SI8900-1 Datasheet, PDF (22/30 Pages) Silicon Laboratories – ISOLATED MONITORING ADC

Si8900/1/2
6.3. Application Example
Figure 17 shows the Si8900 operating as a single-phase ac line voltage and current monitor. The VDDA dc bias
circuit uses a low-cost 3.3 V linear regulator referenced to the neutral (white wire). The ac current is measured on
ADC input AIN0. The ac line voltage is scaled by resistors R17 and R18 and level-shifted by the 1.5 V VREF. AC
line current is measured using differential amplifier U1 connected across shunt resistor R1. Data is transferred to
the external controller or processor via the isolated UART.
Single‐Phase
AC Line
1.5 V
R2
R3
R4
R1
R5
U1
Low Cost
Dual OpAmp
R17
R7
R18
R8
R9
R10
1.5 V
C1
R12
D1
R13 ^C4
U2
3.3 V
LDO
C5
R6 _C2
R11
C3
R14
1.5 V
R15
AIN0 ^Si8900
AIN1
VDDA
GNDA
T_X
R_X
VDDB
GNDB
External
Master Controller
Output Side
Bias Supply
Figure 17. AC Line Monitor Application Example
22
Rev. 1.0