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polyphase energy metering ic with pulse output ade7752 fea t ures high ac curacy , s u pport s 50 hz /6 0 h z iec 687/ 61 036 less than 0. 1% error over a dyn a mic ran g e of 5 00 to 1 compatible wit h 3-ph ase/ 3- wir e delt a an d 3-ph ase/4 - wi re wy e configurations the ad e7 752* s u pplie s average real pow e r on t h e frequency output s f1 and f2 high frequen c y output cf i s int e nde d for calibr ation an d sup p lies in stant a neou s re al p o wer logic out p ut ne gp indi cates a p o tential m i swiri n g or n e gative power for each phase direct driv e for electrome c hani cal co unters an d 2 - pha s e step p e r motors (f1 and f2) prop rietary ad cs and d s p pro v ide hi gh acc u r a cy over large variation s in en vironmental co ndition s an d ti me on-chip po wer supply monitor i ng on-chip cree p p r otection (no lo ad thr e shol d) on-chip referen c e 2. 4 v 8 % (2 0 pp m/c ty pica l ) w i th e x ternal overdriv e ca pa bility single 5 v su ppl y, low po wer (6 0 mw typical ) low co st c m o s proce ss *p ate nt pe nd ing. gener a l de scription th e ad e7752 is a hig h accurac y p o l y phas e ele c t r i c a l en erg y m e as ur em en t i c . th e p a r t s p e c if i c a t io n s s u r p as s th e accurac y r e q u ir em en ts as q u o t e d in t h e iec61036 s t a n da r d . th e o n l y a n a l o g cir c ui t r y us e d in t h e ad e7752 is i n t h e ad cs a n d r e f e r e n c e cir c ui t. a l l o t h e r signa l p r oces sin g (e.g. , m u l t i p lica t i o n , f i l t er in g, an d s u m- ma t i o n ) is car r i ed o u t in t h e dig i t a l do main. this a p p r oac h p r o v ides s u p e r i o r s t a b ili t y a n d accurac y o v er extr em es in en vir o n- me n t a l co ndi t i o ns and o v e r t i me. th e ad e7752 s u p p lies a v era g e r e a l p o wer inf o r m a t io n o n t h e lo w f r e q uen c y o u t p uts, f1 a n d f2. thes e log i c o u t p u t s ma y b e us e d to d i r ectl y d r i v e a n e l ectr o m ec h a n i c a l c o u n t e r o r t o in t e rf a c e w i th a n mcu . th e cf lo g i c o u t p u t g i v e s i n s t a n t a n e o u s r e al p o wer inf o rma- t i o n . this o u t p u t is in ten d e d to b e us e d f o r ca li b r a t io n p u r p os es. th e ad e7752 in c l udes a p o wer s u p p l y m o ni to r i n g cir c ui t o n t h e v dd p i n. th e ad e7752 wi l l r e m a i n inact i v e un t i l th e s u p p l y v o l t a g e on v dd r e ac h e s 4 v . i f t h e s u p p l y fa l l s b e lo w 4 v , t h e ad e7752 wi l l a l s o b e r e s e t a n d n o p u ls es wi l l b e is s u e d o n f1, f2, a n d cf . i n t e r n al p h ase m a t c hin g cir c ui t r y en s u r e s t h a t t h e v o l t a g e a n d cur r en t c h a n n e ls a r e p h ase ma t c he d . an in t e r n a l n o load t h r e s h o l d en s u r e s t h e p a r t does no t exhi b i t a n y cr e e p w h en th er e is n o load . th e ad e7752 is a v a i la b l e in a 24-le ad so i c p a c k a g e. func ti onal bl oc k di a g ram 7 8 15 10 14 13 5 6 16 9 lpf hpf 3 clk out clkin dgnd cf s1 f1 f2 s0 scf negp digit al- t o -fre qu ency conver te r 2.4v ref ref in/out a gnd 4k ? ibp ibn vbp vn icp icn vcp iap ian va p adc adc adc adc v dd ade7752 po wer suppl y monit or adc adc phas e correction phase correction phase correction 11 12 4 1 8 2 1 2 2 2 3 2 4 1 20 19 2 17 hpf hpf lpf lpf abs x x x 02676-a - 001 f i gur e 1 . f u nctio n al bl oc k dia g r a m 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 ? 2003 analog de vices, i n c. al l r i ght s r e ser v ed . rev. b obsolete
ade7752 table of contents s p e c if ic a t io n s ..................................................................................... 3 t i min g c h a r ac ter i s t ics ..................................................................... 4 a b s o l u t e m a xim u m r a t i n g s ............................................................ 5 t e r m in olog y ...................................................................................... 6 p i n c o nf igura t io n an d f u n c t i on d e s c r i p t ion s ............................. 7 t y p i cal p e r f o r ma n c e c h a r ac t e r i s t ics ............................................. 9 t e st cir c ui t ...................................................................................... 11 the o r y o f o p era t io n ...................................................................... 12 p o w e r f a c t o r c o n s idera t ion s .................................................... 12 n o n s in us o i dal v o l t a g e and c u r r en t ......................................... 13 analog i n p u ts .................................................................................. 14 c u r r en t c h a n ne ls ....................................................................... 14 v o l t a g e c h ann e ls ........................................................................ 14 t y p i cal c o nn e c t i o n d i a g ram s ...................................................... 15 c u r r en t c h a n ne l c o nn e c t i on ................................................... 15 v o l t a g e c h ann e ls c o nn e c t i on .................................................. 15 m e t e r c o nne c t io n s ..................................................................... 15 p o w e r s u p pl y m o ni t o r . .................................................................. 17 hp f an d of fs et ef fe c t s .............................................................. 17 dig i t a l - t o -f r e quen c y c o n v ersio n ................................................ 18 m o d e s e lecti o n o f th e s u m o f th e t h r e e a c ti v e en e r gi e s . . . . 19 p o w e r m e as ur em e n t c o n s ider a t io n s ....................................... 19 t r a n sfer f u n c t i o n ........................................................................... 20 f r e q uen c y o u t p u t s f1 an d f2 .................................................. 20 f r e q uen c y o u t p u t cf ................................................................ 21 s e le c t ing a f r e q uen c y fo r a n energ y m e t e r a p plica t ion ........... 22 f r e q uen c y o u t p u t s ..................................................................... 22 n o l o ad thr e sh old . ................................................................... 23 n e g a t i v e p o w e r i n fo r m a t io n . .................................................... 23 o u t l in e dim e n s io n s ....................................................................... 24 or der i n g g u ide . ......................................................................... 24 revision history lo c a t i o n p a g e 9/03da ta she e t c h an ge d fro m r e v . a t o re v . b p da t e d f o r m a t ................................................................................................................. .................................................................................. n iv ers a l c h a n g e t o f i gure 19 ............................................................................................................ ............................................................................................. 15 5/03da ta she e t c h an ge d fro m r e v . 0 t o r e v . a ch a n g e d f 1C5 to f 1C7 ............................................................................................................................... .............................................................. n iv ers a l c h a n g e t o f i gure 6 ............................................................................................................. .............................................................................................. 10 c h a n g e s t o f r e q uen c y o u t p u t s f1 a n d f2 s e c t io n ................................................................................. ..................................................................... 13 replace d t a b l e ii .............................................................................................................. ................................................................................................ 13 c h a n g e s t o x am ples 1, 2, a n d 3 ................................................................................................ ..................................................................................... 14 replace d t a b l e iii ............................................................................................................. ................................................................................................ 14 replace d t a b l es iv , v , a nd vi .................................................................................................. ........................................................................................ 15 c h a n g e s t o s l cting a fr nc fo r a n nr g mtr app l i c a t i o n s e c t ion ....................................................... ................ 15 c h a n g e s t o no l o ad th rs h o l d s e c t ion ........................................................................................... .................................................................. 16 replace d t a b l e vii ............................................................................................................. ............................................................................................... 16 r e v. b pa ge 2 o f 2 4 obsolete
ade7752 specifica t ions table 1. v dd = 5 v 5%, ag n d = dgn d = 0 v, on -chip re ference , clki n = 1 0 mh z, t min to t ma x = ?40c to+ 85c p a r a m e t e r c o n d i t i o n s m i n t y p m a x u n i t accuracy 1, 2 measurement error on current channe l voltage channe l with full-scale signal (500 mv), 25c, over a dynamic range of 500 to 1 0.1 % reading phase error bet w een channels pf = 0.8 capacitive 0 . 1 ( d e g r e e s ) pf = 0.5 capacitive 0 . 1 ( d e g r e e s ) ac power supply rejection scf = 0; s0 = s1 = 1 output frequency variation (cf) ia = ib = ic = 10 0 mv rms, va = vb = vc = 100 mv rms, @ 50 hz, ripple on v dd of 200 mv rms @ 100 hz 0 . 0 1 % reading dc power supply rejection s1 = 1; s0 = scf = 0 output frequency variation (cf) v1 = 100 mv rm s, v2 = 100 mv r m s, v dd = 5 v 250 mv 0.1 % reading analog in puts see analog inputs section maximum signal levels v ap ?v n , v bp ?v n , v cp ?v n , i ap ?i an , i bp ?i bn , i cp ?i cn 0.5 v peak diff. input impedance (dc) clkin = 10 mhz 370 410 k bandwidth (?3 db) clkin/256, clkin = 10 mhz 14 k h z adc offset error 1, 2 2 5 m v gain error external 2.5 v reference, ia = ib = ic = 500 mv dc 9 % ideal referenc e in p u t ref in /ou t input voltage range 2.4 v + 8% 2 . 6 v 2.4 v ? 8% 2.2 v input impedance 3 . 3 k input capacitance 1 0 p f on-chip refe r e nce nominal 2.4 v reference error 2 0 0 m v temperature coefficient 2 5 p p m / c clkin all specificati o n s for clkin of 10 mhz input clock fre quency 1 0 m h z logic inputs 3 acf, s0, s1, and abs input high volt age, v inh v dd = 5 v 5% 2.4 v input low voltage, v inl v dd = 5 v 5% 0 . 8 v input current, i in t y pically 10 na, v in = 0 v to v dd 3 a input capacitance, c in 1 0 p f logic outputs 3 f1 and f2 output high vol t age, v oh i sou r ce = 10 ma, v dd = 5 v 4.5 v output low voltage, v ol i sin k = 10 ma, v dd = 5 v 0 . 5 v cf and negp output high vol t age, v oh v dd = 5 v, i sou r ce = 5 ma 4 v output low voltage, v ol v dd = 5 v, i si n k = 5 ma 0 . 5 v power supply for specified performance v dd 5 v 5% 4.75 5 . 2 5 v i dd 1 2 1 6 m a 1 se e s e ct ion for ex p l anati o n of s p ecif ications . t e rmin ology 2 se e p l ot s i n typi . ca l pe rfo r m a n ce ch a r a c t e ri st i c s 3 sampl e tes t ed d uri ng initial rel e as e a n d a f t e r a n y re de si g n or pr oces s ch a n g e t h a t m a y a ffect t h i s pa ra m e t e r. r e v. b | pa ge 3 o f 2 4 obsolete
ade7752 timing characteristics table 2. v dd = 5 v 5%, agn d = dgn d = 0 v, on -chip re ference , clki n = 1 0 mh z, t min to t ma x = ?40c to + 85c 1, 2 p a r a m e t e r c o n d i t i o n s u n i t t 1 3 275 f1 and f2 pulse width (logic hi gh) ms t 2 see table 6 output pulse pe riod. see transfer function sect ion. sec t 3 1 / 2 t 2 time between f1 falling edge and f2 falling edge sec t 4 3, 4 96 cf pulse width ( l ogic high) ms t 5 5 see table 7 cf pulse period. see transfer function sectio n. sec t 6 clkin/4 minimum time between f1 and f2 pulse sec 1 sampl e tes t ed d uri ng initial rel e as e a n d a f t e r a n y re de si g n or pr oces s ch a n g e t h a t m a y a ffect t h i s pa ra m e t e r. 2 se e . f i g u r e 2 f i g u re 2. ti ming d i ag r a m f o r f r equen c y o u t p ut s 3 the pulse widths o f f1, f2, and cf are not fixed for higher output fr eque ncie s. s e e fre s e ctio n. q ue ncy outputs f r eq uen c y out p ut s 4 cf i s n o t syn c h r on ous t o f1 or f2 freq uen c y out p ut s. 5 th e c f pu lse i s a l w a ys 1 s i n t h e h i gh freq uen c y m o de . s e e s e ct i o n . f1 f2 cf t 1 t 6 t 2 t 3 t 4 t 5 02676-a - 003 r e v. b pa ge 4 o f 2 4 obsolete
ade7752 absolute maximum ra tings table 3. t a = 2 5 c, u n les s ot herwi s e not e d p a r a m e t e r r a t i n g v dd to agnd ?0.3 v to +7 v v dd to dgnd ?0.3 v to +7 v analog input voltage to agnd vap, vbp, vcp, v n , iap, i a n, ibp, i b n, icp, and icn ?6 v to +6 v reference input voltage to agn d ?0.3 v to v dd + 0.3 v digital input voltage to dgnd ?0.3 v to v dd + 0.3 v digital output v o ltage to dgnd ?0.3 v to v dd + 0.3 v operating tem p erature range industrial ?40c to +85c storage temperature range C65c to +150c unction tempe r ature 150c 24-lead soic, p o wer dissipation 88 mw ? a thermal impedance 250c/w lead temperature, soldering vapor phase (60 sec) 215c infrared (15 sec) 220c 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 r a t i ng o n 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 a n y o t h e r con d i t io ns a b o v e t h os e list e d i n t h e o p era t io nal s e c t io n s o f t h is sp e c if ic a t io n is n o t i m pli e d . e x p o sur e t o a b s o l u t e max i m u m ra t i ng co ndi t i on s fo r ex ten d e d p e r i o d s ma y a f fe c t de vice r e l i ab i l i t y . esd caution esd (electrostatic discharge) sensitive device. ele c tros tatic charg e s as high as 4000 v readily accumulate on the human body and test eq uipment and can discharge wi thout detection. although this product features proprietary esd protection circu i try, permanent dama ge may occur on devices subjected to high energy electrostatic discharges. theref ore, prop er esd precautions a r e recommended to avoid perform a nce degradation or l o ss of functiona l ity. r e v. b | pa ge 5 o f 2 4 obsolete
ade7752 rev. b | page 6 of 24 terminology measurement error the error associated with the energy measurement made by the ade7752 is defined by the following formula: % energy true energy true C ade by registered energy error percentage 100 7752 ? ? ? ? ? ? = error between channels the hpf (high-pass filter) in the current channel has a phase lead response. to offset this phase response and equalize the phase response between channels, a phase correction network is also placed in the current channel. the phase correction net- work ensures a phase match between the current channels and voltage channels to within 0.1 over a range of 45 hz to 65 hz and 0.2 over a range of 40 hz to 1 khz. see figure 25 and figure 26. power supply rejection this quantifies the ade7752 measurement error as a percentage of reading when the power supplies are varied. for the ac psr measurement, a reading at a nominal supply (5 v) is taken. a 200 mv rms/100 hz signal is then introduced onto the supply and a second reading is obtained under the same input signal levels. any error introduced is expressed as a percentage of reading. see definition for measurement error. for the dc psr measurement, a reading at nominal supplies (5 v) is taken. the supply is then varied 5% and a second reading is obtained with the same input signal levels. any error introduced is again expressed as a percentage of reading. adc offset error this refers to the dc offset associated with the analog inputs to the adcs. it means that with the analog inputs connected to agnd, the adcs still see an analog input signal offset. however, as the hpf is always present, the offset is removed from the current channel and the power calculation is not affected by this offset. gain error the gain error of the ade7752 is defined as the difference between the measured output frequency (minus the offset) and the ideal output frequency. the difference is expressed as a percentage of the ideal frequency. the ideal frequency is obtained from the ade7752 transfer function. see the transfer function section. obsolete
ade7752 pin conf igura t ion and fu nction descriptions top view (not to scale) ade7752 ref in/out agnd icn icp ibn cf dgnd v dd negp ibp ian iap vn vcp vbp vap abs s0 f2 s1 f1 scf clkin clkout 2 3 4 5 6 7 8 9 10 11 12 12 4 23 22 21 20 19 18 17 16 15 14 13 02676-a - 003 f i gure 3. pin config ur ation ta ble 4. pi n f u nct i on d e s c ri pt i o ns pin no. mnemonic description 1 c f calibrati o n frequency logic output. the cf logic outp ut gives instantaneou s re al power inform ation. this output is intend ed to be used fo r calibrat ion pur pose s . see the scf pin descripti o n. 2 d g n d this provides the ground reference for the digital circuitr y in the ade7752, i.e., multiplier, filters, and digital-to- frequency conv erter. because the digital return currents in the ade7752 are small, it is acceptable to connect this pin to the a n alog ground pl ane of the who l e system. 3 v dd power supply. this pin pr ovides the supply voltage for the digita l circuitry in the ade7752. the s u pply voltage should be maint a ined at 5 v 5% for specified operatio n . t h is pin shou ld be d e coupled to dgnd with a 10 f capacitor i n par a lle l with a 100 nf ceramic capacitor. 4 n e g p t h is logic output will go logic h i gh when negati ve power is detected on any of th e three phase inputs, i.e., when the ph ase angle betwee n the voltage and the curre nt signals is gre a ter than 90. this output is not latched and wil l be reset when p o sitive po wer is on ce agai n d e t e c t e d . s e e t h e section. 5, 6 7, 8 9, 10 iap, ian ibp, ibn icp, icn analog inputs for current channel. this cha nne l is intended for use wi th the current transducer and is referenced in this document as the current channel. these in puts are fully differential vo ltage in puts with maximum differential input sign al leve ls of 0.5 v. see th e analog inputs section. bo th inputs have internal esd protection circu i try in addition, an overv o ltage of 6 v can be s u stained on thes e inputs without risk of permane n t damage. 1 1 a g n d this pin prov ides the ground reference for the analog circuitry in the ade7752, i.e., adcs, temperature sensor, and reference. this pin should be ti ed to the analog ground plan e or th e quietest ground reference in the system. t h is quiet ground reference should be u s ed for all an alo g circuitry, e.g., antialia sing filte r s, current and voltage transducers, and so on. to keep ground no ise ar ound the ade7752 to a minimum, the quiet ground plane should on ly connect to the digital ground plane at one po int. it is accepta b le to place the entire device on the anal og ground plane. 1 2 r e f in /ou t this pin prov ides access to the o n -chip vo ltage r e ference. the o n -chip refere nc e has a nom i nal value of 2.4 v 8% and a typical temperature coefficient of 20 ppm/ c. an external reference source may also b e connected at this pin. in eithe r case, this pi n s h ould be decoupled to agnd with a 1 f ceramic capac i tor. 13C16 vn, vcp, vbp, vap analog inputs for the voltage channel. this cha nnel is intended for use with the voltage transducer and is referenced in this document as the voltage ch an nel. these in puts are single-end ed voltage inputs with a maximum signa l level of 0.5 v with respect to vn for specified operatio n . all in puts have intern al esd protection circu i try in addition, an overv o ltage of 6 v can be s u stained on thes e inputs without risk of permane n t damage. 17 abs this logic input is used to select the way the three active energie s from the three phase s are sum m ed. this offers the designer the capabilit y to do th e arith m etical sum of the three energi es (abs logic high) or the sum of the abso lute values (abs logic low) . s e e t h e s e c t i o n . 1 8 s c f select calibr ation frequency. this logic in put is used to select the freq uency on the calibration output cf. table 7 show s how th e calibr ation fre q uencies ar e sel e cted . 1 9 c l k i n master clock for adcs and digit a l sign al proc es sing. an externa l cloc k can be pr ovided at this logic input. alternatively, a parallel re son a n t at cr ystal can be conne cted across cl kin and clkout to provide a clock source for the ade7752. the clock frequency for specifie d oper a tion is 10 mhz. ceramic load capacitors of between 22 pf and 33 pf shoul d be used with the gate osci llator circuit. refer to the crystal manufacturers data sheet for load c a pacitan c e requ irements. n e g a t i v e p o w e r i n f o r m a t i o n m o d e selection of the s u m of the three a c t i v e e n e r g i e s r e v. b pa ge 7 o f 2 4 obsolete
ade7752 pin no mneoni desription 2 c l o u t a rystal an e onnete aro ss this pin an clin as esrie preiously to proie a l o soure or the ade7752 the c l out pin an rie one cmos loa when an e ternal lo i s supplie at clin or when a rystal is eing use 2 22 s s these logi in puts are use to selet one o our possile re uenies or the igital-to-reuen y onersio n this oers the esigner greater le iility when esigning the energy e t e r s e e t h e s e tion 2 2 f f2 low freueny logi outputs f an f2 supply aerage re al power inoration the logi outputs an e use to rie eletro ehani al o unters an 2-pha s e stepper o tors iretly see the transer funtion setion s e l e t i n g a f r e u e n y o r an energy mete r a p p l i a t i o n r e b pa ge o 2 obsolete
ade7752 typical perf orm ance cha r acte ristics current channel o full sale 5 5 2 2 e rror o re a ing wye connection on-chip reference phase c phase b phase a b c p h a s e a 27-a - f i g u re e r r o r as a p e r ent o r e a ing with intern al ree ren e w ye conn e t i on 2 2 wye connection on-chip reference 25 c pf 5 2 5 c p f c p f 5 5 c pf 5 current channel o full sale e rror o re a ing 27-a - 5 f i g u re 5 e r r o r as a p e r ent o r e a ing o er p o wer f a t o r with intern al ree ren e w ye conn e t i on current channel o full sale 5 5 2 2 e rror o re a ing wye connection external reference 25 c pf 5 2 5 c p f c p f 5 5 c pf 5 27-a - f i g u re e r r o r as a p e r ent o r e a ing o er p o wer f a t o r with e te rn al re e ren e w ye conn e t i on 2 2 wye connection on-chip reference 25 c pf 5 c pf c p f current channel o full sale e rror o re a ing 27-a - 7 f i g u re 7 e r r o r as a p e r ent o r e a ing o er t e pe r at u r e with intern al ree ren e w ye conn e t i on 5 5 2 2 delta connection on-chip reference pf pf 5 p f 5 current channel o full sale e rror o re a ing 27-a - f i g u re e r r o r as a p e r ent o r e a ing o er p o wer f a t o r wi th internal reeren e d el ta c o nneti o n 5 2 5 2 wye connection external reference 2 5 c p f c p f 5 c pf current channel o full sale e rror o re a ing 27-a - f i g u re e r r o r as a p e r ent o r e a ing o er t e pe r at u r e with e te rn al re e ren e w ye conn e t i on r e b pa ge o 2 obsolete
ade7752 5 55 5 frequency h 5 5 5 2 2 p f 5 pf wye connection on-chip reference e rror o re a ing 27-a - f i g u re e rror as a p e r e n t o r e a in g o er f r euen y wi th a n internal reer e n e w y e co nneti on 5 5 2 2 wye connection external reference 5 v 5 2 5 v 75v current channel o full sale e rror o re a ing 27-a - f i gure e rror as a p e r e n t o r e a in g o er p o wer sup p l y with e te rn al re e ren e w ye conn e t i on 2 5 5 5 chi pha offset v 2 5 2 5 n mean 5 sd 2 min 27 max 25 range 52 27-a - 2 f i g u re 2 cha nne l o s et d i s t r i ut i o n 5 5 2 2 current channel o full sale e rror o re a ing wye connection on-chip reference 5 v 5 2 5 v 75v 27-a - f i gure e rror as a p e r e n t o r e a in g o er p o wer sup p l y with intern al ree ren e w ye conn e t i on re b page o 2 obsolete
ade7752 test circuit v dd abs ref inout nf nf nf 25 p f v dd vn ag nd dgnd f 7 f2 cf clout clin s s scf mh 22pf 22pf ps25- 7 ade7752 v dd 2 2 to freq counter 2 iap ian ibp ibn icp icn rb same as iap ian same as iap ian not connected same as vap negp nf p f vap vbp vcp nf m 22v nf i same as vap 5 7 5 2 22 2 2 load 27-a - f i gure t e st c i r uit or p e r or a ne cur es re b page o 2 obsolete
ade7752 rev. b | page 12 of 24 theory of operation the six voltage signals from the current and voltage transducers are digitized with adcs. these adcs are 16-bit second order -? with an oversampling rate of 833 khz. this analog input structure greatly simplifies transducer interface by providing a wide dynamic range for direct connection to the transducer and also simplifying the antialiasing filter design. a high-pass filter in the current channel removes the dc component from the current signal. this eliminates any inaccuracies in the real power calculation due to offsets in the voltage or current signalssee hpf and offset effects section. the real power calculation is derived from the instantaneous power signal. the instantaneous power signal is generated by a direct multiplication of the current and voltage signals of each phase. in order to extract the real power component (i.e., the dc component), the instantaneous power signal is low-pass filtered on each phase. figure 15 illustrates the instantaneous real power signal and shows how the real power information can be extracted by low-pass filtering the instantaneous power signal. this method is used to extract the real power information on each phase of the polyphase system. the total real power information is then obtained by adding the individual phase real power. this scheme correctly calculates real power for nonsinusoidal current and voltage waveforms at all power factors. all signal processing is carried out in the digital domain for superior stability over temperature and time. the low frequency output of the ade7752 is generated by accumulating the total real power information. this low frequency inherently means a long accumulation time between output pulses. the output frequency is therefore proportional to the average real power. this average real power information can, in turn, be accumulated (e.g., by a counter) to generate real energy information. because of its high output frequency and therefore shorter integration time, the cf output is proportional to the instantaneous real power. this pulse is useful for system calibration purposes that would take place under steady load conditions. power factor considerations the method used to extract the real power information from the individual instantaneous power signal (i.e., by low-pass filtering) is still valid when the voltage and current signals of each phase are not in phase. figure 16 displays the unity power factor condition and a dpf (displacement power factor) = 0.5, i.e., current signal lagging the voltage by 60, for one phase of the polyphase. if we assume the voltage and current waveforms are sinusoidal, the real power componen of the instantaneous power signal (i.e., the dc term) is given by: () ? ? ? ? ? ? 60 cos 2 1 v time iap ian va p hpf lpf ibp ibn vbp icp icn vcp vn digital-to- frequency digital-to- frequency f1 f2 cf instantaneous real power signal instantaneous power signal - p(t) instantaneous total power signal va ia + vb ib + vc ic 2 abs |x| lpf lpf |x| |x| p(t) = i(t) v(t) where: v i 2 {1+ cos (2 t)} v(t) = v cos ( t) i(t) = i cos ( t) p(t) = v i 2 v i v i 2 multiplier multiplier multiplier hpf hpf adc adc adc adc adc adc 02676-a-015 figure 15. signal processing block diagram obsolete
ade7752 this is t h e co r r e c t r e a l p o w e r ca lc u l a t io n. inst ant aneous real po wer signal inst ant aneous po wer signal v u i 2 u cos(60 q ) v u i 2 inst ant aneous po wer signal inst ant aneous real po wer signal 60 q current current v o lta g e 0v 0v v o lta g e 02676-a - 016 f i g u re 16. dc com p onent of ins t a n t a neous p o wer s i g n a l convey s r e al p o we r inf o rm at i o n pf < 1 os is o i d a l vol t a e ad cr r et t h e r e al po w e r calcula t i o n m e t h o d also h o ld s t r ue f o r n o n s i n - us o i dal c u r r en t a nd v o l t a g e w a vefo r m s. a l l v o l t a g e and c u r r en t wa v e fo r m s in prac t i ca l a pplic a t io n s w i l l ha ve s o m e h a r m o n ic co n t e n t. s in g t h e f o ur ier t r a n sfo r m, in st a n t a n e o u s v o l t a g e a nd c u r r en t w a v e fo r m s ca n b e exp r es s e d i n t e r m s o f t h eir ha r m o n ic con t e n t n n n o t n v v t v d u u f sin w er e v t i s t e i n s t a n ta n e o u s v o l t a g e v o is t e a v er a g e val u e v n is t e r m s va l u e o f v o l t a g e a r m o n ic n a nd n is t e pas e a n g l e o f t e v o l t a g e a r m o n ic n n n o t n i v i t i e u u f sin w er e i t is t e in st a n t a ne o u s c u r r en t i o i s t e d c co m p o n en t i n is t e r m s value o f c u rr en t ar m o n ic n n is t e pas e an g l e o f t e c u r r en t a r m o n ic s in g e q u a tio n s a nd , t e r e al p o w e r , p , ca n b e ep r es s e d i n t e r m s o f i t s f u ndam e n t al r e al p o w e r p and a r m on i c re a l po w e r p h p p p h w er e cos e d i i u i v p n n n n n n h n i v p e d i i u f cos a s c a n b e s e e n f rom e q u a t i on , a a r m on i c re a l p o we r c o m p o n e n t is ge n e r a t e d fo r e v er y a rm o n i c , p r o v ide d t a t a r m o n ic is p r es en t i n b o t t e v o l t a g e and c u r r en t wa v e fo r m s t e p o w e r fac t o r calc u l a t ion as been s o w n t o b e acc u ra t e in t e cas e o f a pu re s i n u s o i d t e r e f ore, t e a r m on i c re a l p o we r m u st a l s o co r r ec tl y acco u n t f o r p o w e r fac t o r sin c e i t is made u p o f a s e r i es o f p u r e sin u s o ids n o t e ta t t e in p u t band wid t o f t e a n alog in p u ts is kh z wi t a mas t er c l o c k f r eq uen c y of h z rev b page of obsolete
ade7752 analog inputs current channels the o l t a g e o u t p u t s r o t h e u r r en t t r a n s u ers a r e o nne t e t o th e ad e7752 u r r en t h a nnels whi h a r e u l l y i er en tial o l t a g e i n p u ts i a p ibp an ic p a r e t h e p o si t i e in p u ts o r i a n ibn an i c n r e sp e t i ely the ai u p e a i er en t i a l sig n al o n t h e u r r en t ha nne l s h o u l e les s tha n 5 v 5 v r s o r a p u r e sin u s o ial sig n al o r t h e sp e i ie op era t io n differential input r 5v max pea 5v a gnd v cm ia iap v cm 5 v common-mode r 25v max ian iap ian 27-a - 7 f i g u re 17. m a x i mu m s i g n a l l e vels, cu rr e n t cha nne l f i gur e 17 i l l u st r a tes t h e max i m u m sig n a l le vels o n i a p and i a . th e maxi m u m dif f er en t i al v o l t a g e b e tw e e n i a p and i a is 500 mv . th e dif f er en tial v o l t a g e sig n al on the in p u ts m u st b e r e f e r e n c e d t o a c o m m o n m o d e , e . g . , a d . t h e m a x i m u m co mm o n -mo d e sig n al s h own in f i gur e 17 is 25 mv . v o l t a e ch aels the o u t p u t o f t h e li ne v o l t a g e t r a n s d ucer is conn e c t e d t o t h e ad e7752 a t this a n alog in p u t. v o l t a g e c h anne l s a r e a ps eudo- dif f er en t i al v o lt a g e i n p u t. v a p , vbp , an d v c p ar e t h e p o si t i v e in p u ts wi t h r e s p e c t t o v. the maxi m u m p e ak dif f er en t i a l sig n al o n t h e vol t a g e chann e l i s 500 mv (353 mv r m s f o r a p u r e sin u s o idal sig n al) f o r sp e c if ie d o p er a t io n. f i gur e 1 8 f i g u re 18. m a x i mu m s i g n a l l e vels, v o lt ag e c h an nel i l l u st r a tes t h e max i m u m sig n a l le vels t h a t c a n b e co nnec t e d t o t h e ad e7752 s v o l t a g e c h ann e ls. differetial ipt r 500mv ma pea 500mv a d vc m va va p v cm 500m v commo-mode r 25mv ma v va p v 02676-a - 018 v o l t a g e channel s m u st b e dr i v e n f r o m a co m m o n - m o d e vol t a g e, i . e . , t h e dif f er en t i al v o l t a g e sig n a l o n t h e in p u t m u s t b e re f e re nc e d to a c o m m on mo d e ( u su a l ly a d ) . t h e an a l o g in p u ts o f th e ad e7752 ca n be dr i v en wi t h comm on-mo d e v o l t a g es o f u p to 25 mv wi th res p ec t t o a d . h o w e v e r , best r e su l t s a r e achi e v e d usin g a com m on m o de e q u a l to a d . rev. b page 14 of 24 obsolete
ade7752 typical connecti on diagrams current chan nel c o nnec t i o n f i g u re 1 9 f i gure 19. t y pic a l conne c t ion for c u r r ent channe ls show s a t y pi c a l c o n n e c t i on d i ag r a m f o r t h e c u r r e n t c h a n n e l (i a ) . a c t (curr e n t tra n s f o r m e r) i s th e curr e n t tra n s - d u ce r se lect ed fo r th i s e x a m p l e . n o ti ce t h e co mm o n -m ode vol t a g e fo r t h e c u r r en t cha nnel i s a g n d an d is der i ve d b y cen t er t a p p in g t h e b u r d en r e sis t o r t o a g nd . this p r o v ides t h e c o m p l e me n t ar y an a l o g i n put s i g n a l s for i a p an d i a n . t h e c t tu r n s r a t i o a n d bu rd e n re s i stor r b are s e l e c t e d to g i ve a p e a k dif f er en tial v o l t a g e o f 500 mv a t maxim u m lo ad . iap r 500mv r b rf rf ct neutral phase ip ian cf cf 02676- a - 019 v o l t a g e ch annels c o nnec t i o n f i g u r e 2 0 f i g u re 20. t y pic a l conne c t io ns f o r v o lt ag e ch ann e ls s h o w s t w o t y p i cal co nn ecti o n s f o r th e v o l t a g e c h a n n e l. t h e f i r s t opt i o n u s e s a p t ( p ot e n t i a l t r ans f or me r ) to prov i d e co m p let e is ola t io n f r o m the main v o l t a g e . i n t h e s e con d op tio n , th e ad e7752 is b i as e d a r o u n d t h e n e u t ral wir e , a nd a r e sis t o r d i v i d e r i s u s e d t o prov i d e a vo lt age s i g n a l prop or t i on a l to t h e lin e v o l t a g e . a d j u s t in g the ra tio o f r a , rb , an d vr is als o a co n v enien t wa y o f ca r r yin g o u t a ga in calib r a t ion o n t h e m e t e r . r 500mv ra rb vr va p a gnd rf rf pt neutral phas e vn cf cf va p rf neutral phas e vn cf cf ra >> rf + vr ; rb + vr = rf 02676-a - 018 r 500mv me ter c o n n ec tio n s i n 3-phas e s e r v i c e , tw o ma i n p o w e r dis t r i b u t i o n s e r v ices exis t: 3 - ph a s e 4 - w i re or 3 - ph a s e 3 - w i re. t h e a d d i t i on a l w i re i n t h e 3-phas e 4 - wir e a r ra n g em e n t is t h e n e u t ral wir e . th e v o lt a g e lin e s ha v e a p h as e dif f er en c e o f 120 (2/3 radian s) b e tween ea c h o t h e r . s e e eq ua ti o n 5. s u u s u u u u 3 4 cos 2 3 2 cos 2 cos 2 t v t v t v t v t v t v l c c l b b l a a ( 5 ) w h er e v a , v b , a n d v c r e p r es en t t h e v o l t a g e r m s val u es o f t h e dif f er en t phas es . the c u r r en t in pu ts a r e r e p r es en t e d b y e q u a t i on 6: i s u i s u i u c l c c b l b b a l a a t i t i t i t i t i t i 3 4 cos 2 3 2 cos 2 cos 2 ( 6 ) w h er e i a , i b , a n d i c r e p r es en t t h e r m s val u e o f t h e c u r r en t o f e a ch phas e an d ? a , ? b , a n d ? c r e p r es en t t h e phas e dif f er en c e o f t h e c u r r en t and v o l t a g e chann e l o f e a ch phas e . t h e i n s t a n ta n e o u s po w e r s c a n th en be c a l c ula t e d a s f o ll o w s : p a ( t ) = v a ( t ) i a ( t ) p b ( t ) = v b ( t ) i b ( t ) p c ( t ) = v c ( t ) i c ( t ) then: i s u u i u u i s u u i u u i u u i u u c l c c c c c c b l b b b b b b a l a a a a a a t i v i v t p t i v i v t p t i v i v t p 3 8 2 cos cos 3 4 2 cos cos 2 cos cos (7) a s sh o w n in e q ua tion 7, in t h e ad e7752, th e real p o w e r calc u- la ti o n pe r p h ase i s m a d e w h en c u rr e n t a n d v o l t a g e i n p u t s o f o n e phas e a r e co nne c t e d t o t h e s a me cha n n e l (a, b , o r c). th e n t h e su m m a t i on of e a ch i n d i v i du a l re a l p o we r c a l c u l a t i o n g i ve s t h e t o t a l r e a l p o w e r info r m a t io n, p ( t ) = p a ( t ) + p b ( t ) + p c ( t ). rev. b | page 15 of 24 obsolete
ade7752 f i g u re 2 1 f i g u re 21. 3- p h as e 3- wire m e ter co nn ec t i o n w i t h a d e 7 7 52 show s t h e c o n n e c t i on s of t h e a d e 7 7 5 2 s an a l o g in p u ts wi t h t h e p o w e r lin e s i n a 3-phas e 3 - w i r e d e l t a s e r v ic e . ct rb* a n tialiasing f i lters iap ian source rb* ra* rb * vr * rf cf cf vn ra* vr * cf l oad phase a phase b phase c ct rb* va p vbp a n tialiasing f i lters ibn ibp * ra rf + vr; * rb + vr = rf 02676-a - 021 n o t e t h a t only t w o c u r r en t in p u ts an d tw o v o l t ag e in p u ts o f t h e ad e7752 a r e us ed in this c a s e . the r e al p o w e r calc u l a t ed b y t h e ad e7752 do es n o t dep e nd o n t h e s e lec t e d c h anne ls. f i g u re 2 2 show s t h e c o n n e c t i on s of t h e a d e 7 7 5 2 s an a l o g in p u ts wi t h t h e p o w e r lin e s i n a 3-phas e 4 - w i r e w y e s e r v ic e . s ource icp icn l oad ct ibp ibn a n tialiasing f i lters p hase a p hase b p hase c rb * ra* vr* cf vap ct rb * a n tialiasing f i lters iap ian ct rb* a n tialiasing f i lters rb* ra* vr* cf vcp rf cf vn rb* ra* vr* cf vbp rb* * ra rf + vr; * rb + vr = rf 02676-a - 022 f i g u re 22. 3- p h as e 4- wire m e ter co nn ec t i o n w i t h a d e 7 7 52 rev. b | page 16 of 24 obsolete
ade7752 powe r suppl y monitor the ad e7752 c o n t a i n s an o n -chi p p o w e r s u p p ly m o ni t o r . the po w e r s u p p l y ( v dd ) is co n t in uo usly m o ni t o r e d b y t h e ad e77 52. i f th e s u p p l y is les s tha n 4 v 5 % , th e ou t p u t s of th e ad e7752 wi l l b e in ac t i v e . this is us ef u l t o en sur e co r r e c t de vice st a r t u p a t p o we r - up a n d p o we r - d o w n . t h e p o we r supply mon i tor h a s b u i l t - i n h y st er esis a n d f i l t er ing. this g i v e s a hig h deg r e e o f imm u ni ty t o fals e t r ig g e r i n g d u e t o n o isy su p p l i es. a s c a n be s e en f r o m f , th e tr ig g e r leve l is n o minal l y s et a t 4 v . the t o lera n c e o n t h is t r ig g e r le v e l is ab o u t 5%. th e p o w e r s u p p l y a n d deco u p lin g f o r th e p a r t sh o u ld be s u c h tha t th e ri p p le a t v dd do es n o t exce e d 5 v 5% as sp e c if ie d fo r nor m a l op e r a t i o n . i gur e 2 3 f i gure 23. o n - c hip p o w e r su p p ly m o ni tor v dd 5v 4v 0v itera l reset iactive time active iactive 02676-a - 023 hpf a d o f fse t ef fec t s f i g u re 2 4 show s t h e e f f e c t of of f s e t s on t h e re a l p o we r c a l c u l a - t i o n . a s can b e s e en, a n o f fs et on t h e c u r r en t cha nne l and volt age chan nel c o n t r i b u te a dc c o m p one n t af te r m u lt i p l i c a t i on. s i n c e th i s d c co m p o n en t i s e x tra c t e d b y t h e l p f a n d i s use d t o g e n e r a t e t h e r e a l p o w e r info r m a t io n fo r e a ch phas e , t h e o f fs ets w i l l h a ve c o n t r i b u te d a c o nst a n t e r ror to t h e tot a l re a l p o we r ca lc u l a t ion. thi s p r ob lem is e a s i ly a v o i de d b y t h e h p f in t h e c u r r en t cha nne ls. b y r e m o vin g t h e o f fs et f r o m a t le as t on e ch an nel, no e r ror c o m p o n e n t c a n b e ge ne r a te d a t d c b y t h e m u lt ipl i c a t i on . e r ror te r m s a t c o s ( t ) are re move d by t h e l p f a n d t h e dig i t a l - to-f r e q u en c y co n v ersio n . s e e t h e dig i t a l-t o - fr e q u e n c y c o n v e r s i o n s e c t i o n . t i v t v i t i v i v i v i t i v t v os os os os os os u u u u u u u cos cos cos cos cos v os u i os i os u v v os u i dc coponent incdin err or ter is etr a c ted b the pf for rea po er caca t ion fre enc rads v u i a f i g u re 24. e f f e c t of chann e l o f f s et on t h e r e al p o wer cal c ulat ion the hp f i n t h e c u r r en t cha nne ls ha v e an ass o c i a t e d phas e re sp ons e t h a t i s c o m p e n s a te d f o r on - c h i p . f i g u re 2 5 an d f s h o w t h e phas e er r o r b etw e e n cha n ne ls w i t h t h e com- p e n s a t io n n e two r k. th e ad e7 752 is p h as e com p en s a t e d u p to 1 kh z as sh own. this en s u r e s cor r e c t ac t i v e ha r m o n ic p o w e r calcula t i o n ev en a t lo w po w e r fa ct o r s . i g u re 2 6 f i g u re 2 6 . ph a s e e r ro r b e t w e e n c h a n n e l s ( 4 0 h z to 7 0 h z ) fre ec (hz) 0.07 0.06 0.01 0 1000 200 400 600 800 ph a se ( d egrees) 0.03 0.02 0.01 0 0.05 0.04 100 300 500 700 900 02676-a - 025 f i g u re 25. phas e e r r o r bet w ee n ch ann e ls (0 h z t o 1 k h z) fre ec (hz) 0.010 0.008 0.004 40 70 45 50 ph a se ( d egrees) 0.002 0 0.002 0.006 0.004 55 60 65 02676-a - 026 rev. b page 17 of 24 obsolete
ade7752 digit a l-to-fre quency conversion a s p r eio us l y es r i e a t e r u l t i p lia t i o n t h e ig i tal o u t p u t o t h e lo w-p a s s i l t er o n t ain s t h e r e al p o w e r ino r a t io n o ea h p h a s e h o w e e r s i n e th i s l p f i s n o t a n i eal ri w a ll i l t e r i p l e en ta ti o n th e o u t p u t s i gn al also o n t a i n s a t t e n ua t e o p on e n ts a t t h e li ne r e uen y a n i t s ha r onis i e osht wher e h 2 the a g n i t ue r e s p o n s e o t h e i l t er is g i e n y 2 h w h er e t h e b u t o r e ue n y o t h e lo w- p a s s i l t er is h f o r a lin e r e u e n y o 5 h t h is w o u l g i e an a t t e n u a t io n o th e 2 h o p on en t o a p p r o ia t e l y 22 b th e o- ina t i n g ha r oni wi l l e t w ie t h e li ne r e uen y i e os2t u e t o t h e ins t an t a n e o u s p o w e r sig n al f s h o w s t h e i n st a n t a n e ou s re a l p o we r s i g n a l a t t h e output o t h e c f w h i h st i l l o n t a i n s a s i g n i ian t a o u n t o in st a n t a n e o u s p o w e r ino r - a t i o n i e o s 2 f i g u r e 2 7 . r e a l p o w e r- to - f re q u e n c y c o nv e r s i o n this sig n al is t h en p a s s ed t o t h e dig i tal - t o -f r e q u en c y co n v er t e r w h er e i t is in teg ra t e d (acc um u l a t e d ) o v er t i me to p r o d uce a n o u t p u t f r eq uen c y . this acc u m u l a tio n o f t h e sig n al wil l su p p r es s o r a v era g e o u t an y n o n-dc co m p o n e n t in t h e i n s t a n t a n e o u s r e al p o w e r sig n al. th e a v era g e val u e o f a sin u s o i d al sig n al is zer o . t h us , th e f r eq ue n c y g e n e ra t e d b y th e a d e7752 i s p r o p o r ti o n al t o t h e a v era g e re al p o w e r . f s h o w s t h e dig i t a l-t o - f r eq ue n c y co n v e r s i o n f o r s t ea d y lo ad co n d i t ion s , i . e . , co ns tan t v o l t a g e and c u r r en t. a s c a n b e s e en i n t h e dia g ram, t h e f r e q ue n c y o u t p u t cf va r i es o v e r ti m e , ev en un d e r s t ea d y loa d co n d i t i o n s . th i s f r eq ue n c y va r i a t ion is p r i m a r i l y d u e t o t h e cos(2t) co m p o n e n ts in t h e i n st a n t a n e ou s re a l p o we r s i g n a l . t h e output f r e q u e nc y on c f ca n be u p t o 160 tim e s hig h er t h a n t h e f r eq uenc y o n f1 a n d f2 . t h e h i g h e r output f r e q u e nc y i s ge ne r a te d b y a c c u m u l a t i ng t h e in s t an t a ne o u s r e al p o w e r sig n al o v er a m u c h sho r t e r t i m e , w h il e co n v e r ti n g i t t o a f r eq ue n c y . t h is s h o r t e r a c cum u la ti o n pe ri od m e an s les s a v era g in g o f t h e cos ( 2t) co m p on e n t. a s a con s e - q u e n ce , so m e o f th i s i n s t a n ta n e o u s po w e r s i gn al pa s s e s th r o u g h t h e dig i t a l-t o -f re q u en c y con v ersio n . this wi l l no t b e a p r ob le m in t h e a p plic a t ion. w h er e cf is us e d fo r ca lib r a t io n p u r p os es, th e f r eq uen c y s h o u ld be a v e r a g ed b y th e f r eq ue n c y co un t e r . this wil l r e m o v e a n y r i p p le . i f cf is bein g us e d t o m e as ur e e n e r g y , e . g., in a m i cr o p r o ce s s o r ba se d a p p l ica t io n , th e c f o u t p ut sh o u ld a l s o b e a v er a g e d t o calc u l a te p o wer . b e ca us e t h e o u t p u t s f1 a n d f2 o p era t e a t a m u c h lo w e r f r eq uen c y , m u ch m o r e a v era g in g o f t h e ins t an t a ne o u s r e al p o w e r sig n al is ca r r i e d o u t . th e r e s u l t is a gr ea tl y a t t e n u a t ed s i n u so id al co n t en t a n d a vir t uall y r i p p le-f r e e f r eq uen c y o u t p u t . lpf to etract real power ( d c term) 6 6 mltiplier lpf mltiplier lpf mltiplier lpf 6 diital-to - freec diital-to - freec f1 f2 cf va ia vb ib vc ic fre e c cf fre e c time f1 cos( 2 t) atteated b lpf 2 freec rads 2 v u i 0 istataeos real power sial (freec domai) abs time 02676-a - 027 rev. b page 18 of 24 obsolete
ade7752 mode sele c t ion of the sum of the three a c tive ene r gies the ad e7752 c a n be co nf igur e d t o exec u t e t h e a r i t hm et ic s u m o f t h e t h r e e ac t i v e en erg i es, w h = w h a + w h b + w h c , o r t h e s u m o f t h e a b s o l u t e val u e o f t h e s e e n erg i es, w h = |w h a | + |w h b | + |w h c | th e s e le c t ion b e tw e e n t h e t w o m o des ca n b e m a d e b y set t i n g th e abs p i n . logi c h i gh a n d l o gi c l o w a p p l i e d on t h e abs p i n co r r es p o n d t o t h e a r i t hm et ic s u m and t h e s u m of ab s o lute v a lu e s , re s p e c t i vel y . w h en t h e s u m o f t h e a b s o l u t e val u es is s e le c t e d , t h e ac t i v e en erg y f r o m e a ch phas e is alwa y s co un t e d p o si t i v e in t h e t o t a l ac t i v e e n erg y . i t is p a r t ic u l a r ly us ef u l in 3-ph as e 4-wir e in st a l la - t i o n w h er e t h e s i g n o f t h e ac t i v e p o w e r s h o u ld a l wa ys b e t h e s a me . i f t h e m e ter is mis c o n n e c t e d t o t h e p o w e r lin e s, i . e., ct co nne c t e d i n t h e wr o n g dir e c t i o n, t h e t o t a l ac t i v e en erg y r e co r d ed w i t h o u t th i s so l u ti o n ca n be r e d u ce d b y t w o- th i r d s . t h e s u m o f th e a b so l u t e val u e s a s s u r e s th a t th e a c ti v e en e r g y r e co r d e d r e p r es en ts t h e ac t u a l ac t i v e e n erg y de li v e r e d . i n t h is m o de , t h e r e v e rs e p o w e r p i n s t i l l det e c t s w h en n e g a t i ve p o w e r is p r es en t on an y o f t h e t h r e e phas e in p u ts. po wer measurement c o nsider a t ions c a l c u l at i n g a n d d i s p l a y i n g p o w e r i n f o r m at i o n w i l l a l w a y s h a v e s o m e a s s o c i at e d r i p p l e t h at w i l l d e p e n d o n t h e i n t e g r at i o n p e r i o d us e d in t h e m c u t o det e r m in e a v era g e p o w e r as w e l l as t h e lo ad . f o r exa m ple , a t lig h t lo ads, t h e o u t p u t f r e q uen c y ma y be 10 h z . w i t h a n in t e g r a t io n p e r i o d o f 2 s e co nds, o n l y a b o u t 20 p u ls es wi l l b e co un t e d . th e p o s s i b i l i t y o f mis s in g on e p u ls e al wa ys exis ts since th e ad e7752 o u t p u t f r eq uenc y is r u nnin g asy n c h r o n o us l y t o th e m c u tim e r . this w o u l d r e s u l t in a 1 - in- 20 o r 5% er r o r i n t h e p o w e r m e as ur emen t. rev. b | page 19 of 24 obsolete
ade7752 transfer function frequenc y output s f1 and f2 the ad e7752 c a lc u l a t es t h e p r o d uc t o f six v o l t a g e sig n als (o n c u r r en t cha nne l a n d v o l t a g e channe l) an d t h e n lo w-p a s s f i l t ers t h is p r o d uc t t o ext r ac t r e a l p o w e r info r m a t io n. this r e a l p o w e r info r m a t io n is t h e n con v er t e d to a f r e q uen c y . th e f r e q ue n c y inf o r m a t io n is o u t p u t o n f1 and f2 in the f o r m o f ac ti v e hig h p u ls es. th e p u ls e ra t e a t t h es e ou t p uts is r e l a t i ve ly lo w , e . g., 29.32 h z maxim u m f o r ac sig n als wi t h scf 1 s0 s1 1. (s ee t a b l e 6.) th i s m e a n s tha t t h e f r eq uen c y a t th e s e o u t p u t s i s g e n e r a t e d f r o m r e al po w e r in f o rm a t io n accum u la ted o v er a r e la t i v e l y lo n g p e r i o d o f time . th e r e s u l t is a n o u t p u t f r eq uen c y t h a t is p r o p o r t i o n al t o t h e a v er a g e r e al p o w e r . the a v er a g in g of t h e r e a l p o w e r sig n a l is im plic i t t o t h e dig i t a l-t o -f r e q u en c y c o n v e r s i on . t h e output f r e q u e n c y or pu l s e r a te i s rel a te d to t h e in p u t v o l t a g e si g n als b y t h e fol l o w in g e q u a t i o n : 2 7 1 922 . 5 ref c cn b bn a an v f i v i v i v freq u u u u u w er e fr e q ou t p u t f r eq ue n c y o n f a n d f h z v an, v bn , and v cn dif f er en t i al r m s v o l t a g e sig n al o n v o l t a g e can nel s v ol ts i a , i b , and i c d i f f er en t i al r m s vol t a g e sig n al on c u r r en t can nel s v ol ts v ref t e r e f e r e n c e v o l t a g e v % v o l ts f C on e o f s e v e n p o ssib le f r e q uen c ies s e le c t e d b y usin g t e log i c in p u ts scf , s, a n d s s e e t a b l e table f C frequency selection scf s1 s0 f 1C7 (hz) 0 0 0 1 . 2 7 1 0 0 1 . 1 9 0 0 1 5 . 0 9 1 0 1 4 . 7 7 0 1 0 1 9 . 0 7 1 1 0 1 9 . 0 7 0 1 1 7 6 . 2 9 1 1 1 0 . 6 0 1 f 1C 7 i s a fra c t i on o f t h e m a s t e r cl ock a n d t h e re for e wi l l va r y i f t h e speci f i e d c l kin f r equency is al tered . exampl e 1 h us if f u l l s cal e if f er en tial c o l t a es o f m a r e a p p l ie t o a c a a n c r e s p ec t i e l y m is t h e maxi m u m if f er en t i al o l t a e t h a t ca n b e c o nn e c t e t o c u r r en t a n o l t a e cha n ne ls t h e exp e c t e o u t p u t f r e uen c y is calc u l a t e as f o l l o w s f C hz , scf s s v an v bn v cn ia ib ic mv dc v rm s o f dc dc v ref v n o min a l re f e re n c e v a lu e n o t e ta t if t e o n c i p r e f e r e nce is us ed , ac t u a l o u t p u t f r e q u en cies ma y v a r y f r o m de vice t o de vice d u e to r e fer e n c e tol e r a nc e of % hz freq u u u u exampl e 2 n this exam p l e wi t h ac o l t a es o f m p e a a p p l ie t o t h e o l t a e channe ls an c u r r en t cha n ne ls t h e exp e c t e ou t p u t f r e uen c y is calc u l a t e as f o l l o w s value reference nominal v v vrms ac peak mv ic ib ia v v v s s scf hz f ref cn bn an , n o t e ta t if t e o n c i p r e f e r e nce is us ed , ac t u a l o u t p u t f r e q u en cies ma y va r y f r o m de vice t o de vice d u e to r e f e r e n c e tol e r a nc e of % hz freq u u u u u u a s c a n b e s e en f r o m t es e tw o e a m ple calc u l a t i o n s , t e maim u m o u t p u t f r eq uen c y f o r ac in p u ts is al wa ys alf o f ta t fo r dc in p u t sig n a l s t e m a i m u m f r e q ue n c y a l s o dep e nds on t e n u m b er o f p as es co nn ec ted t o t e ad e i n a p as e w i r e d e lt a s e r v ice, t e ma i m u m o u tp u t f r e q uen c y is dif f er en t f r o m t e maim u m ou t p ut f r e q uen c y in a pas e w i r e y e s e r v ice t e r e as on i s t a t t er e a r e o n ly tw o pas es co nnec t e d t o t e a n alog in p u ts, b u t als o ta t in a de l t a s e r v ice , t e c u r r en t canne l i n p u t and v o l t a g e cann e l in p u t o f t e s a m e pas e a r e n o t i n pas e i n n o r m al o p era t ion exampl e 3 n this exam p l e th e ad e2 is co nnec t e t o a 3p h as e 3 wir e d e l t a s e r ic e as s h own i n h e t o t a l r e al en er y calc u l a t ion p r o c es s e in t h e ade2 ca n be ex p r es s e as i ur e 2 1 to t a l r e a l p o w e r v a C v c i a v b C v c i b er e v a , v b , a nd v c r e p r es en t t e v o l t a g e on pas e a, b , a nd c , re sp e c t i vely i a a nd i b r e p r es e n t t e c u r r en t on pas e a and b , re sp e c t i vely rev b page of obsolete
ade7752 a s t h e v o l t a g e and c u r r en t in puts r e s p e c t e q ua t i o n s 5 an d 6, t h e tot a l re a l p o we r ( p is s u u u s u u s u u u u u s u u u u u cos cos cos cos cos cos t i t v v t v t i t v t v p ibn ibp vc vb ian iap vc va p l b l c l b l a l c l a f o r sim p lif i ca tio n , w e ass u m e t a t a b c a n d v a v b v c v t e p r eced in g eq ua ti o n be co m e s s u s u s u u u u s u s u u u cos sin sin cos sin sin t t i v t t i v p l l b l l a p t e n beco m e s s s u u s s u u sin sin sin sin t i vbn t i van p l b l a w er e va n v sin an d vb n v sin a s t e p f on e a c ca n ne l e l i m ina t es t e b bn a an i v i v p i f f u l l s cale ac vol t a g e o f mv p e ak is a p p l ied t o t e v o l t a g e ca n n e ls an d c u r r en t ca n n e ls, t e ep e c t e d o u t p u t f r e q uen c y is calc u l a t e d as fol l o w s value reference nominal v v ic v rms v ac peak v m ic ib ia v v s s scf h z f ref cn bn an , n o t e ta t if t e o n c i p r e f e r e nce is us ed , ac t u a l o u t p u t f r e q u en cies ma y v a r y f r o m de vice t o de vice d u e to r e fer e n c e tol e r a nc e of % hz freq u u u u u u u t a b l e tab l e aimum out p ut frequen c y on f an d f s o w s a co m p let e lis t in g o f al l maim u m o u t p u t f r e q u en cies w en usin g al l t r e e ca n n e l i n p u ts s c f s 1 s 0 max frequency for ac inputs ( hz) max frequency for dc inputs ( hz) 0 0 0 0 . 4 9 0.98 1 0 0 0 . 4 6 0.91 0 0 1 1 . 9 5 3.91 1 0 1 1 . 8 3 3.67 0 1 0 7 . 3 3 14.66 1 1 0 7 . 3 3 14.66 0 1 1 2 9 . 3 2 58.65 1 1 1 0 . 2 3 0.46 frequenc y output cf the p u ls e o u t p u t cf (calib ra t i o n f r e q uen c y) is in t e nde d fo r us e d u r i n g cal i b r a t io n. th e o u t p u t p u ls e ra t e o n cf ca n be u p t o 160 tim e s t h e p u ls e ra t e o n f1 a n d f2. th e lo w e r th e f 1C7 fr e - q u e n c y se lec t ed , th e hi gh e r th e c f scali n g . s h o w s h o w th e t w o f r eq ue n c i e s a r e r e la t e d , d e pen d i n g o n th e s t a t e s o f th e log i c in p u ts s0, s1, a n d s c f . b e ca us e o f i t s r e l a t i v e l y hig h p u ls e ra t e , t h e f r eq uen c y a t th i s logi c o u t p u t i s p r o p o r ti o n al t o th e i n s t a n ta n e o u s r e al po w e r . a s i s th e ca se wi th f1 a n d f2, th e fr e q u e n c y i s d e r i v e d fr o m th e o u t p u t o f t h e l o w - p a s s fi l t e r a f t e r m u l t i p lica t i o n . h o w e v e r , be ca u s e the o u t p u t f r eq uen c y is hig h , t h is r e a l p o w e r info r m a t io n is a c c u m u l a t e d o v er a m u ch sh o r t e r ti m e . t h us , le s s a v e r a g in g i s ca r r i e d o u t in th e di gi tal-t o - f r e q uen c y co n v ersio n . w i t h m u c h les s a v er a g ing o f t h e r e al p o w e r sig n al , t h e cf o u t p u t is m u c h m o r e r e sp o n si v e t o p o w e r f l uc t u a t ion s . s e e f i gur e 15. t a b l e 7 table 7. maximum out p ut frequency on c f s c f s 1 s 0 f 1C7 (hz) cf max fo r ac signals (hz) 0 0 0 1.27 160 f1, f2 78.19 1 0 0 1.19 8 f1, f2 3.66 0 0 1 5.09 160 f1, f2 312.77 1 0 1 4.77 16 f1, f2 29.32 0 1 0 19.07 16 f1, f2 117.3 1 1 0 19.07 8 f1, f2 58.65 0 1 1 76.29 8 f1, f2 234.59 1 1 1 0.60 16 f1, f2 3.67 rev. b page 21 of 24 obsolete
ade7752 selecting a frequency for an energy meter applica t ion a s sh o w n i n t h e us er a n s e le t on e o s e e n r e uen- ies this r e uen y s e le t ion e t e r in e s t h e ai u r e uen y o n f a n f2 th es e o u t p uts a r e i n t e n e t o e us e t o r i e t h e e n e r g y r e g i s t er e le t r o e hanial o r o t h e r sin e o n l y se e n i er e n t o u t p u t r e ue n i e s a n e s e let e th e a a i la l e r e uen y se leti o n h a s een o p ti i e o r a - p h a s e -wir e s e r ie wi t h a e t e r on s tan t o i pw hr an a ai u u r r en t o etween a an a t s h o w s th e o u t p u t r e ue n y o r se e ral a i u urr e n t s i max wi t h a lin e o l t a g e o 22 v p has e neu t ral i n al l as e s th e e ter o n s tan t is i pw hr t a l e 5 a l e tale v f a n f2 freueny at i p w hr t a l e i ma x (a) f1 and f 2 (hz) 1 0 0 . 1 0 2 5 0 . 2 5 4 0 0 . 4 0 6 0 0 . 6 0 8 0 0 . 8 0 1 0 0 1 . 0 0 the f 1C7 f r eq uen c ies al lo w co m p let e co v e ra g e o f this ra n g e o f o u t p u t f r e q uen c ies o n f1 an d f 2 . w h e n desig n in g a n e n erg y m e t e r , t h e n o mi nal desig n v o l t ag e o n t h e v o l t a g e cha n n e ls s h o u ld b e s e t t o half s c ale t o al lo w f o r cali b r a t io n o f th e m e t e r co n s t a n t . t h e c u r r en t cha nnel sh o u ld a l s o b e no m o r e t h a n h a l f s c ale w h e n t h e m e t e r s e es maxi m u m lo ad . this wi l l al lo w o v er c u r r en t sig n als a n d sig n als wi t h hig h cr es t fac t o r s t o be a c c o m m o d a t e d . s h ow s t h e output f r e q u e nc y on f 1 a n d f2 wh en all si x a n alog i n p u ts a r e h a lf scale . t a bl e 9 table 9. f1 a n d f2 frequency with half-scale ac in puts a b l e 9 t a b l e 9 t a b l e 9 s c f s 1 s 0 f 1C7 frequenc y o n f 1 and f 2 (half-scal e a c i n puts) 0 0 0 1 . 2 7 0.24 1 0 0 1 . 1 9 0.23 0 0 1 5 . 0 9 0.98 1 0 1 4 . 7 7 0.92 0 1 0 1 9 . 0 7 3.67 1 1 0 1 9 . 0 7 3.67 0 1 1 7 6 . 2 9 14.66 1 1 1 0 . 6 0 0.11 w h en s e lec t in g a s u i t a b le f 1C7 f r eq uen c y f o r a m e t e r d e sign , t h e fr e q u e n c y o u t p u t a t i max (maxim um lo ad) wi t h a 100 im p/kw hr m e t e r co n s t a n t s h o u ld b e co m p a r ed wi t h c o l u mn 5 o f t the f r e q uen c y t h a t is clos es t i n wi l l det e r m in e t h e b e st choi c e of f r e q u e nc y ( f 1C7 ) . f o r ex am pl e, i f a 3 - p h as e 4 - w i re w y e m e ter w i t h a 25 a max i m u m c u r r en t is b e i n g d e sig n e d , t h e o u t p u t f r eq uen c y o n f1 a n d f2 wi t h a 100 im p / kw hr m eter co n s tan t is 0.25 h z a t 25 a an d 220 v (f r o m ) . l o okin g a t , th e c l os es t f r eq uen c y t o 0.25 h z in c o l u mn 5 is 0.24 h z . ther efo r e , f 1C7 1.27 h z is s e le c t ed f o r this desig n . frequenc y output s f i gur e 2 s h o w s a t i min g dia g ra m fo r t h e va r i ous f r e q uen c y o u t p uts. th e o u t p u t s f1 and f2 a r e t h e lo w f r e q uen c y o u t p u t s th a t ca n be use d t o d i r e ctl y d r i v e a s t ep pe r m o t o r o r e l ectr o- m e cha n ic al i m pu ls e co un t e r . the f1 a n d f2 o u t p u t s p r o v ide tw o al t e r n a t in g hig h g o i n g p u ls es. th e p u ls e w i d t h (t 1 ) is set a t 275 m s , a n d t h e time b e tween t h e r i sin g e d g e s o f f1 a n d f2 (t 3 ) is a p p r o x ima t e l y half th e p e r i o d o f f1 (t 2 ). i f , h o w e v e r , th e p e r i o d o f f1 a n d f2 fal l s be lo w 550 m s (1.81 h z ), th e p u ls e wid t h o f f1 an d f2 is s e t t o half o f th eir p e r i o d . the maxim u m output f r e q u e nc i e s for f 1 and f 2 are show n i n . t a bl e 6 the hig h f r eq uen c y cf o u t p u t is in t e nded t o b e us ed f o r co m- m u nic a t i on s and ca l i b r a t ion p u r p o s es. cf p r o d uces a 96 m s - wid e ac t i v e hig h p u ls e (t 4 ) a t a f r e q u e nc y prop or t i on a l to a c t i ve p o w e r . th e cf o u t p ut f r e q uen c ies a r e g i v e n i n t a b l e 7. a s in t h e cas e o f f1 an d f 2 , if th e p e r i o d o f cf (t 5 ) fal l s be lo w 192 m s , the cf p u ls e wi d t h is s et t o half t h e p e r i o d . f o r exa m ple , if t h e cf f r e q uen c y is 20 h z , t h e cf p u ls e wi d t h is 25 m s . on e excep t io n t o this is w h en t h e m o de is s0 1, scf s1 0. i n this c a s e , t h e cf p u ls e wi d t h is 66% o f t h e p e r i o d . rev. b page 22 of 24 obsolete
ade7752 no l o a d t h reshold the ad e7752 a l s o in l ues n o lo a thr e s h ol an s t a r t-u p u r - r e n t e a t ur es t h a t e l iina t e an y r e e p e e t s in t h e e t e r the ad e7752 is esig n e t o is s u e a ini u ou t p u t r e uen y a n y loa g e n e ra ti n g a r e uen y lo w e r th a n th i s i n i u r e - u en y wi l l n o t a us e a p u ls e t o e iss u e on f f2 o r cf th e ini u ou t p u t r e uen y is g i e n as 5 o th e u l l -s ale o u t p u t r e ue n y o r ea h o th e f 7 r e u e n y s e l e t i o ns or a p p r o ia t e l y 2 o th e f 7 r e ue n y s ee f o r ea p l e o r a n en erg y e ter wi t h a i pw hr e t e r o n s tan t usin g f 7 77 h th e in i u o u t p u t r e uen y a t f o r f2 w o u l e 5 5 h this w o u l e h a t cf f h i n this ea p l e the n o lo a thr e sh o l w o u l e e ui alen t t o w o lo a o r a s t a r t-u p u r r en t o 75 a a t 2 v t a l e tab l e 10. cf, f1, and f2 min i mum frequen c y at no load threshold scf s1 s0 f1, f2 min m hz cf min mhz 0 0 0 2.44 10 C5 3.91 10 C3 1 0 0 2.29 10 C5 1.83 10 C4 0 0 1 9.77 10 C5 1.56 10 C2 1 0 1 9.16 10 C5 1.47 10 C3 0 1 0 3.67 10 C4 5.86 10 C3 1 1 0 3.67 10 C4 2.93 10 C3 0 1 1 1.47 10 C3 1.17 10 C2 1 1 1 1.15 10 C5 1.83 10 C4 nga ti v p o wr info rma t ion the ad 7752 det e c t s when t h e c u r r en t a n d v o l t a g e c h a n ne ls o f a n y o f t h e t h r e e phas e i n p u ts ha v e a phas e dif f er en c e g r e a t e r t h a n 9 0 , i . e . , a or b or c 90. this m e chan ism can dete c t w r o n g co nn ectio n o f th e m e t e r o r g e n e ra ti o n o f a c ti v e en e r g y . the ngp p i n o u t p u t wil l g o ac ti v e hig h w h en n e g a ti ve p o w e r i s d e t e ct e d o n a n y o f th e th r e e p h a s e in p u ts . i f pos i ti v e a c ti v e en erg y is det e c t e d o n al l t h e t h r e e phas es, n g p p i n o u t p ut is lo w . th e ngp p i n o u t p ut cha n g e s s t a t e a t t h e s a me t i m e as a p u ls e is is s u e d on cf . i f s e v e ral phas es m e as ur e n e g a t i ve p o w e r , th e ngp p i n o u t p u t wil l s t a y hig h un t i l al l the p h as es m e as ur e p o si t i v e p o w e r . i f a p h as e has go n e b e lo w t h e n o l o ad t h r e sh old , n g p det e c t ion o n t h is phas e is dis a b l e d . n gp det e c t ion o n t h i s phas e r e s u m e s w h en t h e p o w e r r e t u r n s o u t o f n o lo ad condi t ion. s e e t h e n o l o ad thr e sh old s e c t io n. rev. b page 23 of 24 obsolete
ade7752 outline dimensions controlling dimensions are in millimeters inch dimensions in parentheses are rounded-off millimeter equivalents for reference only and are not appropriate for use in design compliant to edec standards ms-ad 75 25 25 u 5 27 5 57 2 7 seating plane 5 2 2 25 25 25 27 5 bsc 2 2 5 7 7 22 7 2 5 2 52 5 coplanarit y f i gure 2 2-l ea stanar s all o u t line p a age s oi c w i e boy r w - 2 di e nsio ns sho w n i n i ll i e t e r s a n i n he s ordering guide moel paage desri ption paage option a d e 7 7 5 2 a r s o i c p a a g e rw-2 ADE7752ARRL soic paage rw-2 on reels eval-ade77 52e b ade7752 ealuation boar 1 rw = small out l ine wide bod y pa cka g e i n tube s 2003 analo g de vices, inc. all rights reserve d . tra d em arks and registered tra d emar ks are the proper ty o f th eir respectiv e c o mpan ies . c02676C0 C 9/03(b) rev. b | page 24 of 24 obsolete

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