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This version (13 Sep 2017 01:58) was approved by glai.

EVAL-CN0185-EB1Z Overview

CN0185 is a complete low cost implementation of an analog-to-analog isolator. The circuit provides isolation of 2500 V rms (1 minute per UL 1577).

The circuit is based on the AD7400A , a second-order, sigma-delta (Σ-Δ) modulator with a digitally isolated 1-bit data stream output. The isolated analog signal is recovered with a fourth-order active filter based on the dual, low noise, rail-to-rail AD8646 op amp. With the ADuM5000 as the power supply for the isolated side, the two sides are completely isolated and use only one power supply for the system. The circuit has 0.05% linearity and benefits from the noise shaping provided by the modulator of the AD7400A and the analog filter. The applications of the circuit include motor control and shunt current monitoring, and the circuit is also a good alternative to isolation systems based on optoisolators.



Equipment Needed (Equivalents Can be Substituted)

  • EVAL-CN0185-EB1Z Board
  • A multifunction calibrator (dc source), Fluke 5700A
  • A digital multimeter, Agilent 3458A, 8.5 digits
  • A spectrum analyzer, Agilent 4396B
  • A function generator, Agilent 33250A
  • Oscilloscope
  • A power supply, +6 V

General Setup

  • Connect the +6V power supply to the CN0185 power terminal J4
  • Connect DC source or Function generator to VIN+ and VIN-
  • Connect digital multimeter / spectrum analyzer or oscilloscope to output terminal

Test Setup Functional Block Diagram


DC Input Voltage Measurements





Frequency Response Measurements





Signal Generator Settings:
Output Waveform: Sinewave
Amplitude: ±20mV (40mVp-p)
DC Offset: 0

Connectors and Jumper Configurations


1 - Connect the +6V power supply to this screw terminal (J4)
2 - Connect the GND terminal of the +6V power supply to this screw terminal (J4)
3 - Connect the positive analog input signal to this SMB connector (J1)
4 - Connect the negative analog input signal to this SMB connector (J2)
5 - LK2 jumper Pins 1 and 2 provides the connection of the positive analog input signal to the AD7400 and pins 2 and 3 puts the input to ground
6 - LK1 jumper Pins 1 and 2 provides the connection of the negative analog input signal to the AD7400 and pins 2 and 3 puts the input to ground
7 - Connect the Digital multimeter if measuring dc input and Spectrum analyzer/oscilloscope if measuring frequency response to this SMB connector (J3)

The output is available through the J3 SMB connector or test point OUT


Schematic, PCB Layout, Bill of Materials

EVAL-CN0185-EBZ Design & Integration Files

  • Schematics
  • PCB Layout
  • Bill of Materials
  • PADS project
resources/eval/user-guides/circuits-from-the-lab/cn0185.txt · Last modified: 13 Sep 2017 01:58 by glai