Broadcom

AV02-3564EN

13

ACPL-C87AT/ACPL-C87BT Data Sheet

Automotive High Precision DC Voltage Isolation Sensor

Application Information

The circuit shown in the Figure 28 is a high voltage sensing application using ACPL-C87AT/BT (isolation amplifier) and

ACPL-M49T (optocoupler). The high voltage input is sensed by the precision voltage divider resistors R1 and sensing

resistor R2. The ratio of the voltage divider is determined by the allowable input range of the isolation amplifier (0 to 2 V).

This small analog input goes through a 39Ω and 10 nF anti aliasing filter (ACPL-C87AT/BT use

- modulation).

Inside the isolation amplifier: the analog input signal is digitized and optically transmitted to the output side of the amplifier.

The detector will then decode the signal and converted back to analog signal. The output differential signals of

ACPL-C87AT/BT go through an op-amp to convert the differential signals to a single ended output.

Figure 28: Typical Application Circuit for Battery Voltage Sensing

Bypass Capacitor

Figure 29: Bypass Capacitors C2, C4

V+

V-

R1

R2

R3 39

C2

0.1 F

R12

R13

R5 20 k

R4 20 k

R7 20 k

0.1 F

VOUT

Vref

M

C

U

ACPL-C87AT/BT

ACPL-M49T

R6 20 k

C1

10 nF

C4

0.1 F

C6

1 nF

C7 1 nF

20

SWITCH

MODE

POWER

SUPPLY

Battery Cells

10 k

ACPL-C87AT/BT

C4

0.1 F

C2

0.1 F