Hi,
I'm designing a precise Mains Energy Meter (Class 0.2). There's a mandatory requirement in the design spec
- .. shall detect the homopolar (Phase-Neutral) current in range (10mA ... 30mA) with 10% accuracy
In this Spice implementation I expected CMRR of the circuit should be
60dB or so ... When i compare V_Common_mode and Vout with FFT, the 5KHz is far that attenuation although the 50Hz Carrier is canceled.Don't understand, the AD8605 has a comfortable open-loop gain/bandwith, Please someone could explain me.
Version 4 SHEET 1 1956 680 WIRE -608 -288 -688 -288 WIRE -432 -288 -608 -288 WIRE -320 -288 -432 -288 WIRE -240 -288 -320 -288 WIRE -96 -288 -160 -288 WIRE 48 -288 -96 -288 WIRE 176 -288 48 -288 WIRE 304 -288 256 -288 WIRE -432 -240 -432 -288 WIRE -96 -240 -96 -288 WIRE -608 -160 -608 -288 WIRE 192 -160 192 -176 WIRE -688 -144 -688 -288 WIRE 48 -144 48 -288 WIRE 160 -144 48 -144 WIRE -432 -128 -432 -160 WIRE -432 -128 -544 -128 WIRE 304 -128 304 -288 WIRE 304 -128 224 -128 WIRE 352 -128 304 -128 WIRE -96 -112 -96 -160 WIRE -16 -112 -96 -112 WIRE 160 -112 48 -112 WIRE -432 -96 -432 -128 WIRE -96 -80 -96 -112 WIRE 192 -80 192 -96 WIRE -16 32 -16 -112 WIRE 176 32 -16 32 WIRE 224 32 224 0 WIRE -688 48 -688 -64 WIRE -608 48 -608 -80 WIRE -608 48 -688 48 WIRE -432 48 -432 -16 WIRE -432 48 -608 48 WIRE -320 48 -432 48 WIRE -256 48 -320 48 WIRE -96 48 -96 0 WIRE -96 48 -176 48 WIRE 48 48 48 -112 WIRE 48 48 -96 48 WIRE 448 64 448 -16 WIRE -544 80 -544 -128 WIRE 112 112 112 96 WIRE 176 128 176 32 WIRE 176 128 144 128 WIRE -16 144 -16 32 WIRE 80 144 -16 144 WIRE 224 160 224 112 WIRE 224 160 144 160 WIRE 112 192 112 176 WIRE 448 192 448 144 WIRE 224 208 224 160 WIRE 224 320 224 288 WIRE -544 336 -544 160 FLAG 192 -80 0 FLAG 352 -128 out FLAG 448 -16 p3v3 FLAG 224 0 p3v3 FLAG 192 -176 p3v3 FLAG 448 192 0 FLAG -16 -112 mid FLAG -320 -288 Hi FLAG -320 48 Lo FLAG -544 336 0 FLAG 112 192 0 FLAG 112 96 p3v3 FLAG 224 320 0 FLAG -432 -128 V_Common_Mode SYMBOL res 272 -304 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 330K SYMBOL res -80 16 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R2 SYMATTR Value 10K SYMBOL res -80 -144 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R3 SYMATTR Value 10K SYMBOL res 208 128 M180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R4 SYMATTR Value 10K SYMBOL res 208 304 M180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R5 SYMATTR Value 10K SYMBOL res -624 -176 R0 SYMATTR InstName R6 SYMATTR Value {Rburden} SYMBOL current -688 -64 R180 WINDOW 0 24 80 Left 2 WINDOW 3 24 0 Left 2 WINDOW 123 24 52 Left 2 WINDOW 39 0 0 Left 0 SYMATTR InstName I1 SYMATTR Value SINE(0 10u 50) SYMBOL voltage 448 48 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value 3.3 SYMBOL Opamps\\AD8505 192 -192 R0 SYMATTR InstName U1 SYMBOL res -144 -304 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 806 SYMBOL res -160 32 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R8 SYMATTR Value 806 SYMBOL res -448 -256 R0 SYMATTR InstName R9 SYMATTR Value 10k SYMBOL res -448 -112 R0 SYMATTR InstName R10 SYMATTR Value 10k SYMBOL voltage -544 64 R0 WINDOW 3 24 44 Left 2 WINDOW 123 24 124 Left 2 WINDOW 39 0 0 Left 0 SYMATTR InstName V_Common_Mode SYMATTR Value SFFM(0 1 50 0.8 5000) SYMBOL Opamps\\AD8505 112 80 M0 SYMATTR InstName U2 TEXT 360 -248 Left 2 !.tran 100m TEXT -928 -24 Left 2 !;.step param I_mes 10u 100u 10u TEXT -448 288 Left 2 !;ac dec 200 10 1meg TEXT -1016 -176 Left 2 ;I1 represent a CT 1:2000 ratio TEXT -1240 -208 Left 2 ;I1 Homopolar Current betwenn Ph and Neutral wires TEXT -992 72 Left 2 !.step param Rburden 10 50 10