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lf to 750 mhz digitally controlled vga ad8370 rev. 0 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 . features programmable low and high g a in (<2 db reso lution) lo w range: ?11 db to +1 7 db high range: +6 db to +34 db differentia l inp u t and output: 200 ? di fferent ial input 100 ? di fferent ial output 7 db noise figure @ maxim u m gain two-tone ip3 of + 3 5 d b m @ 70 mh z ?3 db bandwi d t h of 750 mh z 40 db precision gain range serial 8 - bit digi tal interface wide input dyn a mic range power-down feature single 3 v to 5 v supply applic ati o ns differentia l a d c dri v ers if sampling receivers rf/if gain stages cable and vi de o applications saw filt er inter f acing single-ended-t o-differential conversion general description the ad8370 is a lo w cos t , dig i t a l l y co n t r o l l ed , va r i a b le ga in a m plif ier t h a t pr o v ides p r e c isio n ga in c o n t r o l, hig h ip3, and lo w n o is e f i gur e . the exce l l en t dist or t i o n p e r f o r ma n c e an d wide ba ndwid th ma k e th e ad8370 a s u i t ab le ga in con t r o l de vice f o r m o der n r e cei v e r desig n s. f o r wide in p u t, d y na mic ran g e a p p l ic a t ion s , th e ad8370 p r o - vides tw o i n p u t r a n g es: hig h ga i n m o de and lo w ga in m o d e . a v e r n ier 7-b i t tran s c on d u c t ance (g m) s t a g e p r o v ides 28 db o f ga in r a n g e a t b e t t er t h an 2 db res o l u t i o n , and 22 db o f ga in ra n g e a t bet t er tha n 1 db r e s o l u tio n . a s e con d g a in ra n g e , 17 db hig h er t h a n t h e f i rs t, ca n b e s e le c t e d t o p r o v ide im p r o v e d n o is e pe rf o r m a n c e . the ad8370 is p o w e r e d o n b y a p p l yin g the a p p r o p r i a t e log i c lev e l t o t h e p w up p i n. w h en p o w e r e d do wn, t h e ad8370 co n s u m es les s t h a n 4 ma and of f e rs e x ce l l en t in p u t t o o u t p u t is ola t ion. t h e g a in s e t t i n g is p r es er v e d w h e n op era t i n g i n a p o w e r - do w n mo de. func tio n a l block di agram inhi inlo ophi oplo vcco ocom icom vocm pwup vcco ocom vcci icom bias cell shift register and latches pre amp transconductance output amp 11 6 1 16 4 14 13 12 5 9 8 3 2 10 7 15 data clck ltch ad8370 03692- 0- 001 fi g u r e 1 . 0 10 20 30 40 50 60 70 ?30 ?20 ?10 0 10 20 30 40 voltage gain ( d b) voltage gain ( v /v) 0 1 02 0 3 04 0 6 0 1 0 0 50 70 80 90 110 120 130 gain code 03692-0-003 code = last 7 bits of gain code (no msb) high gain mode high gain mode low gain mode low gain mode ? gain ? code ? 0.409 ? gain ? code ? 0.059 f i gure 2. g a in v s . g a in cod e at 7 0 mh z gain con t r o l o f the ad8 370 is t h rou g h a s e r i a l 8 - bit g a i n c o n t r o l w o r d . th e ms b s e le c t s b e tw e e n t h e tw o ga in ran g es, a nd t h e r e ma inin g 7 b i ts ad j u st t h e o v e r a l l ga in in p r ecis e li n e a r ga in st eps. f a b r ica t ed o n t h e a d i hi g h s p e e d x f c b p r oces s , t h e hi g h ba n d - wid t h o f t h e ad8370 p r ovides hig h f r e q uenc y and low dis t o r tion. the q u ies c en t c u r r en t o f th e ad8370 is 78 ma typ i cal l y . th e ad8370 am p l if ier co m e s in a com p ac t, ther mal l y enha nced 16-le ad t sso p p a cka g e and o p era t es o v er t h e tem p er a t ur e ra n g e o f ?40c t o +85c.
ad8370 rev. 0 | page 2 of 28 table of contents specifications ..................................................................................... 3 absolute maximum ratings ............................................................ 5 esd caution .................................................................................. 5 pin configuration and functional descriptions .......................... 6 typical performance characteristics ............................................. 7 theory of operation ...................................................................... 13 block architecture ...................................................................... 13 preamplifier ................................................................................. 13 transconductance stage ............................................................ 13 output amplifier ........................................................................ 14 digital interface and timing .................................................... 14 applications ..................................................................................... 15 basic connections ...................................................................... 15 gain codes .................................................................................. 15 power-up feature ....................................................................... 15 choosing between gain ranges ............................................... 15 layout and operating considerations .................................... 16 package considerations ............................................................. 17 single-ended-to-differential conversion ............................... 17 dc-coupled operation ............................................................. 18 adc interfacing ......................................................................... 19 3 v operation ............................................................................. 20 evaluation board and software .................................................... 21 appendix ......................................................................................... 24 characterization equipment ..................................................... 24 composite waveform assumption .......................................... 24 definitions of selected parameters .......................................... 24 outline dimensions ....................................................................... 28 ordering guide .......................................................................... 28 revision history revision 0: initial version
ad8370 rev. 0 | page 3 of 28 specifications v s = 5 v, t = 25c, z s = 200 ?, z l = 100 ? at gain code hg127, 70 mhz, 1 v p-p differential output, unless otherwise noted. table 1. parameter conditions min typ max unit dynamic performance ?3 db bandwidth v out < 1 v p-p 750 mhz slew rate gain code hg127, r l = 1 k?, ad8370 in compression 5750 v/ns gain code lg127, rl = 1 k?, v out = 2 v p-p 3500 v/ns input stage pins inhi and ihlo maximum input gain code lg2, 1 db compression 3.2 v p-p input resistance differential 200 ? common-mode input range 3.2 v p-p cmrr differential, f = 10 mhz, gain code lg127 77 db input noise spectral de nsity 1.9 nv/hz gain maximum voltage gain high gain mode gain code = hg127 34 db 52 volts/volt low gain mode gain code = lg127 17 db 7.4 volts/volt minimum voltage gain high gain mode gain code = hg1 ?8 db 0.4 volts/volt low gain mode gain code = lg1 ?25 db 0.06 volts/volt gain step size high gain mode 0.408 (volts/volt)/code low gain mode 0.056 (volts/volt)/code gain temperature sensitivity gain code = hg127 C2 mdb/ c step response for 6 db gain st ep, settled to 10% of final value 20 ns output interface pins ophi and oplo output voltage swing r l 1 k? (1 db compression) 8.4 v p-p output resistance differential 95 ? output differential offset v inhi = v inlo , over all gain codes 60 mv noise/harmonic performance 10 mhz gain flatness within 10 mhz of 10 mhz 0.01 db noise figure 7.2 db second harmonic 1 v out = 2 v p-p ?77 dbc third harmonic 1 v out = 2 v p-p ?77 dbc output ip3 35 dbm output 1 db compression point 17 dbm see footnotes on next page.
ad8370 rev. 0 | page 4 of 28 parameter conditions min typ max unit noise/harmonic performance (cont.) 70 mhz gain flatness within 10 mhz of 70 mhz 0.02 db noise figure 7.2 db second harmonic 1 v out = 2 v p-p ?65 dbc third harmonic 1 v out = 2 v p-p ?62 dbc output ip3 35 dbm output 1 db compression point 17 dbm 140 mhz gain flatness within 10 mhz of 140 mhz 0.03 db noise figure 7.2 db second harmonic 1 v out = 2 v p-p ?54 dbc third harmonic 1 v out = 2 v p-p ?50 dbc output ip3 33 dbm output 1 db compression point 17 dbm 190 mhz gain flatness within 10 mhz of 240 mhz 0.03 db noise figure 7.2 db second harmonic 1 v out = 2 v p-p ?43 dbc third harmonic 1 v out = 2 v p-p ?43 dbc output ip3 33 dbm output 1 db compression point 17 dbm 240 mhz gain flatness within 10 mhz of 240 mhz 0.04 db noise figure 7.4 db second harmonic 1 v out = 2 v p-p C28 dbc third harmonic 1 v out = 2 v p-p C33 dbc output ip3 32 dbm output 1 db compression point 17 dbm 380 mhz gain flatness within 10 mhz of 240 mhz 0.04 db noise figure 8.1 db output ip3 27 dbm output 1 db compression point 14 dbm power-interface supply voltage 3.0 2 5.5 v quiescent current 3 pwup high, gc = lg127, r l = , 4 seconds after power-on, thermal connection made to exposed paddle under device 72.5 79 85.5 ma vs. temperature 4 ?40c t a +85c 105 ma total supply current pwup high, v out = 1 v p-p, z l = 100 ? reactive, gc = lg127 (includes load current) 82 ma power down current pwup low 3.7 ma vs. temperature 4 ?40c t a +85c 5 ma power up interface pin pwup power-up threshold 4 voltage to enable the device 1.8 v power-down threshold 4 voltage to disable the device 0.8 v pwup input bias current pwup = 0 v 400 na gain control interface pins clck, data, and ltch v ih 4 voltage for a logic high 1.8 v v il 4 voltage for a logic low 0.8 v input bias current 900 na 1 refer to for perfor mance into a lighter load. figure 20 2 see the sect ion for more information. 3 v operation 3 minimum and maximum specified limits for this pa rameter are guaranteed by production test. 4 minimum or maximum specified limit for this parameter is a 6-sigma value and not guara nteed by production test.
ad8370 rev. 0 | page 5 of 2 8 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 pwup, data, c l ck, ltch v s + 500 mv differential input voltage, v inhi C v inlo 2 v common-mode input vol t age, v inhi or v inlo, with respe c t to icom or ocom v s + 500 mv (maximum), v icom C 500 mv, v ocom C 500 mv (minimum) internal power dissipation 575 mw ja (ex pos ed paddl e s o l d ered dow n ) 30c/ w ja (exp ose d pa ddl e no t sol d ered do wn ) 9 5 c / w jc (at exposed paddle) 9c/w maximum junction temperature 150c operating temperature range C40c to +85c storage temperature range C65c to +150c lead temperature range (soldering 60 sec) 235c s t r e s s es a b o v e t h os e list e d u n der a b s o l u t e m a xim u m r a t i n g s ma y c a us e p e r m a n en t da ma g e t o t h e de vice. t h i s i s a st re ss r a t i ng on ly ; f u nc t i on a l op e r a t i o n of t h e d e v i c e a t t h e s e or an y ot he r c o n d i t i o n s a b ove t h o s e list e d in t h e o p era t io na l s e c t ion s o f t h is sp e c i f ica t ion is n o t im pli e d . e x p o sur e t o a b s o l u t e maxi 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 vi ce rel i a b i l it y . esd c a ution esd (electrostatic discharge) sensitive device. ele c trosta tic charg e s as high as 4000 v readily accumulate on the human body and test eq uipment and can discharge with out 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.
ad8370 rev. 0 | page 6 of 2 8 pin conf igura t ion and fu nctional descri ptions 6 7 8 11 10 9 ad8370 top view (not to scale) 2 3 4 5 15 14 11 6 13 12 03692-0-002 inhi icom vcci pwup vocm vcco o com ophi oplo ocom vcco ltch clck data icom inlo f i gure 3.16-l ead t ssop ta ble 3. pi n f u nct i on d e s c ri pt i o ns pin no. mnemonic description 1 i n h i balanced differential input. internally biased. 2, 15, paddle icom input common. connect to a low impedance gr ound. this node is als o conne cted to the expose d pad on the bottom of the device. 3 vcci input positive supply. 3.0 v to 5.5 v. should be proper l y bypas s e d. 4 pwup power enable pin. device is op er ational when p w up is pulled high. 5 v o c m common-mode output voltag e pin. the midsu pply ((v vcco ? v oc o m )/2) common - mode voltage i s delivered to this pin for exter n al bypa ssing fo r additional com m on -mode sup p ly decoupling. this can be ac hi eved with a bypass c a pa cito r to ground. t h is pin is a n outp ut only and is not to be driven ex ternally. 6, 11 vcco output positive supply. 3.0 v to 5.5 v. should be properly byp a s s ed. 7, 10 ocom output common. connect to a low impedance ground. 8 ophi balanced differential o utput. biased to midsupply. 9 oplo balanced differential o utput. biased to midsupply. 1 2 l t c h serial data latch pin. serial data is clocked into the shift register via the data p i n when ltch is low. data in shift register is l a tched on the next high-going edge. 13 clck serial clock input pin. 14 data serial data inpu t pin. 1 6 i n l o balanced differential input. internally biased.
ad8370 rev. 0 | page 7 of 2 8 typical perf orm ance cha r acte ristics v s = 5 v , z s = 200 ?, z l = 100 ?, t = 25c, unles s o t h e r w is e no t e d . 0 10 20 30 40 50 60 70 ?30 ?20 ?10 0 10 20 30 40 voltage gain ( d b) voltage gain ( v /v) 0 1 02 0 3 04 0 6 0 1 0 0 50 70 80 90 110 120 130 gain code 03692-0-003 code = last 7 bits of gain code (no msb) high gain mode high gain mode low gain mode low gain mode ? gain ? code ? 0.409 ? gain ? code ? 0.059 f i gure 4. g a in v s . g a in cod e at 7 0 mh z 5 10 15 20 25 30 35 40 output ip3 ( d bm) ?5 0 5 10 15 20 25 30 outp ut ip 3 (dbv rms ) 0 2 0 4 0 6 0 8 0 100 120 140 gain code 03692-0-024 high gain mode low gain mode shading indicates 3 from the mean. data based on 30 parts from two batch lots. f i gure 5. o u tput th ir d- o r der in t e r c ept vs . g a in code at 70 mhz 5 10 15 20 25 30 nois e figure (db) 35 40 45 0 2 0 4 0 6 0 8 0 100 120 140 gain code 03692-0-012 high gain mode 380 mhz 380 mhz 70 mhz 70 mhz low gain mode f i g u re 6. n o is e f i g u r e v s . g a in code at 70 m h z ?10 ?5 0 5 10 15 20 25 30 35 40 voltage gain ( d b) frequency (mhz) 10 100 1000 03692-0-072 hg77 hg127 lg90 lg9 lg18 lg127 hg102 hg18 lg36 hg51 hg25 hg9 hg3 high gain codes shown with dashed lines low gain codes shown with solid lines f i gur e 7 . f r equenc y resp o n se vs . g a in c o d e 10 15 20 25 30 35 40 outp ut ip 3 (dbm) +2 5c 20 25 30 35 40 45 50 ou tpu t ip3 ( d b m ) ?40 c , + 8 5 c 200 150 5 0 100 0 2 5 0 30 0 350 40 0 frequency (mhz) 03692-0-026 +25c unit conversion note for 100 ? load: dbvrms = dbm ? 10db +85 c ?40 c shading indicates 3 from the mean. data based on 30 parts from two batch lots. f i g u r e 8 . ou t p u t t h i r d - or d e r i n t e r c e p t vs . f r e q u e n c y a t ma x i m u m g a i n 0 5 10 15 20 25 nois e figure (db) 200 300 0 100 400 500 600 frequency (mhz) 03692-0-011 hg18 hg127 lg127 fi g u r e 9 . n o i s e fi g u r e v s . fr e q u e n c y a t v a r i o u s g a i n s
ad8370 rev. 0 | page 8 of 2 8 ?8 ?4 0 4 8 12 16 20 outp ut p 1 db (db) 0 2 0 4 0 6 0 8 0 100 120 140 gain code 03692-0-028 shading indicates 3 from the mean. data based on 30 parts from two batch lots. unit conversion note: for 100 ? load: dbvrms = dbm? 10db for 1k ? load: dbvrms = dbm low gain mode low gain mode high gain mode 100 ? load 1k ? load high gain mode f i gure 10. o u tput p 1 db v s . g a in code at 7 0 m h z ?8 5 ?8 0 ?7 5 ?7 0 ?6 5 ?6 0 ?5 5 outp ut imd (dbc ) 0 2 0 4 0 6 0 8 0 100 120 140 gain code 03692-0-027 shading indicates 3 from the mean. data based on 30 parts from two batch lots. low gain mode high gain mode f i gure 11. t w o - t o n e o u tput imd3 v s . g a in cod e at 7 0 m h z, r l = 1 k?, v ou t = 1 v p -p com p os it e d i f f e r e nt ia l ?2.0 ?1.5 ?1.0 ?0.5 0 0.5 gain e rror (db) 1.0 1.5 2.0 frequency (mhz) 10 100 1000 03692-0-007 ?40 c +85 c error at ?40c and +85c with respect to 25c. shading indicates 3 from the mean. data based on 30 parts from one batch lot. f i gure 12. g a in e r ror o v er t e mpe r atu r e v s . f r equ e nc y , r l = 100 ? 6 8 10 12 14 16 18 20 ou tpu t p1db ( d b m ) ? 40 c , + 85c 4 6 8 10 12 14 16 18 output p1db (dbm) +25 c 20 0 150 5 0 100 0 2 50 300 350 400 frequency (mhz) 03692-0-083 shading indicates 3 from the mean. data based on 30 parts from two batch lots. unit conversion note: re 100 ? load: dbvrms = dbm ? 10db re 1k ? load: dbvrms = dbm +25c, 100 ? load +25c, 1k ? load +85 c, 100 ? load +85c, 1k ? load ?40c, 100 ? load ?40c, 1k ? load fi g u r e 1 3 . o u t p u t p 1 d b v s . fr e q u e n c y ?9 4 ?9 2 ?8 8 ?8 0 ?7 6 ?7 2 ?7 0 ?6 8 ?8 4 ?9 0 ?8 2 ?7 8 ?7 4 ?8 6 outp ut imd (dbc ) +2 5 c ?8 6 ?8 4 ?8 0 ?7 2 ?6 8 ?6 4 ?6 2 ?6 0 ?7 6 ?8 2 ?7 4 ?7 0 ?6 6 ?7 8 outp ut imd (dbc ) ? 4 0 c, +8 5c 20 0 15 0 50 1 0 0 0 250 300 35 0 400 frequency (mhz) 03692-0-030 shading indicates 3 from the mean. data based on 30 parts from two batch lots. +25c +85 c ?40 c f i gure 14. t w o - t o n e o u tput imd3 v s . f r equ e nc y at maxi m u m g a in , r l = 1 k ? , v ou t = 1 v p -p co mpos ite d i f f e r e nt i a l ?2.0 ?1.5 ?1.0 ?0.5 0 0.5 gain e rror (db) 1.0 1.5 2.0 frequency (mhz) 10 100 1000 03692-0-006 error at ? 4 0 c and +85c with respect to 25 c. shading indicates 3 from the mean. data based on 30 parts from one batch lot. ?40 c +85 c f i gure 15. g a in e r ror o v er t e mpe r atu r e v s . f r equ e nc y , r l = 1 k?
ad8370 rev. 0 | page 9 of 2 8 ?90 ?80 ?70 ?60 ?50 ?40 ?30 ?20 ?10 0 harmonic dis t ortion (dbc ) 0 2 0 4 0 6 0 8 0 100 120 140 gain code 03692-0-057 high gain, r l = 1k ? low gain, r l = 1k ? low gain, r l = 100 ? high gain, r l = 100 ? f i gure 16. s e c o nd- o r d er h a r m o n i c d i stor t i on v s . g a in code at 7 0 m h z, v ou t = 2 v p -p d i ffer e ntial 1ghz 5mhz s 22 s 11 0 180 30 330 60 90 270 300 120 240 150 210 03692-0-059 f i gure 1 7 . input a n d o u tput refl ection c o effi cients , s 11 and s 22 , z o = 1 00 ? d i f f e ren t ial 0 50 100 150 200 250 re s i s t ance ( ? ) ? 150 ? 100 ?5 0 0 50 100 re actance (j ? ) 0 100 200 300 400 500 600 700 frequency (mhz) 03692-0-031 16 different gain codes represented r+jx format f i g u re 18. input r e s i s t anc e and r e ac t a nc e v s . f r equ e nc y ?90 ?80 ?70 ?60 ?50 ?40 ?30 ?20 ?10 0 harmonic dis t ortion (dbc ) 0 2 0 4 0 6 0 8 0 100 120 140 gain code 03692-0-036 low gain r l = 100 ? low gain r l = 1k ? high gain r l = 100 ? high gain r l = 1k ? f i gure 19. thi r d- o r der ha rm on ic d i stor t i o n v s . g a i n cod e at 70 mh z, v ou t = 2 v p -p d i ffer e ntial ?90 ?80 ?70 ?60 ?50 ?40 ?30 ?20 ?10 0 harmonic dis t ortion (dbc ) 20 0 15 0 50 10 0 0 2 50 300 350 400 frequency (mhz) 03692-0-029 hd 2 r l = 100 ? hd 3 r l = 100 ? hd 3 r l = 1k ? hd 2 r l = 1k ? f i gur e 2 0 . ha rm onic di stor ti on vs . f r eque nc y a t m a xim u m g a i n , v ou t = 2 v p -p com p os it e d i f f e r e nt ia l 0 20 40 60 80 100 120 re s i s t ance ( ? ) ?40 ?20 0 20 40 60 80 re actance (j ? ) 0 100 200 300 400 500 600 700 frequency (mhz) 03692-0-033 16 different gain codes represented r+jx format f i gur e 2 1 . o u tput resi sta n c e and rea c ta nc e vs . f r equenc y
ad8370 rev. 0 | page 10 of 28 700 720 740 760 780 800 group delay ( p s) 820 840 860 0 1 02 0 3 04 0 6 0 1 0 0 50 70 80 90 110 120 130 gain code 03692-0-032 high gain mode low gain mode f i gure 22. group d e l a y v s . g a in cod e at 7 0 m h z 20 30 40 50 60 70 80 90 100 110 120 p s rr (db) frequency (mhz) 1 100 10 1000 03692-0-013 f i gure 23. p o wer s u p p ly rej e c t ion rat i o vs. f r equ e nc y at maxim u m g a in ?120 ?100 ?8 0 ?6 0 ?4 0 ?2 0 0 is olation (db) frequency (mhz) 10 100 1000 03692-0-009 forward transmission, hg0 reverse transmission, hg127 forward transmission, lg0 forward transmission, pwup low f i g u re 24. v a r i ous f o r m s of is ol at i o n v s . f r equenc y 600 700 800 900 1000 1100 group delay ( p s) 1200 1300 1400 0 100 200 300 400 500 600 700 800 900 frequency (mhz) 03692-0-034 r l = 1k ? r l = 100 ? f i gure 2 5 . gro u p d e la y vs . f r equ e nc y a t ma xim u m g a i n 0 10 20 30 40 50 cmrr (db) 60 70 80 frequency (mhz) 10 100 1000 03692-0-005 hg32, hg127 lg32, lg127 f i g u re 26. co m m o n -m ode r e jec t ion rat i o v s . f r equenc y 0 2 4 8 10 12 n o ise spec tr a l d e n s ity ( n v/ h z ) 6 210 310 10 110 410 510 610 frequency (mhz) 03692-0-010 hg18 hg127 lg127 f i gure 27. input r e f e rred n o is e spe c t r a l d e ns i t y v s . f r equenc y a t v a rious g a i n s
ad8370 rev. 0 | page 11 of 28 time (2ns/div) volta ge ( 6 00mv/d i v) gnd 03692-0-067 differential v in differential v out v oplo v ophi f i g u re 28. dc- c ou pled l a r g e sig n al p u ls e r e s p ons e 03692-0-068 pwup (2v/div) time (40ns/div) gnd zero input = ? 30dbm, 70mhz 100 averages gain code hg127 differential output (50mv/div) f i gur e 2 9 . pw up t i m e d o mai n re sponse 03692-0-035 ltch (2v/div) time (20ns/div) gnd zero input = ? 30dbm, 70mhz no averaging 6db gain step (hg36 to lg127) differential output (10mv/div) f i gure 30. g a in ste p t i me d o ma in res p onse time (2ns/div) volta ge ( 1 v/d i v) 03692-0-069 gnd v out differential f i gure 31. o v e r dr ive r eco ver y 50 55 60 65 70 75 80 85 s u p p ly curre nt (ma) 64 48 16 32 0 8 0 9 6 112 128 gain code 03692-0-014 high gain low gain f i gure 32. sup p l y current v s . g a in cod e 0 5 10 15 20 25 30 35 count 50 51 52 53 54 55 gain (v/v) 03692-0-073 data from 136 parts from one batch lot mean: 51.9 : 0.518 f i g u re 33. d i s t r i but i on of v o lt ag e g a in , hg 12 7, 70 m h z, r l = 100 ?
ad8370 rev. 0 | page 12 of 28 2.40 2.45 2.50 2.55 2.60 2.65 2.70 2.75 v cm (v ) 0 96 32 64 0 3 2 6 4 9 6 128 gain code 03692-0-071 +25 c +85 c ?4 0 c low gain mode high gain mode f i g u re 34. co m m o n -m ode o u t p ut v o l t ag e v s . g a i n code at v a ri ous t e mper at u r es
ad8370 rev. 0 | page 13 of 28 theor y of opera tion the ad8370 is a lo w cos t , dig i t a l l y co n t r o l l ed , f i ne ad j u s t m e n t va r i a b le ga in am p l if ier tha t p r o v ides bo t h hig h ip3 an d lo w n o is e f i gur e . the ad8370 is fab r ica t e d o n an ad i p r o p r i eta r y hig h p e r f o r ma n c e 25 gh z silicon b i p o l a r p r o c ess. th e C3 db ba ndwid th is a p p r o x ima t e l y 750 mh z thr o ug h o u t the va r i ab le ga in ra n g e . th e typ i cal q u ies c en t c u r r en t o f th e ad8370 is 78 ma. a p o w e r - do w n fe a t ur e r e d u ces t h e c u r r en t t o les s t h an 4 ma. t h e in put im p e dan c e is a p p r o x ima t e l y 2 00 ? dif f er en t i a l , a nd t h e o u t p u t im p e dance is a p p r o x ima t e l y 100 ? dif f er en tial to b e com p a t i b l e wi t h s a w f i l t ers a nd m a tchi n g netw o r k s us e d i n in t e r m e d i a t e f r e q uen c y (if) rad i o a p plic a t io n s . b e ca us e t h er e is n o fe e d b a ck b e t w e e n t h e i n p u t a nd o u t p u t and st a g es w i t h i n t h e a m plif ier , t h e in p u t am plif ier is is ola t e d f r o m var i a t io n s in o u t p ut lo adin g a nd f r o m sub s e q uen t i m p e d a nce cha n ges, and exce l l en t in p u t to o u t p u t is ola t i o n is r e a l i z e d . e x ce l l en t dist o r - tio n p e r f o r ma nce an d wide band wid t h ma k e t h e ad8370 a s u i t ab le ga in con t r o l de vice f o r m o der n dif f er en tial r e cei v er des i g n s. the ad8370 dif f eren t i al in p u t and ou t p u t conf igur a t ion is ide a l l y s u i t e d t o f u l l y dif f er en tial sig n al c h ain cir c ui t desig n s, a l t h ou g h i t c a n b e a d a p t e d to s i ng l e - e nd e d s y st e m a p pl i c a t i o ns , if r e q u ir e d . bl ock ar chitec ture the thr e e b a sic b u ildin g b l o c ks o f th e ad8370 a r e a hig h /lo w ga in s e le c t a b le in p u t p r e a m p lif i er , a dig i tal l y con t r o l l e d tra n sco n d u ct a n ce (g m ) b l o c k, and a f i xe d ga i n o u t p ut st a g e. inhi inlo ophi oplo vcco ocom icom vocm pwup vcco ocom vcci icom bias cell shift register and latches pre amp transconductance output amp 11 6 1 16 4 14 13 12 5 9 8 3 2 10 7 15 data clck ltch ad8370 03692- 0- 001 f i g u re 35. f u nc t i o n al bl ock d i ag r a m preamplifier ther e a r e tw o s e le c t a b le in p u t p r e a m p lif i ers. s e le c t io n is made b y t h e m o st sig n if ican t b i t (msb) o f t h e s e r i a l ga in con t r o l d a t a - w o r d . i n t h e h i g h ga in mo de , t h e o v era l l de vic e ga in is 7.1 v o l t s / v o l t (17 db) a b o v e t h e lo w ga in s e t t i n g. the two p r e a m p lif i ers g i v e the ad837 0 th e ab ili t y t o acco mm o d a t e a wide ra n g e o f in p u t a m pl i t ude s . th e o v erl a p b e tw e e n t h e t w o ga in ra n g es a l lo ws t h e us er s o me f l ex i b i l i t y b a s e d o n n o is e a nd disto r t i o n deman d s. s e e t h e c h o o sin g b e t w e e n g a i n r a nges s e c t io n fo r more i n for m a t i o n . the in p u t im p e dan c e is a p p r o x ima t e l y 200 ? dif f er en tial , re g a rd l e ss o f whi c h p r ea m p li f i er i s se lec t e d . n o t e tha t th e i n p u t i m ped a n c e is for m e d b y usin g a c t i v e cir c ui t e l em e n ts and is n o t s e t b y pas s i v e co m p o n en ts . s e e f i gur e 36 f o r a s i m p l i f i e d sc h e m a t i c o f t h e in p u t in t e r f ace . 1ma 1ma vc c / 2 2k ? in h i /in lo 03692-0-018 f i g u re 36. inh i /inl o si mpl i f i ed s c he mat i c tr ansc onduc t ance st a g e t h e d i g i tall y c o n t r o ll ed g m s e c t io n has 42 db o f co n t r o l l a b le ga in and ma k e s ga in t h e ad j u s t m e n t s wi thin eac h ga in ran g e . the s t ep s i ze r e s o l u t i o n ra n g es f r o m a f i n e ~ 0. 07 db u p t o a co a r s e 6 db p e r b i t, dep e ndin g on t h e ga in co de. a s sh o w n i n f i gur e 37, o f th e 42 db t o tal rang e , 28 db has r e s o l u tio n o f b e t t er t h an 2 db , a n d 22 db has r e s o l u t i o n o f b e t t er t h an 1 db . the c u r v es in f i gur e 37 s h o w ty p i cal in p u t l e v e l s tha t c a n be a p plie d t o t h is am plif ier a t dif f er en t ga i n s e t t in g s . th e maxi- m u m i n p u t was deter m i n e d b y f i ndin g t h e 1 db co m p r e ssio n o r e x pa n s i o n po in t o f th e v ou t /v so ur c e ga in. n o te t h a t t h is is n o t v ou t /v in . i n th is w a y , th e c h a n ge i n t h e in p u t im pe d a n c e o f th e de vice is a l s o t a k e n in to acco un t. 0 0.4 0.8 1.2 1.6 2.0 v out [ v peak] ( v ) 2.4 2.8 3.2 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 v source [v peak] (v) 03692-0-023 high gain 0.1db gain ?5db gain ? 8db gain 12db gain 6db gain <2db res <2db res <1db res <1db res <0.5db resolution <0.5db res ? 11db gain 17db gain 34db gain ? 25db gain low gain f i g u re 37. g a in r e s o lut i on and no m i n a l i n put a n d o u tput range o v er the g a in rang e
ad8370 rev. 0 | page 14 of 28 outpu t am plifier table 4. serial programming timing parameters parameter min unit clock pulse wid t h (t pw ) 25 ns clock peri od (t ck ) 50 ns setup t ime data vs. cloc k (t ds ) 10 ns setup time latc h vs. clock (t es ) 20 ns hold time latch vs. clock (t eh ) 10 ns the o u t p u t im p e dan c e is a p p r o x ima t e l y 100 ? dif f er en tial an d , li k e t h e in pu t p r e a m p lif i er , t h is i m p e dance is fo r m e d usin g a c ti v e ci r c ui t e l em en t s . s e e f i gur e 38 f o r a s i m p l i f i ed sch e ma ti c of t h e output i n te r f a c e. vc c / 2 74 0 ? o p h i/o p l o 03692-0-019 10 a c l ck / dat a/ l t ch/ p w up 03692-0-017 f i gure 38. ophi/o pl o simplified cir c u i t f i gure 40. si mpl i fi e d circuit f o r d i git a l inputs the ga in o f th e o u t p u t a m p l if ier , a n d t h us the ad8370 as a wh o l e , i s l o a d de pen d en t . th e fo ll o w i n g eq ua tio n ca n be used t o p r edic t t h e ga in de via t ion o f the ad8370 f r o m tha t a t 100 ? as th e loa d i s v a ri e d : v cc / 2 75 ? vo c m 03692-0-020 load r ion gaindeviat 98 1 98 . 1 + = fo r e x a m p l e , i f r loa d is 1 k ? , the ga in i s a f a ct o r o f 1. 8 0 ( 5 .1 2 db) ab o v e tha t a t 10 0 ?, al l o t h e r thin gs bein g e q ual. i f r loa d is 50 ?, th e ga in is a f a c t o r o f 0.669 (3.4 9 db) be lo w tha t a t 100 ?. f i gure 41. si mpl i fi e d circuit f o r vo c m o u tput digit a l in t e rf a c e an d tim i ng the dig i t a l con t r o l p o r t us es a s t a n da r d t t l i n t e r f ace . th e 8- b i t co n t r o l w o r d is r e ad in a s e r i a l f a shion w h e n t h e l t ch pin is h e l d lo w . th e le v e l s p r es en te d to t h e d a t a p i n a r e r e ad o n e a ch r i sin g e d g e o f th e c l ck sig n al . f i gur e 39 il l u s t ra t e s t h e timin g di ag r a m fo r t h e c o n t r o l in ter f ac e. mini m u m v a lu es fo r t i ming p a ra m e ters a r e p r es en t e d i n t a b l e 4. f i gur e 40 is a sim p lif i e d sc h e ma ti c o f t h e d i gi tal in p u t p i n s . dat a (pin 14) clc k (pin 13) ltch (pin 12) t ds t es t eh msb msb-1 msb-2 msb-3 lsb lsb+1 lsb+2 lsb+3 t ck t pw 03692-0-038 f i gu r e 3 9 . di gi ta l t i m i n g dia g r a m
ad8370 rev. 0 | page 15 of 28 appli c a t ions b a sic c o nnec t io n s f i gur e 42 s h o w s th e minim u m c o nn ec t i o n s r e q u ir ed f o r basic o p era t ion o f th e ad8370. s u p p l y v o l t a g es betw e e n 3.0 v and 5.5 v a r e al lo w e d . th e s u p p l y t o th e v c c o an d v c ci p i n s s h o u ld b e de cou p le d wi t h a t le as t on e lo w ind u c t a n c e , s u r f ace- m o u n t cera mic ca p a c i t o r o f 0.1 f p l aced as c l os e as p o s s i b le t o th e de v i ce . ad8370 inhi icom vc c i pw u p voc m vc c o ocom ophi oplo ocom v cco ltch clck data icom inlo 67 8 23 5 1 11 10 9 15 14 16 13 12 4 serial control interface 0.1 f 1nf 0.1 f +v s (3.0v to 5.0v) 1nf 1nf 1nf 1nf balanced load r l balance d source r s 2 r s 2 03692-0-037 f i gure 42. bas i c connec t ions the ad8370 is desig n e d t o be us ed in dif f er en tial sig n al c h ains. di f f er en ti al si g n ali n g allo w s im p r o v ed even-o r d er h a rm o n i c can c e l l a tion and b e t t e r co mm on -m ode i m m u ni t y th a n ca n be achie v e d usin g a sin g le-e nde d desig n . t o f u l l y ex plo i t t h es e b e n e f i t s , i t is n e cess a r y to dr i v e a nd lo ad t h e d e vice in a b a lan c e d manner . this r e q u ir es s o m e ca r e t o ens u r e t h a t t h e co mm o n - m o d e im p e dan c e val u es p r es en t e d t o e a ch s e t o f in p u ts an d ou t p u t s a r e b a l a n c e d . dr i v in g t h e d e vice w i t h an un b a lan c e d s o u r ce ca n deg r ade t h e co m m o n - m o d e r e j e c t ion ra t i o . l o adi n g t h e d e vice w i t h an un b a lance d lo ad can c a us e deg r ad a t ion to e v en -o r d er ha r m o n ic disto r t i on an d p r ema t ur e ou t p ut c o m p re ss ion. i n ge ne r a l, op t i m u m de s i g n s are f u l l y b a lan c e d , al t h oug h t h e a d 837 0 s t i l l p r o v ides i m p r es si v e pe rf o r m a n c e w h en used in a n un bal a n c e d en vi r o n m en t. the ad8370 is a f i ne ad j u s t m e n t , va r i ab le ga in a m p l if ier . th e ga i n co n t r o l tra n sf e r fun c ti o n is li n e a r in v o l t a g e ga i n . on a d e ci be l scale , thi s r e s u l t s i n t h e loga ri th m i c tra n sf e r fun c ti o n s indic a te d i n f i g u r e 4. a t t h e lo w end o f t h e ga i n t r a n sfer f u n c t i on, t h e slo p e is st e e p , p r o v idin g a ra t h er c o a r s e co n t r o l fun c ti o n . a t th e h i gh en d o f th e ga i n co n t r o l ra n g e , th e d e ci b e l s t ep size de cr e a s e s, al lo win g p r e c is e ga in ad j u stm e n t . gain c o des the ad8370 s tw o ga in ra n g es a r e r e f e r r ed t o as hig h ga in (h g ) a nd lo w ga in (lg). w i thin each ra n g e , th er e a r e 128 p o s s i b le ga in co des. th e r efo r e , t h e mini m u m ga i n i n t h e lo w ga in ra n g e is g i v e n b y t h e no m e n c la t u r e l g 0 w h er e a s t h e maxim u m ga in in tha t ra n g e is g i v e n b y l g 127. the s a m e is tr ue f o r th e hig h ga in ra n g e . b o t h lg0 and h g 0 ess e n t ia l l y t u r n o f f t h e va r i a b le t r ans c ond u c t a n c e st ag e, a n d t h u s no out p ut i s a v ai l a bl e w i t h t h es e c o des. s e e f i gur e 24. the t h e o r e tical lin e a r v o l t a g e g a in c a n be exp r e s s e d wi th r e s p e c t t o th e ga in co de as a v = g a i n c o de v e r n i e r( 1 + ( pr eg a i n ? 1) msb) w h er e: a v i s t h e l i n e ar volt age g a i n . ga i n co d e is t h e dig i t a l gain con t r o l w o r d min u s t h e ms b (t h e fi n a l 7 b i t s ) . ve r n i e r = 0.055744 v/v pr eg a i n = 7.079 458 v/v msb is t h e m o st sig n if ican t b i t o f t h e 8- b i t gain co n t r o l w o r d . the ms b s e ts t h e de vice in e i t h er hig h ga in mo de (ms b = 1 ) o r lo w ga in mo de ( m s b = 0). f o r exa m p l e , a ga in con t r o l w o r d o f h g 45 (o r 10101101 b i na r y ) r e s u l t s in a theor e tical lin e a r v o l t a g e ga in o f 17.76 v o l t s/v o l t , calc u l a t ed as 45 0.055744 (1 + (7.079458 ? 1) 1) i n cr em en t s o r decr e m en t s in ga i n w i thi n ei t h e r ga i n ra n g e a r e s i m p ly a m a tte r of op e r a t i n g o n t h e ga i n c o d e . s i x C d b g a i n s t eps, which a r e e q ui valen t t o do u b lin g o r halvin g th e l i n e a r v o l t a g e ga in, a r e acco m p lish e d b y do u b lin g o r hal ving the g a i n c ode . w h en p o w e r is f i rs t a p p l ie d t o t h e ad8370, t h e de vice is p r o g r a mm e d to co de lg0 to a v o i d o v er dr i v in g t h e cir c ui t r y fol l o w ing it. po wer-up fea t ure the p o w e r - u p fe a t ur e do es n o t a f fe c t t h e ga i n co d e an d t h e gain s e t t in g is p r es er v e d w h e n i n p o w e r - do w n m o de . p o w e r i n g do wn t h e ad83 70 (b r i n g in g p w up lo w w h ile p o w e r is s t il l a p plie d t o t h e de v i ce) do es n o t eras e o r cha n g e t h e ga i n c o d e f r o m t h e ad83 70, a n d t h e s a me ga in co de is i n place w h e n t h e de vice is p o w e r e d u p , t h a t is, w h e n pw up is b r o u g h t hig h a g a i n. re m o vi ng p o w e r f r o m t h e d e vice a l l to get h er and re a p p l y i n g , how e ve r , re pro g r a ms to lg 0 . choosing be t w een gain r a nges ther e is s o m e o v erla p b e tw e e n t h e tw o ga in ran g es; us ers ca n ch o o s e w h ich on e is m o s t a p p r o p r i a t e fo r t h eir n e e d s. w h en d e c i d i ng w h i c h pre a m p to u s e, c o ns i d e r re s o lut i on , noi s e, l i ne ar it y , a n d spu r i o u s - f re e dy n a m i c r a nge ( s f d r ) . t h e mo s t im p o r t an t p o in t s t o k e ep in m i nd a r e ? the lo w ga in ran g e has b e t t er g a in r e s o l u t i on. ? the hig h ga in ra n g e has a b e t t e r n o is e f i gur e .
ad8370 rev. 0 | page 16 of 28 ? the hig h ga i n ra n g e has b e t t er l i n e a r i t y an d s f d r a t hig h er ga in s. ? c o n v ers e l y , t h e lo w ga in ra n g e has hig h er s f dr a t lo w e r ga in s. f i gur e 43 p r o v ides a s u mma r y o f n o is e , o i p3, iip3, a nd s f d r as a f u n c t i o n o f de vice p o w e r ga in. s f dr is def i n e d as () s n nf iip sfdr ? ? = 3 3 2 w h er e: iip3 i s th e i n p u t th i r d - o r d e r in t e r c e p t po in t , t h e o u t p u t i n t e r c e p t po in t in d b m m i n u s th e ga in in db . nf is t h e n o is e f i gur e in d b . n s is s o ur ce r e sis t o r n o is e , C174 db m f o r a 1 h z ba ndwid th a t 300 k (27 c) . in g e n e r a l , n s = 10 log 10 (ktb), w h er e k = 1.374 1 0 ?23 , t i s t h e t e m p era t ur e in deg r e e s k e l v in, a nd b is t h e n o i s e b a n d wi d t h in he r t z . 30 20 10 0 10 20 nois e figure (db), oip 3 and iip 3 (dbm) 30 40 50 100 110 120 130 140 150 s f dr (db) 160 170 180 30 20 10 0 10 20 30 40 power gain (db) 03692-0-004 sfdr high gain sfdr low gain oip3 high gain oip3 low gain iip3 low gain iip3 high gain nf high gain nf low gain f i gure 43. oip3, ii p3, nf , and sf dr v a riation w i th g a in a s t h e ga in in cr ea se s, th e i n p u t a m p l i t ud e r e q u ir ed t o d e li v e r t h e s a me o u t p u t a m pli t ude is r e d u ce d . this r e su l t s in less dis t o r t i o n a t t h e in p u t s t a g e , and t h er efo r e t h e o i p3 in cr e a s e s. a t s o m e p o i n t , t h e d i stor t i on of t h e i n put st age b e c o me s s m a l l en o u g h s u c h tha t t h e n o nlinea r i ty o f th e ou t p u t s t a g e becom e s do minan t . the o i p3 do es n o t i m p r o v e sig n if ic a n t l y as t h e ga i n is in cr e a s e d b e yo nd t h is p o i n t, w h ich expl a i n s t h e k n e e i n t h e o i p3 c u r v e . the iip3 c u r v e has a k n ee f o r th e s a me r e as o n ; h o w e v e r , as t h e ga in is in cr eas e d b e yo nd t h e k n e e , th e iip3 st a r ts t o de cr e a s e ra t h er t h a n i n cr e a s e . this is b e ca us e in t h is r e g i o n o i p3 is c o n s t a n t , t h er efo r e t h e hi g h er t h e ga in, t h e lo w e r th e iip3. the two ga in ra n g es ha v e eq ual s f d r a t a p p r o x ima t e l y 13 db p o w e r ga in. l a y o ut and o p er a t ing c o nsider a t io ns e a c h in p u t and o u t p u t p i n o f the ad8370 p r es en ts ei ther a 100 ? o r 50 ? im pe da n c e r e la ti v e t o th e i r r e s p ect i v e a c gr o u n d s . t o en sur e t h a t s i g n a l in t e g r i t y is n o t s e r i o u sly i m p a ir e d b y t h e p r i n t e d ci r c ui t boa r d , th e r e leva n t co nn ecti o n tra c e s s h o u ld p r o v ide an a p p r o p r i a t e cha r ac t e r i s t ic im p e danc e to the grou nd pl a n e. th i s ca n b e a c h i ev ed t h rough prope r l a yout . wh en l a y i ng o u t an rf tr ace w i th a co ntr o lled i m pe da nce, consider the following: ? space t h e ground plane to e i the r side of the sig n al tr ace at least 3 l i ne -w idt h s a w ay to e n su re tha t a micros trip (vertical di elect r ic) line is fo rm ed, rat h er t h a n a coplan ar (lateral die l ectri c ) wavegu ide. ? ensur e t h at the wid t h o f t h e mi cr o s tr ip line is c o nsta nt an d that there are as few discontinu ities as possibl e , such as com p on en t pads, alon g th e len g th of th e line. w i d t h var i a- tio n s c a use i m p e da nce disco n ti nuit ies in t h e l i ne a n d m a y result in unwanted reflection s. ? do not use s i lks c reen over t h e s i gnal li ne b e cau s e it alters the l i ne imp e d a nce. ? keep t h e le ngt h of the i n put a n d output conne c tion li nes as short as possible. f i gur e 44 shows the cross sectio n of a pc bo ard an d t a b l e 5 show the dimensions that provide a 100 ? li ne impe da nce fo r fr-4 board ma t e rial w i t h r = 4.6. table 5. 100 ? 50 ? w 22 mils 13 mils h 53 mils 8 mils t 2 mils 2 mils w 3w e r 3w h t 03692-0-021 f i g u re 44. cros s-s e c t ion a l vie w of a p c bo ar d it possible to ap proximate a 10 0 ? trace on a b o ard de sig n e d wit h the 50 ? dime ns ions abov e by removi ng t h e ground plane w i th in 3 lin e -w id t h s of t h e a r ea directly below the trac e. the ad8370 co ntains both digita l and analog s e ctions . care should b e t ake n to ensure t h a t t h e d i gi tal an d a n alog sec t ions are adequately i s olate d on t h e p c board. the us e of separate gr o u nd pla n es f o r each sect io n co nnect ed at o n ly o n e po int via a fer r i te b e a d i n ducto r ensur e s t h at the dig i t a l p u lses do no t adversely affect the analog section of the ad83 70.
ad8370 rev. 0 | page 17 of 28 due t o th e na t u r e o f th e ad837 0 s cir c ui t desig n , ca r e m u st b e ta k e n t o m i ni mize p a ras i tic ca paci ta n c e o n t h e in p u t a n d o u t p u t . the ad8370 cou l d become un sta b le wi t h m o r e tha n a f e w pf of sh un t c a p a ci t a nce o n e a ch i n p u t. u s ing r e sist o r s in s e r i es wi t h in p u t p i n s is r e c o mmende d und e r co n d i t io ns o f hig h s o ur ce ca p a c i tan c e . h i g h t r an sien t and n o i s e le ve ls o n t h e p o w e r s u p p l y , g r o u n d , and d i g i tal in p u t s ca n , un de r s o m e c i r c u m s t a n ce s , r e p r ogra m the a d 8 3 7 0 t o an u n in te n d e d ga i n co de . this f u r t her r e info r c es t h e ne e d for p r op e r su p p ly b y p a ss i n g and d e c o u p l i ng . t h e u s e r s h o u ld als o be a w a r e tha t p r ob in g th e ad8370 a nd ass o cia t ed cir c ui tr y d u r i n g cir c ui t deb u g ma y als o ind u ce th e s a me ef f e c t . p a ck a g e c o nsider a t ions the p a c k a g e o f th e ad8370 is a co m p ac t, t h er mal l y enhan c ed t ssop 16-le ad desig n . a l a rge ex p o s e d p a dd le o n t h e b o tto m of t h e d e vice p r o v ides b o t h a t h er ma l b e n e f i t and a lo w ind u c t ance p a th t o g r o u nd f o r th e cir c ui t. t o mak e p r o p er us e o f this p a c k - a g in g f e a t ur e , t h e pcb n eeds t o mak e co n t ac t dir e c t l y un der th e de vice, co n n e c te d to an ac/dc c o mm on g r o u nd r e fer e n c e wi t h as man y v i as as p o ssi b le t o lo w e r t h e i n d u c t an c e a nd t h er ma l im p e d a n c e . single-ended - t o - di fferential c o n v ersion ad8370 inhi icom v cci pw u p voc m v cco ocom ophi oplo ocom v cco ltch clck data icom inlo 67 8 23 5 1 11 10 9 15 14 16 13 12 4 serial control interface 0.1 f 1nf 0.1 f +v s c ac c ac c ac c ac r l single- ended source r s 03692-0-039 f i gure 45. sing le -ended-to - d i fferential con v e r sion the ad8370 is p r ima r il y desig n e d f o r dif f er en tial sig n al in ter - f a c i ng . t h e d e v i c e c a n b e u s e d f o r s i ng l e - e nd e d - t o - d i f f e r e n t i a l co n v ersio n sim p l y b y t e r m ina t in g th e u n us e d in p u t t o g r o u n d using a c a p a c i tor as dep i c t e d in f i g u r e 45. the ac cou p l i n g ca p a c i t o rs sh o u ld b e s e lec t ed s u c h tha t t h eir r e ac ta n c e is n e g l i- g i b l e a t t h e f r e q uen c y o f o p era t io n. f o r exa m ple , usin g 1 nf ca p a c i t o rs f o r c ac p r es en ts a ca p a ci ti v e r e ac tance o f Cj1.6 ? o n eac h in p u t n o de a t 100 m h z. this a t t e n u a t es t h e a p p l ie d in p u t v o l t a g e b y 0.003 db . i f 10 pf ca p a ci t o rs had b een s e lec t ed , t h e v o l t a g e de li v e r e d t o the in p u t wo u l d be r e d u ce d b y 2.1 db w h en o p era t in g wi t h a 200 ? s o ur ce im p e dance . differential balance (db) ?1.0 0 ?0.5 0.5 0 100 200 300 400 500 frequency (mhz) 03692- 0- 040 high gain mode (gain code hg255) low gain mode (gain code lg127) f i g u re 46. d i f f e r e nt ia l o u t p ut b a l a nc e for a single -ended input d r ive at ma xim u m g a i n (r l = 1 k?, c ac = 10 nf) f i gur e 46 il l u s t ra t e s t h e dif f er en t i al b a lan c e a t t h e o u t p ut fo r a sing le - e nde d i n p u t dr i ve fo r m u l t i p l e g a i n c o de s. the dif f er e n t i a l bala n c e i s bet t e r th a n 0.5 d b f o r si gn al f r eq ue n c ie s le s s th a n 250 mh z. f i gure 47 dep i c t s t h e dif f er en tial balan c e o v er the en t i r e ga i n ra n g e a t 10 m h z. the b a lan c e is deg r ade d fo r lo w e r ga in s e t t in gs be ca us e t h e f i ni te co mm o n ga in a l lo ws s o m e o f th e in p u t sig n al a p plied t o inhi t o p a s s dir e c t l y thr o ug h t o the o p lo p i n. a t hi g h er gai n s e t t i n g s , t h e dif f er e n t i a l gain do mina t e s a nd b a l a n c e is resto r e d . 0 0.1 0.2 0.3 0.4 0.5 0.6 diffe r e n tial balance (db) 0 96 32 64 0 3 26 49 6 1 2 8 gain code 03692-0-041 low gain mode high gain mode f i g u re 47. d i f f e r e nt ia l o u t p ut b a l a nc e at 1 0 m h z f o r a s i n g le -e nded d r ive v s . ga i n c o de ( r l = 1 k ? , c ac = 1 0 nf) e v en t h o u g h t h e a m plif ier is n o lo n g er b e in g dr i v en i n a b a l- a n c e d ma nn er , t h e dis t o r t i o n p e r f o r ma n c e r e main s ade q u a t e fo r m o st a p plic a t ion s . f i gur e 48 i l l u st ra t e s t h e ha r m o n ic dist o r t i on p e r f o r mance o f t h e circ u i t i n f i g u r e 4 5 o ver t h e e n t i re g a i n r a n g e . i f t h e am plif ier is dr i v en i n sin g le-ende d m o de, t h e i n p u t im p e dan c e va r i es dep e n d in g on t h e val u e o f t h e r e sis t o r us e d t o t e r m ina t e t h e o t h e r i n p u t as fol l o w s: rin se = rin di f f + r term w h er e r term is t h e ter m ina t io n r e sist o r co nn e c te d t o t h e o t h e r in p u t.
ad8370 rev. 0 | page 18 of 28 ?100 ?9 0 ?8 0 ?7 0 ?6 0 ?5 0 ?4 0 harm onic distortion ( d bc) 0 96 32 64 0 3 26 49 6 1 2 8 gain code 03692-0-042 hd2 hd2 low gain mode high gain mode hd3 hd3 f i gur e 4 8 . ha rm onic di stor ti on o f the ci r c ui t i n f i gur e 4 5 dc- c ouple d o p er a t io n ad8370 inhi icom vc c i pw u p voc m vc c o ocom ophi oplo ocom v cco ltch clck data icom inlo 67 8 23 5 1 11 10 9 15 14 16 13 12 4 serial control interface 1nf 1nf 0.1 f 0.1 f ?2.5v ? 2.5v 0v 0v +2.5v r l single- ended ground referenced source r s r t 03692-0-043 f i g u re 49. dc coup ling t h e a d 83 70. d u a l s u p p lies a r e us ed to s e t t h e input a n d o u tput c o mmo n-mo de le v e l s to 0 v . ad8370 ad8138 i nhi ic om vcci pwup vocm vcco oc om oph i oplo oc om vcco ltc h cl ck dat a ic om in lo 678 23 5 1 11 10 9 15 14 16 13 12 4 serial control interface 1nf 1nf 0.1 f +5v 499 ? 499 ? 100 ? 499 ? 499 ? 100 ? v oc m v ocm v ocm +5v r l single-ended ground referenced source r s r t r t 2 03692- 0- 044 f i g u re 50. dc coup ling t h e a d 83 70. t h e a d 8 1 38 is us ed as a unit y g a in leve l shi f ti ng am pli f ier to li f t the com m o n - m o d e l e v e l o f the s o urc e to m i dsup pl y . the ad8370 is als o a dc acc u ra t e va r i ab le ga in a m p l if ier . th e co mmon- m o d e dc v o l t a g e p r es e n t a t t h e out p ut p i n s is i n t e r n al l y s e t t o mids up pl y usi n g w h a t is ess e n t i a l l y a b u f f ere d r e si st iv e d i vi d e r n e tw o r k co nne c t e d b e t w e e n t h e p o si t i ve su p p ly r a i l and t h e c o m m on ( g rou n d ) pi ns . t h e i n pu t pi ns are a t a s l i g h t l y hig h er dc p o t e n t ial , typ i cal l y 250 mv t o 550 mv a b o v e t h e o u t - p u t p i ns, dep e ndin g on ga i n s e tt in g. i n a ty p i c a l sin g le-su p ply a p plic a t ion, i t is n e ce ss a r y t o ra is e t h e co m m on -mo d e r e fer e n c e lev e l o f the s o ur ce an d lo ad t o ro ug hl y mids u p p l y t o ma in tain s y mm e t ri c sw i n g a n d t o a v o i d si nki n g o r so u r c i n g s t r o n g b i a s c u r r en ts f r o m th e in p u t an d ou t p u t p i n s . i t is p o s s i b le t o us e balan c e d d u al su p p lies t o al lo w g r o u n d r e f e r e nce d s o ur ce and lo ad as i n di ca te d in f i gur e 49. by co nn e c t i n g t h e v o cm p i n a nd un us e d i n pu t to g r o u nd , t h e in p u t and o u tp u t co m m on- m o de p o ten t ials a r e f o r c e d t o vir t ual g r o u nd . this al lo ws dir e c t c o upl i ng of g r ou nd re fe re nc e d s o u r c e an d l o a d s . t h e i n it i a l dif f er en tial in p u t o f fs et is typ i ca l l y o n l y a f e w 100 v. o v e r t e m p era t ur e , t h e in p u t o f fs et co u l d b e as hig h a s a f e w t e n s o f mvs. i f p r e c is e dc acc u rac y is ne e d o ver t e m p er a t ure a n d t i me , i t ma y b e n e ces s ar y t o p e r i o d ical l y m e as ur e t h e i n p u t o f fs et and t o a p pl y t h e ne ces s a r y o p p o sin g o f fs et t o t h e u n us e d dif f er en t i al in p u t, can c e l in g t h e r e su l t i n g ou t p ut o f fs et. t o addr es s si t u a t io n s w h er e d u a l s u p p lies a r e n o t co n v e n ie n t , a s e cond o p tion is p r es en t e d in f i g u r e 5 0 . the ad8 138 dif f er en t i a l a m plif ier is us e d t o t r a n sla t e t h e co m m o n - m o d e le v e l o f t h e dr i v i n g s o ur ce to midsu p ply , w h ich a l lo ws dc a c c u r a te p e r f o r m- a n c e w i t h a g r o u n d -r efer en c e d s o ur ce w i t h ou t t h e n e e d fo r d u al s u p p lies. th e b a n d wid t h o f t h e s o l u t i o n i n f i gu r e 50 is limi t e d b y th e ga in-band w id t h p r o d uc t o f th e ad8138. the n o r m alized f r eq ue n c y r e s p o n se o f bo th i m p l e m e n ta ti o n s i s s h o w n i n f i gu r e 5 1 . ?1 0 ?8 ?6 ?4 ?2 0 2 4 6 8 10 n o r m a l ized r espon se ( d b ) 1 1 0 100 1k 10k 100k 1m 10m 100m 1g frequency (hz) 03692-0-045 ad8370 with ad8138 single +5v supply ad8370 using dual 2.5v supply f i g u re 51. no r m a l i z ed f r equenc y r e s p ons e of t h e t w o s o lut i ons in fi g u r e 4 9 a n d fi g u r e 5 0
ad8370 rev. 0 | page 19 of 28 adc interf a c ing al th o u g h the ad8370 is desig n ed t o p r o v ide a 100 ? o u t p u t s o ur ce im p e dance , th e de vice is ca p a b l e o f dr ivin g a va r i ety o f loa d s wh ile m a in ta in i n g r e aso n a b le ga i n a n d d i s t o r ti o n pe r- f o r m a n ce . a comm on a p p l ic a t io n f o r th e ad8 370 is ad c dr i v i n g in if s a m p lin g r e ce i v ers a nd b r o a d b and w i de d y na m i c ra n g e dig i t i zers. the wide ga i n ad j u s t m e n t ra ng e al lo ws t h e us e o f lo w e r r e s o l u tio n ad cs. f i gu r e 52 il l u s t ra t e s a typ i cal ad c in t e r f ace n e tw ork. ad8370 v ocm r op 100 ? c ac z s r ip 03692- 0- 046 v in v in r op c ac z s r ip r t z p z in adc f i gure 52. gen e r i c a d c inter f ac e m a n y fa ct o r s n e ed t o be co n s id er ed be f o r e d e f i ni n g co m p o n en t val u es us e d i n t h e i n t e r f ace net w o r k, s u ch as t h e desir e d f r e - q u en c y ra n g e o f o p e r a t io n , t h e in p u t sw in g, a n d in p u t im p e da n c e o f th e ad c. a c co u p lin g c a p a ci t o rs, c ac , s h o u l d b e u s e d t o b l o c k an y p o ten t ial dc o f fs ets p r es en t a t t h e ad8370 o u t p u t s, w h ich w o u l d o t h e r w is e co n s u m e t h e a v ai lab l e lo w-end ra n g e o f t h e ad c. th e c ac ca p a ci t o rs s h o u ld be la rg e e n o u g h s o tha t t h e y p r es en t ne g l ig i b le r e ac t a nce o v er t h e in t e n d e d f r e q ue n c y ra n g e o f o p era t i o n. th e v o cm p i n ma y s e r v e as a n ext e r n al re f e re nc e f o r a d c s t h at d o not i n clu d e an o n - b o a rd re f e re nc e. i n ei t h er cas e , i t is s u g g es t e d t h a t t h e v o c m p i n b e de co u p le d to g r ou nd t h rou g h a mo d e r a tely l a rge b y p a ss ing c a p a c i tor ( 1 nf to 10 nf ) to help minim i ze wid e b a nd n o is e p i ck-u p . oft e n i t is w i s e t o in c l ud e in p u t a n d o u t p u t p a rasi t i c su p p r e s s io n r e sis t o r s, r ip a nd r op . p a rasi tic s u p p r es sin g r e sis t o r s he l p t o p r ev e n t r e so n a n t e f f e ct s th a t occu r a s a r e s u l t o f i n t e rn al bo n d - w i r e in d u cta n ce , pa d t o s u b s tra t e c a pa ci ta n c e , a n d s t ra y ca p a c i tan c e o f t h e p r in t e d cir c ui t bo a r d trace a r tw o r k. i f om itte d, u n d e s i r a bl e s e tt l i ng ch ar a c te r i st i c s m a y b e o b s e r v e d . t y p i cal l y , o n l y 10 ? t o 25 ? o f ser i es r e sis t a n ce is al l tha t is n e ed ed t o h e l p d a m p e n r e s o n a n t e f f e ct s . c o n s i d e r i n g t h a t m o s t a d c s pre s e n t a rel a t i vely hi g h i n put i m p e danc e, ve r y l i t t l e s i g n a l is l o st ac ro ss t h e r ip a nd r op s e r i es r e sis t o r s. d e p e n d in g on t h e i n p u t i m p e da n c e p r es en t e d b y t h e i n p u t sys t em o f t h e a d c, i t ma y b e desira b l e t o t e r m ina t e t h e a d c in p u t do w n t o a lo w e r im p e d a nce b y usin g a t e r m ina t in g re s i stor , r t . the hig h f r eq uen c y r e s p o n s e o f t h e ad8370 e x h i b i t s gr ea t e r peaki n g w h en dri v i n g v e r y l i gh t l o a d s . i n addi t i o n , t h e t e r m ina t in g r e sis t or h e l p s t o b e t t er def i n e t h e in p u t im p e dan c e a t t h e ad c in p u t. a n y p a r t -t o-p a r t va r i a b i l i t y o f ad c i n p u t i m p e dance is r e d u ce d w h e n sh un t i n g do wn t h e ad c i n p u ts b y usin g a mo dera te t o lera n c e t e r m ina t in g r e sist or (ty p ica l ly a 1 % va l u e is accep t ab le). af ter def i nin g re as o n a b le v a l u es fo r co u p lin g c a p a ci to rs, s u p p r es sin g r e sis t o r s, a nd t h e t e r m ina t ing r e sis t o r , i t is time t o desig n t h e i n t e r m e d i a te f i l t er netw o r k. the exam ple in f i gur e 52 s u g g es ts a s e con d -o r d er lo w-p a s s f i l t er n e tw o r k co m p r i s e d o f s e r i es in d u c t o r s and a sh un t c a p a ci to r . t h e o r der a nd ty p e o f f i l t e r n e t w o r k us e d dep e n d s on t h e desir e d hig h f r e q uen c y r e j e c t io n r e q u ir e d fo r t h e ad c in t e r f ace , as w e l l as o n p a ss- b an d r i p p le a nd g r o u p del a y . i n s o me si tua t ion s , t h e si gn al s p ectra m a y alr e a d y b e s u f f i ci en tl y ba n d - li mi ted s u ch t h a t no a d d i t i on a l f i lte r ne t w or k i s ne c e ss ar y , i n w h i c h c a s e z s w o u l d sim p l y b e a sh o r t an d z p wou l d b e an op e n . i n ot he r s i tu a t i o ns , i t m a y b e ne c e ss ar y to h a ve a r a t h e r h i g h - o rd e r an t i - a l i a s i ng f i lte r to he lp m i n i m i z e u n w a n t e d h i g h f r e q u e nc y sp e c t r a f r o m b e in g a l i a s e d do w n in t o t h e f i rst n y q u ist zon e o f th e a d c. t o p r o p erl y desig n t h e f i l t er n e t w o r k, i t is n e ce ss a r y t o co n s ider t h e o vera l l s o urc e and lo ad i m p e dance p r e s e n t e d b y t h e a d 8 370 a nd a d c i n p u t, in cl u d in g t h e a ddi t i ona l r e sist ive co n t r i b u t i on o f s u p p r es sio n and t e r m ina t ing r e sis t o r s. th e f i l t er desig n c a n t h e n b e h a nd l e d b y u s i n g a s i ng l e - e nd e d e q u i v a l e n t c i rc u i t a s sho w n i n f i g u re 5 3 . a v a r i e t y of re f e re nc e s t h a t a d d r e s s f i lte r syn t h e sis a r e a v a i la b l e . m o s t p r o v ide tab l es fo r va r i o u s f i l t er t y pes a n d o r d e rs, in d i ca tin g th e n o rm al ized in d u ct o r a n d ca pa ci - t o r va l u es f o r a 1 h z cu t o f f f r eq uen c y an d 1 ? lo ad . af ter scalin g t h e n o r m ali z e d p r o t o t yp e e l e m e n t val u es b y t h e ac t u al desir e d c u t-o f f f r e q uenc y a n d lo ad i m p e dan c e, i t is si m p ly a ma t t er o f s p li t t in g s e r i es elem e n t r e ac t a n c es in half t o r e alize t h e f i nal b a l a nc e d f i lte r ne t w or k c o m p o n e n t v a lu e s . v s r s 2 r s 2 r l 2 r l 2 z s 2 z s 2 z p v s r s r l z s z p source load balanced configuration single-ended equivalent 03692-0-047 f i gure 53. sing le-ended-t o - d i f f e rent i a l net w ork co nver s i on a s an exa m ple , a s e cond-o r der bu t t er w o r t h lo w-p a s s f i l t er desig n is p r es e n t e d w h er e t h e dif f er en t i al lo ad i m p e dance is 1200 ?, a n d t h e p a dded s o ur ce im p e dan c e o f th e ad8370 is as s u m e d t o b e 1 20 ?. th e n o r m alize d s e r i es i n d u c t o r val u e fo r th e 10-t o -1 lo ad-t o-s o ur ce im p e dan c e ra tio is 0. 074h, a nd the n o r m alize d s h u n t c a p a ci t o r is 14.814 f . f o r a 70 mh z c u t o f f f r e q u e nc y , t h e s i ng l e - e nd e d e q u i v a l e n t c i rc u i t c o ns i s t s of a 200 nh s e r i es ind u c t o r f o l l o w ed b y a 27 pf ca p a ci t o r . t o r e alize th e ba lan c e d eq ui valen t , sim p l y s p li t t h e 200 nh ind u c t o r in h a l f to re a l i z e t h e ne t w or k s h ow n i n fi g u re 5 4 .
ad8370 rev. 0 | page 20 of 28 v s r s 2 r s r l r s 2 r l 2 r l 2 27pf v s r s = 120 ? r l = 1200 ? 200nh 100nh 100nh 27pf balanced configuration de-normalized single-ended equivalent v s r s = = 0.1 r l = 1 ? l n = 0.074h c n 14.814f normalized single-ended equivalent = 60 ? = 60 ? = 600 ? = 600 ? f c = 70mhz f c = 1hz 03692-0-048 f i gure 54. s e c o nd- o r d er butter wor t h l o w - p a ss f i lte r d e s i gn ex amp l e a co m p lete desig n exa m p l e is sh o w n in f i gur e 56. th e ad837 0 is co nf igur e d fo r sin g le-e n d e d -to-dif f er en t i al con v ersio n w i t h t h e i n put t e r m ina t e d dow n t o p r es e n t a s i n g l e - e nde d 75 ? i n p u t. a sixt h-o r der c h eb ysh e v dif f er en t i al f i l t er is us e d t o i n t e r f ace th e o u t p u t o f the ad8370 t o the in p u t o f th e ad9430 170 ms ps 12-b i t a d c. the f i l t er minimi zes aliasi n g ef fe c t s an d i m p r o v es h a r m on i c d i stor t i on p e r f or m a n c e. the in p u t o f t h e ad9430 is t e r m ina t e d wi th a 1.5 k? r e sis t o r s o t h a t t h e o v eral l lo ad p r es en te d to t h e f i l t er n e two r k is ~1 k? . the va r i ab le ga i n o f t h e ad837 0 ext e n d s t h e us e a b l e d y na mic r a nge of t h e a d c . t h e me a s u r e d i n te r m o d u l a t i o n d i s t or t i on of t h e com b in a t ion is p r es en t e d i n f i gur e 55 a t 4 2 mh z. ? 130 ? 120 ? 100 ?60 ?40 ?20 ?10 0 ?80 ? 110 ?70 ?50 ?30 ?90 dbfs 0 1 02 03 04 0 5 06 07 0 frequency (mhz) 03692-0-050 f i g u re 55. fft p l ot of t w o - t o ne int e r m odu l at io n d i s t o r t i on at 4 2 m h z fo r the c i rcui t i n f i gur e 56 i n f i g u re 5 5 , t h e i n t e r m o d u l a t i o n pro d u c t s are c o m p ar abl e to t h e n o is e f l o o r o f t h e a d c. the s p ur io us-f r e e d y na mic ran g e o f t h e com b i n a t ion is b e t t e r t h an 6 6 d b fo r a 70 m h z me asure m e n t b a ndwi d t h . 3 v oper a t ion i t is p o s s i b le t o o p era t e the ad8370 a t v o l t a g es as lo w as 3 v w i t h on ly m i no r p e r f or m a nc e d e g r a d a t i o n . t a bl e 6 g i ve s t y pi c a l sp e c if ic a t ion s fo r o p era t io n a t 3 v . table 6. parameter typical (70 mhz, r l = 100 ?) ouptut ip3 +23.5 dbm p 1 d b + 1 2 . 7 d b m ?3 db bandwidth 650 mhz (hg 12 7) imd3 ? 82 dbc (r l = 1 k?) ad8370 inhi icom v cci pw u p voc m v cco ocom ophi oplo ocom v cco ltch clck data icom inlo 67 8 23 5 1 11 10 9 15 14 16 13 12 4 serial control interface from 75 ? tx-line 0.1 f 1nf 0.1 f +v s 27pf 68nh 180nh 220nh 39pf 27pf 1.5k ? 68nh 180nh 220nh 25 ? 25 ? c ac c ac 100nf 100nf c ac 100nf c ac 100nf r s 120 ? 03692-0-049 v in b ad9430 v in a f i g u re 56. a d c int e r f ac e e x a m pl e
ad8370 rev. 0 | page 21 of 28 ev alua tion board and softw a re the e v al u a tion bo a r d al lo ws q u ic k t e s t in g o f the ad8370 b y usin g st anda r d 50 ? test e q u i pm e n t. t h e s c h e ma t i c is sh o w n i n f i gur e 57. t r a n s f o r m e rs t1 an d t2 a r e us ed t o tra n sf o r m 50 ? s o ur ce a nd lo ad im p e d a n c es to t h e desir e d i n p u t a nd o u t p ut r e fer e n c e le vels. the to p and b o t t om l a yers a r e sh o w n i n f i gur e 61 a nd f i gur e 62. th e g r o u n d plan e was r e m o ve d u n der t h e t r aces b e tw e e n t1 a nd pin s inhi and inlo to a p p r o x im a t e a 100 ? c h a r ac ter i s t ic im p e dance . the e v al u a tion bo a r d com e s wi th the ad8370 co n t r o l s o f t wa r e tha t al lo ws s e r i a l ga in con t r o l f r o m m o s t com p u t ers. the ev al ua ti o n boa r d i s co nn ect e d vi a a ca b l e t o th e pa rall e l po r t o f t h e com p ut er . sim p l y b y ad j u s t i n g t h e s l ider b a r in t h e co n t r o l s o f t wa r e , t h e ga in co de is a u t o ma tical l y u p da ted t o th e ad8370. 31 0 1 2 49 8 7 61 1 5 2 13 1 15 22 24 16 21 20 19 18 23 17 14 25 d-sub 25 pin male ad8370 inhi icom v cci pw u p voc m v cco ocom ophi oplo ocom v cco ltch clck data icom inlo 67 8 23 5 1 11 10 9 15 14 16 13 12 4 23 5 14 c8 0.1 f out+ out? in+ in? c7 0.1 f c6 1 f c5 0.1 f +v s v s gnd gnd p2 vocm pwup c2 c1 t1 1:4 t2 2:1 r2 0 ? r1 0 ? r3 0 ? r4 0 ? c4 c10 open r8 49.9 ? r9 open sw1 c3 1nf 1nf 1nf 1nf c9 open l2* l1* r7 1k ? r6 1k ? r5 1k ? 03692-0-051 tc4-1w 50 ? tx line 50 ? tx line 50 ? tx line 50 ? tx line jtx-2-10t * emi suppression ferrite hz1206e601r-00 f i g u re 57. a d 8 3 7 0 ev aluat i on bo ar d s c he mat i c
ad8370 rev. 0 | page 22 of 28 f i g u re 58. ev aluat i on s o f t w a r e table 7. ad83 70 evaluation board configuration options c o m p o n e n t f u n c t i o n default conditi o n vs, gnd, vocm power interface vector pins. apply supply vo ltag e between vs a n d gnd. the vocm pin allo ws e x ternal monitoring of the commo n-mo de input and output bias levels. not applica b le sw1, r8, c10, pwup device enable. set to position b to power up the device. when in position a, the pwup pin is connected to the pwup v e ctor pin. t h e pwup pin allo ws external power cycling of the device. r8 and c10 are provided to allow for proper c a ble termination. sw1 = installed r8 = 49.9 ? (size 0805) c10 = open (size 0805) p1, r5, r6, r7, c9 serial contro l in terface. the evaluation board ca n be contro lled using most pcs. wind ows? ba se d control softwa re is ship pe d with the evaluation kit. a 25-pin d-sub connector c a bl e is required to connect th e pc to the evaluation board. it may be necessary to use a capacitor on the clock li ne, depending on th e quality of the pc port signals. a 1 nf capacitor for c9 is usua lly sufficie n t for reducing clock overs h oot. p1 = installed r5, r6, r7 = 1 k? (size 0603) c9 = open (size 0603) j1, j2, j6, j7 input and outp ut signal conne ctors. t h ese sma connectors pr ovide a conve n i e nt way to interface the evaluation board with 50 ? test equipment. typically the device is evaluated using a single-end ed source and lo ad . t h e source sho u ld connect to j 1 ( i n+) , and the load sh ould connect to j6 ( o ut +) . not applica b le c1, c2, c3, c4 ac coupling capacitors. provid e ac coupling of the input and output signals. c1, c2, c3, c4 = 1 nf (size 0603) t1, t2 impedance t r an sformers. t1 provides a 50 ? to 200 ? impedance transformati on. t2 provides a 100 ? to 50 ? impe d ance transfor mation. t1 = tc4 ?1w (minicircuits) t2 = j t x?2?10t (minicircuits) r1, r2, r3, r4 single-ended or differential. r2 and r4 ar e used to ground the c e nter tap of the second ary wind ings on transf or mers t 1 and t 2 . r1 and r3 should be used to gro u nd j2 and j7 when us ed in single end e d applic ations. r1, r2, r3, r4 = 0 ? (size 0603 ) c5, c6, c7, c8 l1, l2 power supply d e coupling. nom i nal sup p ly d e co up ling consists of a ferrite bead series inductor follow e d by a 1 f capacitor to ground followed by a 0.1 f capacitor to ground position e d as clos e to the device as po ss ible. c7 prov ides additional dec o upling of the input common-mode voltage. l1 prov ides high frequen c y isolatio n between the input and output power supp ly. l2 provid es hig h frequency isolation between t h e anal og and digital ground. c6 = 1 f (size 0 805) c5, c7, c8 = 0.1 f (size 0603) l1, l2 = hz1206 e601r-00 (steward, size 1206)
ad8370 rev. 0 | page 23 of 28 03692- 0- 076 f i g u re 59. ev aluat i on b o a r d t o p si lk s c r e e n 03692-0-078 f i gure 6 0 . e v a l ua tio n bo ar d bo tto m si l k scr e en 03692-0-077 f i g u re 61. ev aluat i on b o a r d t o p 03692-0-079 f i gure 6 2 . e v a l ua tio n bo ar d bo tto m
ad8370 rev. 0 | page 24 of 28 appe ndix char a c teriz a ti on e q uip m e n t an a g i l e n t n44 41a b a lan c e d m e as ur emen t s y s t em w a s us e d t o o b ta in t h e ga in , p h a s e , gr o u p d e la y , r e v e r s e i s ola t i o n , cmrr , a nd s-p a r a m e te r info r m a t io n c o n t a i ne d i n t h is d a t a she e t. w i t h t h e excep t ion fo r t h e s-p a ram e ter info r m a t io n, t - a t t e n u a t o r pa d s w e r e u s ed t o ma t c h th e 5 0 ? im peda n c e o f th is i n s t r u m e n t s p o r t s t o th e ad8370. an a g ilen t 4795a s p ec tr um anal y z er was us e d to ob t a i n no n l i n e a r m e asu r em e n ts imd , i p 3, a nd p1db t h rou g h m a tc h i ng b a lu ns a n d / o r a t t e n u a t or ne t w or k s . v a r i ou s o t h e r m e a s ur em en t s w e r e ta k e n wi th se t u ps sh o w n in th i s secti o n . c o mposite w a veform assumption t h e n o nlin ea r tw o- t o n e m e as ur e m en t s m a d e f o r th i s d a ta sh e e t , i . e., imd and ip 3, a r e b a s e d on t h e a ssu m p t i on o f a f i xe d va l u e co m p osi t e wa v e f o r m a t the o u t p u t , g e n e ral l y 1 v p-p . th e f r e- q u en cies o f i n t e r e s t dic t a t e t h e us e o f rf t e s t e q ui pm e n t, and b e ca us e t h is e q ui pm en t is ge n e ra l l y n o t desig n e d t o w o rk in uni t s o f v o l t s, b u t ra t h er wa t t s and dbm, a n as sum p tion was ma de t o fa ci li t a te e q u i pme n t s e t u p and op er a t ion. t w o si n u s o i d a l t o n e s can b e r e pr es en t e d as v 1 = v s i n (2 f 1 t ) v 2 = v s i n (2 f 2 t ) the rms a v erag e v o l t a g e o f one t o n e is 2 1 ) ( 1 2 0 = dt v t t 1 w h er e t is t h e p e r i o d o f t h e w a vefo r m . th e rm s a v era g e v o l t a g e o f th e tw o- t o n e co m p osi t e si gn al i s 1 ) ( 1 2 0 = + dt v v t 2 t 1 i t ca n b e sh o w n t h a t t h e a v era g e p o w e r o f t h is co m p osi t e wa v e f o r m is twice (3 db) tha t o f th e sin g le t o n e . this als o m e a n s t h a t t h e com p osi t e p e ak-t o -p e a k v o l t a g e is t w ic e (6 db) t h a t o f a sin g le t o n e . thi s p r in ci ple can b e us e d t o s e t c o r r e c t in p u t a m p l i t udes f r o m g e n e ra t o rs s c aled in dbm and is co r r ec t if the t w o tone s are of e q u a l a m pl it u d e an d are re a s on ably cl o s e i n fr e q u e n c y . definitions of selec t ed p a r a me ters c o mm on- m o d e r e j e c t io n r a t i o (f igur e 26) has b e e n def i n e d fo r th i s c h a r a c t e ri za ti o n e f f o r t a s gain mode common gain mode al differenti w h er e t h e n u m e ra t o r is t h e ga in in t o a dif f er en t i al lo ad a t t h e o u t p ut d u e t o a dif f er en t i al s o ur ce a t t h e in pu t, a nd t h e den o mina t o r is t h e ga i n i n t o a dif f er en t i al- m o d e lo ad a t t h e output d u e to a c o m m on - m o d e s o u r c e a t t h e i n put . i n te r m s of mixe d- m o de s- p a r a m e ters, t h is e q u a tes to sdc21 sdd21 m o r e info r m a t io n o n m i xe d- mo de s-p a r a m e te rs ca n b e o b t a i n e d i n a re fe re nc e b y b o c k el m a n , d . e . a n d e i s e nst a dt , w. r . , c o m b i n e d d i ffer en ti a l a n d c o m m o n -m od e s c a t t e r i n g p a r a m e t e rs: theo r y a n d s i m u l a ti o n . ieee t r a n s a c t io n s o n m i cr o w a v e th e o r y a n d t e c h niq u es, v 43, n 7, 1530 ( j u l y 1995). r e v e rs e is ol a t ion (f igur e 24) is def i n e d as s d d 12. p o we r su p p ly re j e c t ion r a t i o ( p sr r ) has b e e n d e f i ne d as s dm a a w h er e a dm is t h e dif f er en t i a l mo de fo r w a r d ga in (s dd21), a nd a s is th e ga in f r o m the p o w e r su p p l y p i n s ( v c c i a nd v c c o , t a k e n t o g e t h er) t o t h e o u t p ut (o p l o an d ophi, t a k e n dif f er en - t i a l ly ), co r r e c te d fo r im p e d a nc e misma t ch. t h e fol l o w in g re f e re nc e prov i d e s more i n f o r m a t i o n : gr a y , p . r . , h u r s t , p . j . , l e wis, s.h. and m e yer , r . g., an a l y s i s a n d d e s i g n o f a n a l o g in t e g r a t e d c i r c u i t s , 4 th ed i t i o n , j o h n w i l e y & s o n s , i n c . , p a g e 4 2 2 .
ad8370 rev. 0 | page 25 of 28 ad8370 i nhi ic om v cci pwu p voc m v cco ocom ophi oplo ocom v cco ltch clck data ic om in lo 67 8 23 5 1 11 10 9 15 14 16 13 12 4 1 f 1 f t1 t2 0 ? 1nf 1nf 1nf 1nf 1nf 1nf 1nf 03692-0-064 mini- circuits tc4-1w v s 5.0v v s 5.0v v s 5.0v serial data source a g ilen t 8753d ne tw ork analy z e r mini- circuits tc2-1t ?22.5db port 1 port 2 f i g u re 63. psr r a dm te s t s e t u p ad8370 inhi icom vcci pwup vocm vcco oc om oph i oplo oc om vcco ltc h cl ck dat a icom inlo 67 8 23 5 1 11 10 9 15 14 16 13 12 4 200 ? 1nf 1nf 1nf 1nf 1nf 03692-0-066 serial data source agilent 8753d net w o rk anal yz er mini- circuits tc2-1t port 1 port 2 bias tee connection to port 1 f i g u re 64. psr r a s te s t s e t u p
ad8370 rev. 0 | page 26 of 28 ad8370 inhi icom vcci pwup vocm vcco oc om oph i oplo oc om vcco ltc h cl ck dat a icom inlo 678 23 5 1 11 10 9 15 14 16 13 12 4 1 f 50 ? input aux in tektronix tds5104 dpo oscilloscope hp8133a 3ghz pulse generator 50 ? input 50 ? input 50 ? input 475 ? 200 ? 52.3 ? 52.3 ? 475 ? 1 f 1nf 1nf 1nf 03692-0-080 v s 5.0v 2db atten 2db atten 3db atten 3db atten trig out out 6db splitter 3db atten 3db atten 6db splitter v s 5.0v v s 5.0v serial data source f i gur e 6 5 . dc p u l s e resp o n se a n d o v er dri v e reco v e r y t e st setup ad8370 inhi icom v cci pw u p voc m v cco ocom ophi oplo ocom v cco ltch clck data icom inlo 678 23 5 1 11 10 9 15 14 16 13 12 4 1 f 475 ? 475 ? 105 ? 1 f t1 t2 0 ? 1nf 1nf 1nf 1nf 1nf 1nf 1nf 03692-0-081 mini- circuits tc4-1w v s 5.0v v s 5.0v v s 5.0v serial data source mini- circuits jtx-2-10t agilent 8648d signal generator rf out 50 ? input 50 ? input tektronix tds5104 dpo oscilloscope tektronix p6205 active fet probe f i gure 66. g a in ste p t i me d o ma in res p onse t e st s e tup
ad8370 rev. 0 | page 27 of 28 ad8370 inhi icom v cci pw u p voc m v cco ocom ophi oplo ocom v cco ltch clck data icom inlo 67 8 23 5 1 11 10 9 15 14 16 13 12 4 1 f 52.3 ? 475 ? 475 ? 105 ? 1 f t1 t2 0 ? 1nf 1nf 1nf 1nf 1nf 1nf 1nf 03692-0-082 mini- circuits tc4-1w v s 5.0v v s 5.0v v s 5.0v serial data source mini- circuits jtx-2-10t agilent 8648d signal generator rf out agilent 33250a function/arbitrary waveform generator output 10mhz in 10mhz ref out 50 ? input 50 ? input tektronix tds5104 dpo oscilloscope tektronix p6205 active fet probe f i gur e 6 7 . pwup resp o n se tim e d o mai n t e st setup
ad8370 rev. 0 | page 28 of 28 outline dimensions compliant to jedec standards mo-153-abt 16 9 8 1 exposed pad (pins up) 5.10 5.00 4.90 4.50 4.40 4.30 6.40 bsc 3.00 sq top view bottom view 1.20 max 0.15 0.00 1.05 1.00 0.80 0.65 bsc 0.30 0.19 seating plane 0.20 0.09 8 0 0.75 0.60 0.45 f i g u re 68. 1 6 -l ead t ssop (r e - 16) ordering guide model temperature package descri ption package option ad8370are C40 c to +85 c 16-lead tssop, tube re-16 ad8370are- r ee l7 C40 c to +85 c 16-lead tssop, 7 reel re-16 a d 8 3 7 0 - e v a l e v a l u a t i o n boar d ? 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 . d03692-0-1/0 4(0)

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