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differential interfacing to the AD7356

Question asked by IPGEngineer on May 29, 2012
Latest reply on Jun 1, 2012 by ClaireL

Hello together,


I'm currently working on an high voltage 8 channel data acquisition system controlled by an Cyclone II FPGA. The general requirements are:


- 8 fully differential input channels

- precision measurement

- source independent measurement

- Signals from DC to 1MHz

- Input voltage range: (Up-Un) = -30V .. +30V

- Common Mode range (Up+Un)/2 = +-80V

- ESD & over voltage protection

- small package size, SMT

- ease of use (digital interfacing) -> SPI, I2C


My research showed that the 5MSPS, 12bit ADC AD7356 could be the fitting candidate. Analog proposes the AD8138 for analog interfacing. In an older version of our system we use an Instrumentation Amplifier (IA) circuit, build from single components (2 input amplifier, 1 differential amplifier, resistors and capacitors for decoupling and filtering).


Now my questions:

  • Do you think the AD7356 is fitting our requirements?
    • Is there an easy to use 8 channel ADC on the market which doesn't require an LVDS connection
  • Is there any integrated fully differential IA available, which can drive the ADC?
  • What about the input stage? Is a simple voltage divider OK for non invasive measuring? (see requirements.pdf)


I attached an *.pdf document which lists the requirements and explains our status quo.


Thank you in advance.

Regards Christoph