CN0185: Analog-to-Analog Isolator Using AD7400A, ADuM5000, and Active Filter
Low-cost analog-to-analog isolator circuit offering 2500V rms isolation with 0.05% linearity using the AD7400A modulator and ADuM5000 isoPower DC-to-DC converter.
Overview
The CN0185 is a reference design for a complete analog-to-analog isolator providing 2500V rms isolation. It features the AD7400A second-order sigma-delta modulator, which produces an isolated 1-bit data stream. The analog signal is recovered via an ADG849 switch and a fourth-order Chebyshev active filter using the AD8646 dual op-amp. The isolated side is powered by the ADuM5000 DC-to-DC converter, enabling operation from a single 5V to 12V system supply via an ADP3301 regulator. The circuit achieves 0.05% linearity and 100 kHz bandwidth, providing a high-performance alternative to optoisolator-based systems.
Use Cases
- Motor control
- Shunt current monitoring
- Isolated voltage monitoring
- Optoisolator replacement
Topics
Referenced Parts
Analog Devices
The 5 V supply for the circuit in Figure 1 is supplied from an ADP3301 5 V linear regulator
Analog Devices
The ADP1720 or ADP7102 linear regulator can be used as a substitute for the ADP3301, if desired.
Analog Devices
The ADP1720 or ADP7102 linear regulator can be used as a substitute for the ADP3301, if desired.
Analog Devices
If the ADuM6000 is used instead of the ADuM5000, the entire circuit is rated to 5 kV.
| 33250A | Agilent | A function generator, Agilent 33250A |
| 3458A | Agilent | A digital multimeter, Agilent 3458A, 8.5 digits |
| AD7400A | Analog Devices | AD7400A Isolated Sigma-Delta Modulator |
| AD8646 | Analog Devices | AD8646 Dual, 24 MHz, Rail-to-Rail, I/O Op Amp |
| ADG849 | Analog Devices | ADG849 3 V/5 V CMOS 0.5 Ω SPDT/2:1 Mux in SC70 |
| ADP121-3.3 | Analog Devices | the V DD2 digital supply is 3.3 V supplied by the ADP121 linear regulator. |
| ADP3301-5 | Analog Devices | The 5 V supply for the circuit in Figure 1 is supplied from an ADP3301 5 V linear regulator |
| ADR443 | Analog Devices | ADR443 Ultralow Noise, LDO XFET® 3.0 V Voltage Reference |
| ADuM5000 | Analog Devices | ADuM5000 Isolated DC-to-DC Converter |
| 4396B | Agilent | A spectrum analyzer, Agilent 4396B |
| ADP1720 | Analog Devices | The ADP1720 or ADP7102 linear regulator can be used as a substitute for the ADP3301, if desired. |
| ADP7102 | Analog Devices | The ADP1720 or ADP7102 linear regulator can be used as a substitute for the ADP3301, if desired. |
| ADuM6000 | Analog Devices | If the ADuM6000 is used instead of the ADuM5000, the entire circuit is rated to 5 kV. |
| 5700A | Fluke | A multifunction calibrator (dc source), Fluke 5700A |