pf a nd 0.01 f ca p a ci t ors. th e q u ie s c en t c u r r en t o f 1.1 ma i n o p era t in g m o de ca n be r e d u ce d t o 1 a b y p u l l in g th e pw dn pi n up to v p o s . a 75 ? ext e r n al s h un t r e sis t an c e co m b i n es w i t h t h e ac-co u ple d in p u t t o g i v e an o v eral l b r o a d b and in p u t i m p e da n c e n e a r 50 ?. n o t e tha t t h e co u p li n g ca pa ci t o r m u s t be p l aced bet w een t h e in p u t an d t h e s h un t i m p e dance . i n p u t im p e dan c e a nd i n p u t co u p lin g a r e di s c uss e d i n m o r e det a i l b e lo w . the i n p u t co u p l i n g c a p a ci t o r co m b i n es wi t h t h e in t e r n al i n p u t r e sis t a n c e (f igur e 37) t o p r o v ide a hig h -p as s cor n er f r e q uen c y gi v e n b y th e eq ua ti o n in c r c f = 2 1 db 3 w i th th e 100 pf ca p a ci t o r s h o w n in f i gu r e 36 th r o ug h f i gu r e 3 8 , t h e hig h -p as s co r n er f r e q uen c y is a b o u t 8 mh z. 1 2 3 4 8 7 6 5 ad8361 vpos iref rfin pwdn sref vrms fltr comm r1 75 ? 0.01 f c c 100pf cfltr 100pf +v s 2.7v ? 5.5v rfin v rms 01088-c-036 f i gure 36. bas i c connec t ions for g r ou nd referenc e mod e 1 2 3 4 8 7 6 5 ad8361 vpos iref rfin pwdn sref vrms fltr comm r1 75 ? 0.01 f c c 100pf cfltr 100pf +v s 2.7v ? 5.5v rfin v rms 01088-c-037 f i gure 37. bas i c connec t ions for inter n al reference mod e 1 2 3 4 8 7 6 5 ad8361 vpos iref rfin pwdn sref vrms fltr comm r1 75 ? 0.01 f c c 100pf cfltr 100pf +v s 2.7v ? 5.5v rfin v rms 01088-c-038 f i gure 38. bas i c connec t ions for su p p l y referenced mod e the o u t p u t v o l t a g e is n o minal l y 7.5 t i m e s t h e i n p u t r m s v o l t a g e ( a c o n v e r s i o n g a i n of 7 . 5 v / v r m s ) . t h re e mo d e s of op e r a t i o n a r e s et b y t h e sref a nd iref p i n s . i n addi t i on t o t h e g r o u nd r e fer e n c e m o de s h own i n f i gur e 36, w h er e t h e ou t p ut v o l t a g e s w i n g s f rom arou nd ne ar g rou n d to 4 . 9 v on a 5 . 0 v supply , t w o addi t i o n a l m o d e s a l lo w a n o f fset vol t a g e to b e adde d to t h e o u t p ut. i n t h e in t e r n al r e fer e n c e m o de (f igur e 3 7 ), t h e o u t p u t v o l t a g e s w i n g is shif t e d u p wa r d b y a n in t e r n a l r e fer e n c e v o l t a g e o f 350 mv . i n su p p l y r e f e r e n c e d m o de (f igur e 38), a n o f fs et volt age of v s /7. 5 is adde d t o t h e o u t p ut v o l t a g e. t a b l e 4 s u m m a riz e s th e co n n e cti o n s , o u t p u t tra n s f e r fun c ti o n , a n d minim u m ou t p u t v o l t a g e ( i .e ., zer o sig n al) fo r eac h m o de . out p ut swing f i gur e 39 s h o w s th e o u t p u t s w ing o f th e ad836 1 f o r a 5 v supply vo lt age f o r e a ch of t h e t h re e m o d e s . i t i s cl e a r f rom f i gur e 39 t h a t op era t i n g t h e de vice in e i t h er in t e r n al r e fer e n c e mo d e or supply re f e re nc e d mo d e re d u c e s t h e e f f e c t ive dy n a m i c r a nge a s t h e output he a d ro o m d e c r e a s e s . t h e re sp ons e f o r l o wer s u p p l y v o l t a g e s i s s i m i la r (in th e s u p p l y r e f e r e n c ed m o de , th e o f fs et is smal ler), b u t t h e d y namic ra n g e r e d u ces f u r t h e r as he a d ro om d e c r e a s e s . f i g u re 4 0 show s t h e re sp o n s e of t h e ad8361 t o a cw in p u t f o r va r i o u s s u p p l y v o l t a g es. input (v rms) 5.0 4.5 0.0 0 0.5 0.1 0.2 0.3 0.4 3.0 1.5 1.0 0.5 4.0 3.5 2.0 2.5 output ( v ) supply ref internal ref ground ref 0.6 0.7 0.8 01088-c-039 f i gure 39. o u tput s w ing fo r g r ou nd , in tern al , and sup p ly refe r e nc ed mode , vpos = 5 v ( m sop o n ly)
ad8361 rev. c | page 13 of 24 input (v rms) 5.5 1.5 0 0.5 0.1 0.2 0.3 0.4 4.0 3.0 2.5 2.0 5.0 4.5 3.5 output ( v ) 1.0 0.5 0.0 5.5v 5.0v 3.0v 2.7v 0.6 0.7 0.8 01088-c-040 f i gure 40. o u tput s w ing fo r su p p ly v o l t ages of 2.7 v , 3. 0 v , 5. 0 v an d 5. 5 v (m so p o n ly ) d y na m i c ra nge b e ca us e the ad8361 is a linea r -r es p o ndin g de vice wi th a n o mi n a l tra n s f er fun c ti o n o f 7.5 v / v rm s , th e d y n a m i c ra n g e in db is n o t cle a r f r o m plo t s s u ch as f i gur e 39. a s t h e i n p u t le ve l is i n cr eased i n co n s ta n t d b s t e p s , th e o u t p u t ste p si z e (p er d b ) also i n cr ease s . f i g u r e 41 s h o w s t h e r e la ti o n s h i p betw ee n t h e o u t p u t s t ep si ze (i . e ., mv/db) and i n p u t v o l t a g e fo r a no minal t r a n sfer f u n c tion o f 7.5 v/v r m s. ta ble 4. co nn e c t i ons a nd n o mi na l tra n s f er f u nct i on for ground, int e r n a l , a n d su ppl y re fere nce mo des reference m o d e i r e f s r e f ou tpu t intercept (no signal) output g r o u n d v p o s c o m m z e r o 7 . 5 v in internal open comm 0.350 v 7.5 v in + 0.350 v s u p p l y v p o s v p o s v s / 7 . 5 7 . 5 v in + v s /7.5 input (mv) 700 200 0 500 100 200 300 400 500 400 300 600 mv/db 100 0 600 700 800 01088-c-041 f i gure 41. ide a l i zed o u tput step s i ze a s a f u nc ti on of inp u t v o ltag e pl ot s of output vo lt age ve r s u s i n put vo lt age re s u lt i n a st r a i g h t l i ne. i t m a y s o m e t i me s b e more u s e f u l to pl ot t h e e r ror on a lo ga r i t h mic s c a l e, as sh o w n in f i gur e 42. th e de v i a t ion o f t h e plo t fo r t h e ide a l st ra ig h t li n e ch a r ac t e r i st ic is ca us e d b y o u t p u t cli p p i ng a t t h e hig h e n d an d b y sig n al o f fs ets a t t h e lo w e n d . i t s h o u ld h o we v e r b e n o te d t h a t of fs ets a t t h e lo w end can b e e i th e r pos i ti v e o r n e ga ti v e , so thi s p l o t co uld also tr e n d u p w a r d s a t t h e lo w en d . f i gur e 9, f i gur e 10, f i gur e 12, a nd f i gur e 13 show a 3 s i g m a d i st r i but i o n of t h e d e v i c e e r ror f o r a l a r g e p o pu l a t i on of d e v i c e s . input (v rms) 2.0 ?0.5 0.01 0.5 0.0 1.5 1.0 e rror (db) ?1.0 ?1.5 ?2.0 1.0 1.9ghz 2.5ghz 900mhz 100mhz 100mhz 0.02 ( ? 21dbm) 0.1 (?7dbm) 0.4 (+5dbm) 01088-c-042 f i gure 42. r e pres en tative u n it, e rror in db v s . input l e vel , v s = 2 . 7 v i t is als o a p p a r e n t in f i gur e 42 t h a t t h e er r o r p l o t t e n d s t o s h if t t o th e ri gh t wi t h in cr ea s i n g f r e q ue n c y . b e ca use th e in p u t i m p e da n c e decr ea se s w i t h f r eq ue n c y , th e v o l t a g e a c t u all y a p pl i e d to t h e i n put a l s o te nds to de c r e a s e ( a s s u mi ng a c o nst a n t s o ur ce im p e dance o v er f r e q uen c y). th e d y na mic ra n g e is alm o s t co n s ta n t o v e r fr eq ue n c y , b u t w i t h a s m al l d e cr ea se in co n v er sio n gain a t hig h f r eq uenc y . inp u t c o u p ling an d m a t c hi ng the in p u t im p e dan c e o f th e ad 8361 decr eas e s wi th in cr easing f r eq ue n c y i n bo th i t s r e s i s t i v e a n d ca pa ci ti v e co m p o n en t s (f igur e 17). th e r e sis t i v e co m p on en t va r i es f r o m 225 ? a t 100 mh z down t o a b o u t 95 ? a t 2.5 gh z. a n u m b er o f o p t i o n s exis t fo r in p u t ma t c hi n g . f o r o p era t io n a t m u l t i p le f r e q ue n c ies, a 75 ? sh un t t o g r o u nd , as s h own in f i gur e 43, p r o v ides t h e b e st o v eral l ma t c h. f o r us e a t a si n g le f r e q u e nc y , a re s i st ive or a re a c t i ve m a tc h c a n b e u s e d . by plo t t i n g t h e in pu t im p e dan c e on a smi t h c h a r t , t h e b e s t va l u e f o r a r e sis t i v e ma t c h can be calc u l a t e d . th e v s wr c a n be he ld be lo w 1.5 a t f r eq uen c ies u p t o 1 gh z, ev en as t h e in p u t im p e dan c e va r i es f r o m p a r t t o p a r t . (b o t h in p u t im p e dan c e and in p u t c a p a ci t a nce can va r y b y u p to 20% a r o u nd t h e i r n o min a l val u es.) a t v e r y hig h f r eq uen c ies (i .e ., 1.8 gh z to 2.5 gh z), a s h un t r e sis t o r is n o t s u f f i cien t to r e d u ce t h e v s wr b e lo w 1.5. w h er e v s wr i s cr i t ical, r e m o ve t h e s h u n t com p o n e n t an d in s e r t a n in d u c t o r in s e r i es wi th th e co u p lin g c a p a ci t o r as s h own in f i gur e 44. t a bl e 5 g i ve s re c o m m e n d e d s h u n t re s i stor v a lu e s f o r v a r i ou s f r e q uen c ies and s e r i es ind u c t o r va l u es fo r hig h f r e q uen c ies. the c o u p l i n g ca pa c i t o r , c c , ess e n t ia l l y ac ts as a n ac - s h o r t and pl a y s n o i n t e n t io na l p a r t in t h e ma t c h i n g.
ad8361 rev. c | page 14 of 24 ad8361 rfin rfin r sh 01088-c-043 c c f i gure 4 3 . input coupl i n g / ma tchi ng o p ti o n s , br oa dband resi st o r ma tch ad8361 rfin rfin l m 01088-c-044 c c f i gure 4 4 . input coupl i n g / ma tchi ng o p ti o n s , s e ri es induc t o r m a tch ad8361 rfin rfin 01088-c-045 c c c m l m f i gure 4 5 . input coupl i n g / ma tchi ng o p t i ons, n a r r owban d r e ac t i ve m a t c h ad8361 rfin rfin 01088-c-046 c c r series f i gure 4 6 . input coupl i n g / ma tchi ng o p ti o n s , a t t e n u a t i n g the input si gnal table 5. r e com m ende d co mpone n t values for resistive or induct i v e i npu t ma t c hi ng ( f i g ure 43 a n d f i g u re 44) freuency matching com p onent 100 mhz 63.4 ? shunt 800 mhz 75 ? shunt 900 mhz 75 ? shunt 1800 mhz 150 ? shunt or 4.7 nh series 1900 mhz 150 ? shunt or 4.7 nh series 2500 mhz 150 ? shunt or 2.7 nh series a l ter na t i vely , a r e ac t i ve ma tch c a n b e i m pl e m e n te d u s i n g a sh u n t in d u c t o r t o g r o u n d a n d a s e r i es c a p a ci t o r , as s h o w n in f i gu r e 45 . a m e t h o d fo r ha n d calcu l a t in g t h e a p p r o p r i a t e ma t c hin g co m p o n en t s i s show n on p a ge 1 2 o f t h e ad83 06 d a ta s h ee t . m a t c hin g in this ma nn er r e s u l t s in v e r y smal l val u es f o r c m , e s peci all y a t hi g h f r eq u e n c i e s . a s a r e s u l t , a s t ra y c a pa c i ta n c e a s sma l l as 1 pf can sig n if ican t l y d e g r ade t h e qua l i t y o f t h e m a tch. the ma i n ad van t a g e o f a r e ac t i v e ma t c h is t h e i n cr e a s e in se n s i t i v i t y tha t r e s u l t s f r o m th e in p u t v o l t a g e be in g ga in ed u p ( b y t h e s q u a re ro ot of t h e i m p e d a nc e r a t i o ) by t h e m a tc h i ng n e tw o r k. t a b l e 6 s h o w s t h e r e c o mmende d values fo r r e ac t i v e ma t c hing. ta ble 6. r e com m en de d va lues for a rea c t i ve input matching (figure 45) freuenc y (m ) c m (pf) l m (n) 100 16 180 800 2 15 900 2 12 1800 1.5 4.7 1900 1.5 4.7 2500 1.5 3.3 input coupling using a s e ri es resistor f i gur e 46 s h o w s a t e chniq u e fo r co u p lin g t h e i n p u t sig n al i n t o th e ad8361 tha t ma y be a p p l icab le w h er e t h e in p u t sig n al is m u ch l a rg er t h a n t h e in p u t ra n g e o f t h e ad836 1. a s e r i es r e sis t o r co m b ines wi t h t h e in p u t im p e dan c e o f th e ad8361 t o a t t e n u a t e t h e i n p u t sig n al. b e c a us e t h is s e r i es r e sis t o r fo r m s a d i v i d e r w i t h th e f r eq ue n c y d e pen d en t in p u t im pe d a n c e , t h e a p pa r e n t g a i n ch a n g e s gr ea tl y w i t h f r eq uen c y . h o w e v e r , th i s m e th od h a s th e a d v a n t a g e o f v e r y l i t t l e po w e r be i n g ta p p ed o f f in rf p o w e r t r an smissio n a p pli c a t ion s . i f t h e r e sist o r is la rge co m p a r ed t o th e tra n s m i s s i o n li n e s im p e d a n c e , th en th e v s w r o f th e s y s t em i s r e la t i v e l y un a f f e ct ed . frequency (mhz) 200 0 500 re s i s t ance ( ? ) 100 0 250 150 50 1000 1500 2000 2500 3000 3500 0.2 0.5 0.8 1.1 1.4 1.7 cap acitance (pf) 01088-c-047 f i g u re 47. input i m pedance v s . f r eque nc y , sup p ly 3 v , s o t - 23 selecting the filter capacit o r the ad8361 s in t e r n al 27 pf f i l t er ca p a c i t o r is co nnec t e d in p a r a l l el w i t h an i n te r n a l re s i st an ce tha t va r i es wi th sig n al leve l f r o m 2 k? f o r s m al l sig n als t o 500 ? f o r la rg e si g n als. th e r e s u l t in g lo w-p a s s co r n er f r e q u e n c y b etwe e n 3 mh z and 12 mh z p r o v i d es ade q u a te f i l t e r in g fo r al l f r e q uen c ies ab o v e 240 mh z (i . e ., 1 0 tim e s t h e f r eq uen c y a t t h e o u t p u t o f th e s q ua r e r , w h ich i s t w ice t h e i n p u t f r e q uen c y). h o w e v e r , sig n als wi t h hig h p e a k - t o-a v er a g e ra t i o s , s u ch as cd m a o r w - cd ma s i gn als , a n d lo w f r eq ue n c y co m p o n en t s r e q u i r e a d d i t i o n al f i l t er in g. td m a sig n als, s u c h as gs m, p d c, o r p h s, ha v e a peak -t o a v e r a g e ra ti o th a t i s c l ose t o th a t o f a s i n u so i d , a n d th e in t e r n a l f i l t er is ade q u a te .
ad8361 rev. c | page 15 of 24 the f i l t er c a p a c i tanc e o f t h e ad8361 c a n b e a u g m en te d b y co nne c t i ng a c a p a c i to r b e twe e n p i n 6 (fl t r) and vp os. t a b l e 7 s h ow s t h e e f f e c t of s e ve r a l c a p a c i tor v a lu e s f o r v a r i ou s co mm unica t io n s sta n da r d s wi t h h i g h pe ak-t o-a v e r a g e ra t i os alo n g wi th t h e r e sid u al ri p p le a t th e o u t p u t , in pe ak-t o-p e a k a n d r m s v o lts. n o t e t h a t l a rg e f i l ter c a p a c i to rs i n cr e a s e t h e ena b l e and p u ls e r e sp on s e t i mes, as dis c uss e d b e low . table 7. ef fect of wave form a n d cfilt o n r e sidual ac o u t p u t residua l a c w a v e f o r m c fil t v dc mv p-p mv rms is95 reverse link open 0.5 550 100 1.0 1000 180 2.0 2000 360 0.01 f 0.5 40 6 1.0 160 20 2.0 430 60 0.1 f 0.5 20 3 1.0 40 6 2.0 110 18 is95 8-channel 0.01 f 0.5 290 40 forward link 1.0 975 150 2.0 2600 430 0.1 f 0.5 50 7 1.0 190 30 2.0 670 95 w-cdma 15 0.01 f 0.5 225 35 channe l 1.0 940 135 2.0 2500 390 0.1 f 0.5 45 6 1.0 165 25 2.0 550 80 ope r ation at low freq ue nc ies al th o u g h the ad8361 is s p ecif ied f o r o p era t ion u p t o 2.5 gh z, t h er e is n o lo w e r limi t on t h e op era t i n g f r e q uen c y . i t is o n ly n e ces s a r y t o in c r eas e the in p u t co u p lin g c a p a ci t o r t o r e d u ce t h e co r n er f r e q uen c y o f t h e in p u t hi g h -p as s f i lt er (us e a n i n p u t r e sis t a n c e o f 225 ? f o r f r eq uencies be lo w 100 mh z). i t is als o n e ces s a r y t o i n cr ea se th e f i l t e r ca pa ci t o r so tha t th e s i gn al a t t h e output of t h e s q u a r i ng c i rc u i t i s f r e e of r i ppl e . t h e c o r n e r f r e q uen c y is s et b y t h e com b ina t io n o f t h e in ter nal r e sis t a n ce o f 2 k? a nd t h e ex t e r n al f i l t er ca p a ci t a n c e . powe r consumption, enab le a n d powe r -on the q u ies c en t c u r r en t co n s um p t io n o f th e ad8 361 va r i es wi t h t h e si ze o f t h e i n p u t sig n al f r om ab o u t 1 ma fo r n o sig n al u p t o 7 ma a t an in p u t lev e l o f 0.66 v r m s (9.4 db m, r e 50 ?). i f th e in p u t is dr i v en b e yo nd t h is p o i n t, t h e s u p p ly c u r r en t in cr e a s e s st e e ply (s e e f i g u r e 16). th er e is li t t le va r i a t ion i n q u ies c e n t c u r r en t wi t h p o w e r s u p p ly v o l t a g e . the ad8361 can b e dis a b l ed ei th er b y p u l l in g t h e p w dn (p in 4) t o vpos o r b y sim p l y t u r n in g o f f th e p o w e r t o th e de vice . w h i l e t u r n in g o f f t h e de vice ob vio u s l y elimina t es t h e c u r r en t co n s um p t io n, dis a b l in g t h e de vice r e d u ces t h e le a k a g e c u r r en t t o les s tha n 1 a. f i gure 27 a nd f i gur e 28 s h o w t h e r e s p o n s e o f t h e o u t p u t o f th e ad8361 t o a p u ls e o n t h e p w d n p i n, wi t h n o ca p a ci tan c e an d wi t h a f i l t er ca p a c i t a n c e o f 0.01 f , r e s p ecti v e l y ; th e t u rn - o n tim e i s a fun c ti o n o f th e f i l t e r c a p a c i tor . f i g u re 3 1 show s a pl ot of t h e output r e sp ons e to t h e s u p p l y bein g t u r n ed o n (i .e ., pw d n is g r o u n d ed and vpos is p u lsed ) wi th a f i l t e r ca pa ci t o r o f 0. 01 f . a g a i n , th e t u rn - o n time is s t r o n g l y inf l uen c e d b y t h e size o f t h e f i l t er ca p a c i t o r . i f th e in p u t o f t h e ad8361 is dr i v en while t h e de vice is dis a b l e d (pwd n = vp o s ), t h e le aka g e c u r r en t o f les s t h a n 1 a i n cr ease s a s a fun c ti o n o f i n p u t lev e l . w h en t h e d e v i ce i s d i sa b l e d , th e o u t p u t i m pe d a n c e i n cr ea ses t o a p p r o x i m a t e l y 16 k?. volts to d b m conv ersion i n man y o f the p l o t s, th e h o r i zo n t al axis is s c ale d in bo t h r m s vol t s an d dbm. i n a l l c a s e s, dbm a r e ca lc u l a t e d r e l a t i ve to a n im p e dan c e o f 5 0 ?. t o co n v er t b e tw e e n dbm and v o l t s i n a 50 ? s y s t e m , th e f o llo w i n g eq ua ti o n s ca n b e used . f i g u r e 48 s h o w s t h is con v ersio n in g r a p hical fo r m . () () () () 2 2 20 10log w 0.001 50 10log dbm rms v rms v power = ? ? ? ? ? ? ? ? ? ? ? ? ? ? = () 20 /10 log 10 log 50 w 0.001 1 1 dbm dbm rms v ? ? = ? ? ? ? ? ? = v rms dbm +20 +10 0 ?10 ?20 ?30 ?4 0 1 0.1 0.01 0.001 01088-c-048 f i gur e 4 8 . c o n v er sio n fr om dbm to r m s v o l t s
ad8361 rev. c | page 16 of 24 out p ut dri v e capability and b u ffering the ad8361 is ca p a b l e o f s o ur c i n g a n ou t p u t c u r r en t o f a p p r o x ima t e l y 3 ma. i f add i t i o n a l c u r r en t is r e q u ir e d , a si m p le b u f f er in g cir c ui t can b e us ed as s h o w n in f i gur e 51. s i mila r cir c ui ts can be us ed t o in cr ea se o r d e cr ea se th e n o mi n a l co n v ersio n gain o f 7.5 v/v r m s (f igur e 49 a nd f i gur e 50). i n f i gur e 50, th e ad8031 b u f f ers a r e sis t i v e divider t o g i v e a s l o p e o f 3.75 v/v r m s. i n f i gur e 49, th e o p am p s ga in o f tw o in cr eas e s t h e sl op e to 1 5 v / v r m s . u s i n g ot he r re s i stor v a lu e s , t h e sl op e ca n be c h a n g e d t o a n a r b i t ra r y val u e . t h e ad8031 ra il-t o-ra il o p a m p , us ed in th es e exam p l e , ca n s w in g f r o m 50 mv t o 4.95 v o n a sin g le 5 v su p p l y a nd o p er a t e a t s u p p l y v o l t a g es do wn t o 2.7 v . i f hig h o u t p u t c u r r en t is req u ir ed (>10 ma), th e ad8051, whic h als o has ra il-t o- ra i l c a p a b i li ty , can be us ed do wn t o a s u p p l y v o l t a g e o f 3 v . i t ca n de liv e r u p t o 45 ma o f o u t p u t c u r r en t. 100pf 0.01 f 0.01 f ad8361 vout vpos comm pwdn 5k ? 5k ? 5v 15v/v rms ad8031 01088-c-049 f i g u re 49. o u t p ut b u f f e ring o p t i ons, s l ope of 1 5 v / v r m s 100pf 0.01 f 0.01 f ad8361 vout vpos comm pwdn 5v 3.75v/v rms ad8031 5k ? 5k ? 10k ? 01088-c-050 f i g u re 50. o u t p ut b u f f e ring o p t i ons, s l ope of 3 . 7 5 v / v r m s 100pf 0.01 f 0.01 f ad8361 vout vpos comm pwdn 5v 7.5v/v rms ad8031 01088-c-051 f i g u re 51. o u t p ut b u f f e ring o p t i ons, s l ope of 7 . 5 v / v r m s output re ference te mper a t ure drift c o mpensa tion the er r o r d u e to lo w t e m p era t ur e dr if t o f th e ad8361 can be r e d u ce d if t h e tem p e r a t u r e is k n o w n. m a n y syst em s i n co r p o r a te a t e m p era t ur e s e n s o r ; t h e o u t p u t o f t h e s e n s o r is typ i cal l y d i gi t i zed , fa cili t a ti n g a so f t w a r e co rr ecti o n . u s in g th i s info r m a t io n, o n ly a tw o-p o in t c a li b r a t ion a t am b i e n t is r e q u ir e d . the o u t p u t v o l t a g e o f t h e ad83 61 a t am b i e n t (2 5c) can b e exp r es s e d b y t h e e q u a t i on ( ) ? ? + = w h er e gain is t h e con v ersion ga in i n v/ v r m s a nd v os is t h e ext r a p ola t e d o u t p u t v o lt a g e fo r a n i n p u t l e v e l o f 0 v . gain an d v os ( a l s o ref e r r e d to a s i n te rc e p t an d output re f e re nc e ) c a n b e calc u l a t e d a t am b i e n t usin g a si m p le tw o - p o i n t calib r a t ion b y m e as ur in g t h e ou t p ut v o l t a g es fo r tw o s p e c if ic i n p u t l e v e ls. c a li b r a t io n a t ro ug hl y 35 mv r m s (?16 db m) and 250 mv r m s ( + 1 dbm) is r e co mmende d fo r max i m u m li n e ar d y na mic r a n g e. h o w e v e r , al t e r n a t i v e l e v e ls and ra n g es can b e ch os en t o s u i t t h e ap p l i c at i o n . gain an d v os a r e th e n c a l c ula t ed u s i n g t h e eq ua ti o n s ( ) ? ? = ( ) ? = bo t h gain and v os dr if t o v er t e m p er a t ur e . h o w e v e r , t h e dr if t of v os has a b i g g er inf l uen c e on t h e er r o r r e la t i v e t o t h e o u t p ut. this can be s een b y in s e r t in g da ta f r o m f i gur e 18 a nd f i gur e 2 1 (in t er cept dr if t a nd con v ersio n ga in) in t o t h e e q ua t i o n fo r v ou t . t h e s e pl ot s are c o ns i s te n t w i t h f i g u re 1 4 an d fi g u re 1 5 , w h i c h s h o w t h a t t h e er r o r d u e t o t e m p era t ur e dr if t de c r e a s e s w i t h i n c r e a s i ng i n put l e vel. t h i s re su lt s f rom t h e of f s e t e r ror h a v i ng a dimi nis h i n g inf l uen c e w i t h i n cre a sin g le ve l o n t h e o v eral l m e as ur e m en t er r o r . f r o m f i gur e 18, t h e a v era g e in t e r c ep t dr if t is 0.4 3 mv/ c f r o m ?40c t o +25c a nd 0.17 mv/c f r o m +25c to +85c. f o r a l e ss r i gorou s c o m p e n s a t i o n s c h e me, t h e a v e r ag e d r i f t ove r t h e co m p let e t e m p era t ur e ra n g e can b e calc u l a t e d as () () () c / v 0.000304 c 40 c 85 v 0.028 v 0.010 c / v = ? ? ? ? ? ? ? ? ? ? + ? ? = w i th th e d r i f t o f v os i n c l u d e d , th e eq ua t i o n f o r v ou t beco m e s v ou t = ( gain v in ) + v os + dr i f t vo s (te m p ? 25 c )
ad8361 rev. c | page 17 of 24 the e q ua t i on c a n b e r e wr i t t e n to yie l d a tem p e r a t u r e co m p en s a t e d va l u e f o r v in : () ( ) gai n temp drift v v v vos os out in c 25 ? ? ? = f i g u re 5 2 show s t h e output vo lt age a n d e r ror ( i n d b ) a s a f u n c t i on o f in pu t le v e l fo r a typical de v i ce ( n o te t h a t o u t p ut v o l t a g e is plo t t e d o n a loga r i t h mic s c ale). f i gu r e 53 s h o w s t h e er r o r in t h e calc u l a t e d i n p u t le ve l a f t e r t h e t e m p era t ur e co m p en sa t i o n alg o ri th m h a s be e n a p p l i e d . f o r a s u p p l y v o l t a g e o f 5 v , t h e p a r t exhi b i ts a w o rs t- cas e li n e a r i t y er r o r o v er t e m p era t ur e o f a p p r o x ima t e l y 0.3 db o v er a d y na mic ran g e o f 35 db . pin (dbm) 2.5 ?25 0 ? 2 0 ? 15 ?10 ? 5 1.0 2.0 1.5 0.5 e rror (db) 51 0 +25c ?40 c 0 ?0.5 ?1.0 ?1.5 ?2.0 ?2.5 0.1 10 1.0 v out (v ) +85 c 01088-c-052 f i gure 52. t y pic a l o u tput v o ltage an d e rror v s . input l e vel , 8 00 m h z, v p os = 5 v pin (dbm) ?25 0 ?2 0 ? 1 5 ?1 0 ? 5 1.0 2.0 1.5 0.5 e rror (db) 51 0 0 ? 0.5 ? 1.0 ? 1.5 ? 2.0 ? 2.5 +25 c ?4 0 c +85c ? 3.0 ?30 01088-c-053 f i gure 53. e rror a f ter t e mper ature co mpens a ti on of o u tput refer e nce , 8 00 m h z, v pos = 5 v extended frequen c y ch aracteriz a tion al th o u g h the ad8361 was o r ig inal l y in t e nded as a p o w e r m e as ur em en t and co n t r o l de vice f o r ce l l u l a r wir e les s a p p l ic a t ion s , th e ad8361 has us ef u l p e r f o r ma n c e a t hig h er f r eq uen c ies. t y p i cal a p p l ic a t ion s ma y in c l ude mmds, lmds, w l a n , a n d ot h e r no nc el lu l a r a c t i v i t i e s . i n o r d er t o c h a r ac t e r i ze t h e ad8361 a t f r eq uencies g r ea t e r than 2 . 5 g h z , a s m a l l c o l l e c t i on of d e v i c e s we re te st e d . d y n a m i c r a nge, c o n v e r s i on g a i n , a n d output i n te rc e p t we r e me a s u r e d a t s e v e ral f r e q ue ncies o v er a t e m p era t ur e ra n g e o f ?30c t o +80c. b o th cw a n d 64 q a m m o d u la t e d in p u t wa v e f o rm s w e r e used in t h e cha r ac ter iza t io n p r o c es s i n o r d er t o access va r y in g p e a k - to - a ve r a ge w a ve for m p e r f o r manc e . the d y na mic ran g e o f t h e de vic e is calc u l a t e d as t h e i n p u t p o w e r ra n g e o v er w h ich t h e de vice r e main s w i t h in a p e r m is si b l e er ro r ma rg in t o t h e ide a l t r a n sfer f u n c t i on. d e vice s we re te ste d ove r f r e q u e nc y and te m p e r a t u r e. a f te r i d e n t i f y i n g a n accep t a b le er r o r ma r g in f o r a g i v e n a p p l ic a t io n, th e us ab le d y n a m i c m e a s ur e m en t ra n g e ca n b e i d en ti f i e d us i n g th e p l o t s in f i g u re 5 4 t h rou g h f i g u re 5 7 . f o r i n st a n c e , f o r a 1 d b e r ror ma rg in an d a mo d u l a te d c a r r i er a t 3 g h z, t h e us a b le d y n a mic r a nge c a n b e fou n d b y insp e c t i ng t h e 3 g h z pl o t o f f i gure 5 7 . n o t e t h a t t h e ? 30c c u r v e cr os s e s t h e ?1 db er r o r limi t a t ? 17 dbm. f o r a 5 v su p p ly , t h e max i m u m in p u t p o wer sh o u ld n o t exce e d 6 dbm in o r d e r to a v o i d co m p r e ssion. t h e r e su l t an t us a b le d y namic ra n g e is t h er efor e 6 db m ? (?17 db m) o r 23 db m o v er a t e m p era t ur e r a n g e o f ?30c to +80c. pin (dbm) 2.5 ?25 e rror (db) 2.0 1.5 1.0 0.5 0 ?0.5 ?1.0 ?1.5 ?2.0 ?2.5 ?20 ? 15 ?10 ? 5 0 5 1 0 10 1 0.1 v out (v ) +80c +25 c ?30 c 01088-0-054 f i g u re 54. t r ans f er f u nc t i on and e r ror p l ot s m e as ured at 1 . 5 ghz fo r a 64 q a m mo dula te d si gna l
ad8361 rev. c | page 18 of 24 pin (dbm) 2.5 ?2 5 e r ror (db) 2.0 1.5 1.0 0.5 0 ?0.5 ?1.0 ?1.5 ?2.0 ?2.5 ? 2 0 ? 15 ?10 ? 5 0 5 1 0 10 1 0.1 v out (v ) +80 c +25 c ?3 0 c 01088-c-055 f i g u re 55. t r ans f er f u nc t i on and e r ror p l ot s m e as ured at 2 . 5 ghz fo r a 64 q a m mo dula te d si gna l pin (dbm) 2.5 ?25 e rror (db) 2.0 1.5 1.0 0.5 0 ?0.5 ?1.0 ?1.5 ?2.0 ?2.5 ?20 ? 15 ?10 ? 5 0 5 1 0 10 1 0.1 v out (v ) +80 c +25 c ?3 0 c 01088-c-056 f i g u re 56. t r ans f er f u nc t i on and e r ror p l ot s m e as ured at 2 . 7 ghz fo r a 64 q a m mo dula te d si gna l pin (dbm) 2.5 ?2 5 e rror (db) 2.0 1.5 1.0 0.5 0 ?0.5 ?1.0 ?1.5 ?2.0 ?2.5 ?2 0 ? 1 5 ? 1 0 ? 5 5 01 0 10 1 0.1 v out (v ) +80 c +25 c ?30 c 01088-c-057 f i g u re 57. t r ans f er f u nc t i on and e r ror p l ot s m e as ured at 3 . 0 ghz fo r a 64 q a m mo dula te d si gna l pin (dbm) 2.5 ?2 5 e r ror (db) 2.0 1.5 1.0 0.5 0 ?0.5 ?1.0 ?1.5 ?2.0 ?2.5 ?2 0 ? 1 5 ? 1 0 ? 5 5 01 0 10 1 0.1 v out (v ) cw 64 qam 01088-c-058 f i gure 58. e rror f r o m c w lin e a r r e fe renc e v s . input d r ive l e vel fo r c w and 64 qa m m o du lat e d s i g n a l s at 3. 0 gh z frequency (mhz) 8.0 100 conversion gain ( v /v rms) 7.5 7.0 6.5 6.0 5.5 5.0 200 400 800 1200 1600 2200 2500 2700 3000 01088-c-059 fi g u r e 5 9 . c o n v e r s i o n g a i n v s . fr e q u e n c y f o r a t y pic a l d e v i ce , sup p ly 3 v , ground r e f e r e nc e m o de the t r a n sfer f u n c t i o n s an d er r o r fo r a cw in pu t an d a 64 q a m in p u t wa vefo r m is s h o w n i n f i g u r e 58. th e er r o r c u r v e is ge ne r a te d f rom a l i ne ar re f e re nc e b a s e d on t h e c w d a t a . t h e i n c r e a s e d c r e s t f a c t or of t h e 6 4 q a m mo d u l a t i on re su lt s i n a decr eas e in o u t p u t f r o m the ad8361. this dec r eas e in ou t p u t is a r e su l t o f t h e li mi te d b a ndwi d t h an d com p r e ss io n o f t h e in t e r n a l ga i n st ages. this inacc u rac y sh o u ld b e acco un te d fo r i n sys t em s w h er e v a r y in g cr es t fac t o r sig n als n e e d t o b e m e as ur e d . the con v ersio n ga in is def i n e d as t h e s l o p e o f t h e o u t p ut v o l t a g e v e r s us th e in p u t rm s v o l t a g e . a n i d eal bes t f i t cur v e ca n be f o un d f o r th e m e a s ur ed tra n s f e r fun c ti o n a t a gi v e n s u p p l y v o l t a g e and t e m p era t ur e . th e s l o p e o f t h e i d e a l c u r v e is iden t i f i e d as t h e co n v ersio n gai n fo r a p a r t ic u l a r de v i ce . th e co n v ersio n gain r e la t e s t h e m e as ur em e n t s e n s i t i v i t y o f t h e ad8361 t o t h e r m s in p u t v o l t ag e o f th e rf wa v e f o r m . th e co n v ersio n gain was m e as ur e d fo r a n u m b er o f de vices o v er a t e m p era t ur e ra ng e o f ?30c t o +80c. the con v ersio n ga in fo r a typ i cal de vic e is s h o w n i n f i gure 59. a l t h o u g h t h e con v ersion ga in t e n d s t o de cr eas e wi th in cr easin g f r eq uen c y , th e ad8361 p r o v ides me as u r em e n t c a p a b i li ty a t f r e q ue n c ie s g r e a t e r t h a n
ad8361 rev. c | page 19 of 24 on e o f t h e ad8 361s (u2) has a n et gain o f abo u t 14 db p r e c e d i n g i t and t h er efo r e o p er a t es m o s t acc u r a t e l y a t lo w in pu t sig n al lev e ls. this is r e f e r r ed t o as the w e ak sig n al p a th. u4, o n t h e o t h e r hand , do es n o t ha ve t h e a dde d ga i n and p r o v ides a c c u r a te re sp o n s e a t h i g h l e vel s . t h e output of u 2 i s atte n u a t e d b y r1 in o r d er to ca n c e l t h e ef f e c t o f u2 s p r ece d in g ga in s o tha t th e s l o p e o f th e tra n s f e r fun c ti o n (a s seen a t t h e s l i d e r o f r 1 ) i s th e s a me as tha t o f u4 b y i t s e lf . 2.5 gh z. h o we v e r , i t is n e cess ar y to ca li b r a t e fo r a g i v e n a p plic a t ion t o a cco mm o d a t e for t h e cha n ge in co n v ersio n gain at h i g h e r f r e q u e n c i e s . dynamic range extension for the ad836 1 the acc u ra t e me as ur emen t rang e o f t h e ad83 61 is limi te d b y i n t e rn al d c o f fsets f o r sm all i n p u t si gn als a n d b y sq ua r e la w co nfo r ma n c e er r o r s fo r la rg e si g n als. th e m e asur em en t ra n g e ma y b e ext e n d e d b y usin g tw o de vices o p era t i n g a t dif f er en t s i gn al lev e ls a n d th en ch oos i n g o n l y th e o u t p u t o f th e dev i ce th a t p r o v i d e s a ccura t e r e s u l t s a t th e p r ev a i lin g in p u t lev e l . the cir c ui t com p r i sin g u3, u5, a nd u6 is a cr ossfader , in w h ich t h e r e la t i v e ga i n s o f t h e tw o i n pu ts a r e deter mi n e d b y t h e o u t p u t c u r r e n t s of a f u z z y c o m p ar a t or m a d e f rom q 1 an d q 2 . a s s u min g tha t t h e s l ider o f r2 is a t 2.5 v dc, t h e f u zzy co m p a r a t o r co mman d s f u l l w e ig h t in g o f th e weak sig n al p a t h w h e n t h e output of u 2 i s b e l o w ab out 2 . 0 v d c , an d f u l l we i g h t i n g of t h e st rong s i g n a l p a t h w h e n t h e o u tput of u 3 exce e d s a b o u t 3 . 0 v dc. u3 an d u5 a r e ot a s (op e ra t i o n al t r ans c ond u c t a n c e am pl i f i e rs ) . f i g u r e 60 d e p i cts a n im p l em e n t a ti o n o f th i s i d e a . i n th i s ci r c ui t , t h e s e le c t io n o f t h e o u t p ut is made g r ad ual l y o v er a n in p u t l e ve l r a n g e o f a b o u t 3 db in o r der to minim i ze t h e i m p a c t o f i m pe rf ect ma t c h i n g o f th e tra n s f e r fun c ti o n s o f th e t w o ad8361s. s u c h a misma t c h typ i cal l y a r is es bec a us e o f th e v a ri a t i o n o f th e g a i n o f th e r f p r ea m p li f i e r u 1 a n d bo th t h e ga in and s l o p e va r i a t ion s o f th e ad8361s wi t h tem p e r a t u r e . 8 7 6 5 1 2 3 4 ad8361 0.1 f 5v 100pf 5v 0.01 f 68 ? u2 era-3 20db u1 rfc 270 ? 12v 6db pa d 6db splitter rf input 12v 20k ? 1k ? 1k ? 5v r2 10k ? q2 2n3906 q1 2n3906 16k ? r1 5k ? ca3080 +12v ?5 v u3 20k ? ca3080 +12v ?5 v u5 2 3 5 6 2 3 5 6 20k ? 1m ? r3 10k ? ?5v +5v 12k ? 8 7 6 5 1 2 3 4 ad8361 0.1 f 5v 100pf 5v 0.01 f 68 ? u4 ad820 5v u6 2 3 8.2nf 4 7 6 v out 100 ? 01088-c-060 f i g u re 60. ra ng e e x tende r a p plic ation
ad8361 rev. c | page 20 of 24 u6 p r o v ides fe e d b a ck t o li n e a r i z e t h e i n h e r e n t t a nh t r an sfer f u nc t i o n of t h e ot a s . whe n o n e o t a or t h e ot he r i s f u l l y s e le c t e d , t h e fe e d b a ck is v e r y ef f e c t i v e . th e ac t i ve ot a has zer o dif f er en t i al in put; t h e inac t i v e on e has a p o t e n t i a l l y la rg e dif f er en t i al in put, b u t t h is do es n o t ma t t er b e c a us e t h e inac t i v e o t a is n o t con t r i b u t i n g t o t h e o u t p ut. h o w e v e r , w h en b o t h o t a s a r e ac t i v e t o s o me ext e n t , a nd t h e t w o sig n al in pu ts t o t h e cr os sfader a r e dif f er en t, i t is i m p o s s i b le t o ha v e zer o dif f er en t i a l in p u ts o n t h e ot a s . i n t h is e v e n t, t h e cr os sfade r admi t t e d ly g e n e ra t e s d i s t o r ti o n beca use o f th e n o nlin ea r tra n s f e r fun c ti o n o f th e o t a s . f o r t un a t e l y , i n th i s a p p l i c a t i o n , th e d i s t o r ti o n i s n o t v e r y ob j e c t i o na b l e fo r tw o r e as o n s: 1. the misma t ch i n in p u t le v e ls t o t h e cr os sfader i s ne v e r la rg e en o u g h t o e v ok e v e r y m u ch dist o r t i o n b e c a us e t h e ad8361s a r e r e as o n a b l y w e l l - b e ha v e d . 2. t h e e f f e c t of t h e d i stor t i on i n t h i s c a s e i s m e rel y to d i stor t t h e o t h e r w is e ne a r ly lin e a r s l o p e o f t h e t r a n s i t i o n b etwe e n t h e cr os sfader s tw o in p u ts. v out m 1 m 2 m 1 m 2 differing slopes indicate maladjustment of r1 rf input level ? v rms transition region 01088-c - 061 f i g u re 61. sl ope adjus t ment this cir c ui t has t h r e e t r imma b l e p o t e n t iom eters. th e s u g g es te d se t u p p r oced ur e i s a s f o llo w s : 1. p r es et r3 a t mi dra n g e . 2. s et r2 s o t h a t i t s s l ider s v o l t a g e is a t t h e mi ddle o f t h e desir e d t r a n si t i o n zone ( a b o ut 2.5 v dc is r e co mmende d) . 3. s et r1 s o t h a t t h e t r an sfer f u n c t i o n s s l o p es a r e e q ual on bo th s i d e s o f th e tra n s i ti o n z o n e . t h i s i s pe r h a p s be s t a c c o m p l i s h e d by m a k i ng a pl ot of t h e ove r a l l t r ans f e r f u nc t i o n ( u s i ng l i ne ar vo lt age s c a l e s for b o t h a x e s ) to a s s e ss t h e ma t c h i n s l op e b etwe e n one side o f t h e t r a n s i t i o n re g i on a n d t h e ot he r ( s e e f i g u r e 6 1 ) . n o te : it m a y b e h e l p f u l t o ad j u st r3 t o r e m o v e an y la r g e mis a l i g n m e n t in t h e t r a n sfer f u nc t i o n i n o r d er to co r r e c t l y p e r c ei v e s l o p e dif f er en ces. 4. f i nal l y (r e)ad j u s t r3 as r e q u ir e d t o r e m o v e an y r e ma inin g m i sali gnm e n t in th e tra n s f e r fun c ti o n (see f i g u r e 62). v out rf input level ? v rms transition region misalignment indicates maladjustment of r3 01088-c - 062 f i g u re 62. inte r cept adjus t ment i n p r in ci p l e , this m e t h o d co u l d be ext e n d ed t o thr e e o r m o r e ad8361s in p u rs ui t o f ev en m o r e m e as ur emen t ra n g e . h o w e v e r , i t is v e r y im p o r t a n t t o p a y clos e a t t e n t io n t o t h e ma t t er o f n o t exces s i v e l y o v er dr i v in g the ad8361s in t h e w e ak er sig n al p a ths un der st r o n g si g n a l co ndi t i on s. f i gur e 63 s h o w s t h e ext e n d e d ran g e t r a n sfer f u nc t i o n a t m u l t i p l e te m p e r a t u r es . the di s c on t i n u i t y a t a ppro x i m a tely 0 . 2 v r m s a r i s es as a r e s u l t o f co m p o n en t t e m p era t ur e dep e n d en cies. f i gur e 64 s h o w s t h e err o r i n db o f t h e ra n g e ext e n d er cir c ui t a t a m b i en t t e m p era t ur e . f o r a 1 db e r r o r ma r g in, t h e ra n g e e x t e n d er ci r c ui t o f fe rs 38 db o f m e as ur em en t ra n g e . drive level (v rms) 3.0 2.5 0 0 1.0 0.2 v ou t (v ) 0.4 0.6 0.8 2.0 1.5 1.0 0.5 ref line +80 c ?30 c 01088-c - 063 f i gure 63. o u tput v s . d r ive l e vel o v e r t e mper atur e for a 1 g h z 64 qa m m o dul a ted sig n a l drive level (dbm) 5 ?32 e rror (db) 4 3 2 1 0 ?1 ?2 ?3 ?4 ?5 ?27 ? 22 ? 1 7 ? 12 ?7 ?2 3 8 13 01088-c - 064 f i gure 6 4 . e r r o r fro m li ne ar r e f e renc e at 2 5 c for a 1 gh z 64 qa m m o dulat e d s i g n a l
ad8361 rev. c | page 21 of 24 evaluation board figure 65 and figure 68 show the schematic of the ad8361 evaluation board. note that uninstalled components are drawn in as dashed. the layout and silkscreen of the component side are shown in figure 66, figure 67, figure 69, and figure 70. the board is powered by a single supply in the 2.7 v to 5.5 v range. the power supply is decoupled by 100 pf and 0.01 f capacitors. additional decoupling, in the form of a series resistor or inductor in r6, can also be added. table 8 details the various configuration options of the evaluation board. table 8. evaluation board configuration options component function default condition tp1, tp2 ground and supply vector pins. not applicable sw1 device enable. when in position a, the pwdn pin is connected to +v s and the ad8361 is in power- down mode. in position b, the pwdn pin is gr ounded, putting the device in operating mode. sw1 = b sw2/sw3 operating mode. selects either ground refere nce mode, internal reference mode or supply reference mode. see table 4 for more details. sw2 = a, sw3 = b (ground reference mode) c1, r2 input coupling. the 75 ? resistor in position r2 combines with the ad8361s internal input impedance to give a broadband input impedance of around 50 ?. for more precise matching at a particular frequency, r2 can be replaced by a different value (see input coupling and matching and figure 43 through figure 46). capacitor c1 ac couples the input signal and creates a high-pass input filter whose corner frequency is equal to approximately 8 mhz. c1 can be increased for operation at lower frequencies. if resistive attenuation is desired at the input, series resistor r1, which is nominally 0 ?, can be replaced by an appropriate value. r2 = 75 ? (size 0402) c1 = 100 pf (size 0402) c2, c3, r6 power supply decoupling. the nominal supply decoupling of 0.01 f and 100 pf. a series inductor or small resistor can be placed in r6 for additional decoupling. c2 = 0.01 f (size 0402) c3 = 100 pf (size 0402) r6 = 0 ? (size 0402) c5 filter capacitor. the internal 50 pf averaging capacitor can be augmented by placing a capacitance in c5. c5 = 1 nf (size 0603) c4, r5 output loading. resistors and capaci tors can be placed in c4 and r5 to load test v rms. c4 = r5 = open (size 0603)
ad8361 rev. c | page 22 of 24 1 2 3 4 8 7 6 5 ad8361 vpos iref rfin pwdn sref vrms fltr comm c2 0.01 f c3 100pf c1 100pf c5 rfin v rms vpos v s sw2 v s sw3 sw1 a b a b 1nf a b tp2 tp1 vpos vpos r2 75 ? r4 0 ? r6 0 ? c4 (open) r5 (open) 01088- c - 065 f i g u re 65. ev aluat i on b o a r d s c h e m a t i c , m s op 01088-c-066 f i g u re 66. layo ut o f compon ent sid e , m s op 01088-c-067 f i gure 67. si lks c ree n of compon ent s i de , mso p r2 75 ? r7 50 ? r4 0 ? c2 0.01 f c1 100pf c3 100pf c5 1nf j2 j3 j1 tp2 c4 (open) r5 (open) ad8361 vpos rfin pwdn vrms fltr comm tp1 sw1 1 2 3 vpos 1 2 3 6 5 4 01088- c- 068 f i g u re 68. ev aluat i on b o a r d s c h e m a t i c , so t - 2 3 01088-c-069 f i gure 69. layo ut o f the co mponent si de , s o t - 2 3 01088-c-070 f i gure 70. silkscree n of the c o mponen t side , so t - 23
ad8361 rev. c | page 23 of 24 pr ob lem s c a us e d b y im p e dan c e misma t ch ma y a r is e usin g t h e eval ua tion bo a r d t o exa m in e t h e ad8361 p e r f o r ma n c e . on e wa y t o r e d u ce t h es e p r ob lem s i s t o p u t a co axi a l 3 db a t t e n u a t or o n the rfin s m a co nn ec t o r . m i sma t ch es a t t h e s o ur ce , ca b l e , an d c a bl e i n te rc on ne c t i o n , a s w e l l a s t h o s e o c c u r r i ng on t h e ev al ua ti o n boa r d , ca n ca use th ese p r o b le m s . a sim p le (and c o mm on) exa m ple o f s u c h a p r ob lem is tr i p le t r a v e l d u e t o m i s m a t c h a t b o th th e s o u r c e a n d th e e v a l u a ti o n b o ard. h e re t h e s i g n a l f rom t h e s o u r c e re a c he s t h e e v a l u a t i on boa r d a n d m i sm a t ch ca use s a r e f l ecti o n . w h en th a t r e f l ecti o n re a c he s t h e s o u r c e m i s m atch , it c a u s e s a n e w re f l e c t i on , w h i c h tra v e l s ba ck t o th e ev al ua t i o n b o a r d , a d d i n g t o th e o r i g i n al sig n al in c i de n t a t t h e b o a r d . the r e s u l t a n t v o l t ag e va r i es w i t h bo th ca b l e le n g t h a n d f r eq uen c y d e pe n d e n c e o n th e r e la ti v e phas e o f t h e in i t ia l and r e f l e c te d sig n a l s. placin g t h e 3 db p a d a t t h e i n p u t o f t h e b o a r d i m p r o v es t h e ma t c h a t t h e b o a r d and t h u s r e d u ces the s e nsi t ivi t y t o misma t ch es a t t h e s o ur ce . w h en s u ch p r eca u t i o n s a r e tak e n , m e a s ur em en t s a r e le s s s e n s i t i v e t o ca b l e len g t h an d o t h e r f i xt ur e issues. i n an ac tua l a p plica t ion w h e n th e dis t an c e b e tw een ad8361 and s o ur ce is sh or t a n d we l l d e f i ne d, t h i s 3 d b a tte n u a t or i s not ne e d e d . char a c teriz a ti on se t u ps equip m e n t t h e pr i m ar y ch ar a c te r i z a t i on s e tup i s s h ow n i n f i g u re 7 2 . t h e sig n al s o ur ce us ed was a rohde & s c h w a r z s m i q 03b , v e rsio n 3.90hx. th e mo d u l a t e d wa v e fo r m s us ed f o r is95 r e v e rs e lin k , is95 nine ac ti ve c h a n n e ls f o r w a r d (f o r wa r d link 18 s e t t in g), a nd w - cd m a 4-cha n n e l an d 1 5 -cha n n el w e r e gen e r a te d usin g t h e def a u l t s e tt i n gs co ding an d f i l t er in g. sig n a l le vels w e r e ca lib r a t e d in t o a 50 ? im p e dan c e . analysis t h e c o n v e r s i on g a i n a n d output re f e re nc e are d e r i ve d u s i n g t h e co ef f i cien ts o f a lin e a r r e g r es sion p e r f o r m e d on da t a col l e c t e d in i t s cen t ral o p era t in g ran g e (3 5 mv r m s t o 25 0 mv r m s). this ra n g e was ch os e n t o a v o i d a r e a s o f o p era t io n w h er e o f fs et d i stor t s t h e l i ne ar re sp ons e . e r ror i s st a t e d i n t w o f o r m s e r ror f rom l i ne ar re sp ons e to c w w a ve f o r m an d output d e lt a f rom 2c p e r f o r ma n c e . t h e e r ror f rom l i ne ar re sp o n s e to c w w a ve f o r m i s t h e dif f er en ce i n o u t p u t f r o m t h e i d e a l o u t p ut def i ne d b y t h e c o n v e r s i on g a i n an d output re f e re nc e. t h i s i s a me a s u r e of b o t h th e lin e a r i t y o f th e de v i ce r e s p o n se t o bo th cw a n d m o d u la t e d wa v e fo r m s. th e er r o r in db us es t h e con v ersion ga in m u lt i p lie d by t h e i n put a s it s re f e re nc e. e r ror f rom l i ne ar re sp ons e to c w wa v e fo r m is n o t a m e asur e o f abs o l u te acc u rac y , sin c e i t is c a l c u l a t e d u s i n g t h e g a i n a n d output re f e re nc e o f e a ch d e v i c e . h o w e v e r , i t do es s h o w t h e lin e ar i t y a nd ef f e c t o f m o d u la t i o n o n t h e d e v i c e re s p o n s e . e r ror f rom 2 5 c p e r f or m a nc e u s e s t h e p e r f o r ma n c e o f a g i ven de vic e and wa vefo r m ty p e as t h e re f e re nc e ; it i s pre d om i n a n t l y a me a s u r e of output v a r i a t i o n w i t h te m p e r a t u r e. 1 2 3 4 8 7 6 5 ad8361 vpos iref rfin pwdn sref vrms fltr comm c1 0.1 f r1 75 ? rfin c3 c4 0.1 f c2 100pf iref pwdn vpos sref vrms 01088-c-071 f i gur e 7 1 . char act e r i za tio n boa r d ad8361 characterization board rfin prup +v s sref iref vrms dc output rf signal smiq038b rf source ieee bus pc controller dc matrix / dc supplies / dmm dc sources 3db attenuator 01088-c-072 f i gur e 7 2 . char act e r i za tio n se tup
ad8361 rev. c | page 24 of 24 outline dimensions 0.80 0.60 0.40 8 0 4 85 4.90 bsc pin 1 0.65 bsc 3.00 bsc seating plane 0.15 0.00 0.38 0.22 1.10 max 3.00 bsc coplanarity 0.10 0.23 0.08 compliant to jedec standards mo-187aa f i g u re 73. 8-l e ad m i ni s m al l o u t l ine p a ck ag e [m sop ] (rm-8) di me nsio ns sho w n i n mi ll im e t e r s 1 3 4 5 2 6 2. 90 bs c 1. 60 bs c 2. 80 b s c 1. 90 bs c 0. 95 b s c 0. 22 0. 08 10 4 0 0. 50 0. 30 0 . 1 5 ma x 1. 30 1. 15 0. 90 sea t i n g p l ane 1. 4 5 m a x 0. 60 0. 45 0. 30 pin 1 indicator compliant to jedec standards mo-178ab f i g u re 74. 6-l e ad s m a l l o u t l i n e t r ans i s t or p a ck ag e [so t - 23] (r t - 6) di me nsio ns sho w n i n mi ll im e t e r s ordering guide model temperature r a nge package desc ri ption package option branding ad8361arm ?40c to +85c 8-lead msop, tube rm-8 j3a ad8361arm- r e el ?40c to +85c 8-lead msop, 1 3 " tape and ree l rm-8 j3a ad8361arm- r e el7 ?40c to +85c 8-lead msop, 7 " tape and reel rm-8 j3a ad8361armz 1 ?40c to +85c 8-lead msop, tube rm-8 j3a AD8361ARMZ-REEL 1 ?40c to +85c 8-lead msop, 1 3 " tape and ree l rm-8 j3a ad8361armz-r eel7 1 ?40c to +85c 8-lead msop, 7 " tape and reel rm-8 j3a ad8361art- r ee l ?40c to +85c 6-lead so t-23, 13" tape and re el rt-6 j3a ad8361art- r ee l7 ?40c to +85c 6-lead sot-23, 7" tape and ree l rt-6 j3a ad8361artz-rl7 1 ?40c to +85c 6-lead sot-23, 7" tape and ree l rt-6 j3a ad8361-eval evaluation boar d msop ad8361art- e val evaluation boar d sot-23-6l 1 z = pb-free part. ? 2004 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 . c01088C0 C 8/04(c)

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