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PSoC 5, 3 & 1 MCU

JoLo_284096
New Contributor II

Dear all:

I am working in a project using de SAR_ADC_Seq component on PSOC5. I need to measure several currents. I am using INA138 from TI which give a output current proportional to the current to be measured. Adding a resitor to the output of the INA138 converts the ouput to voltage so I can measure them with the SAR_ADC. I have 8 channels in the ADC to measure 8 different currents. INA138 recommends to buffering the output signals (see attached image) before the ADC. My question: should I use a these buffers before the SAR_ADC_Seq?

The RL of the image in my system is 91K.

I dont see any data on the datasheet about the input impedance of the SAR_ADC_Seq and not any topic similar to this on Cypress comunities/forum.

If you need further details please do not hesitate to ask me.

Thanks in advance,

Joaquin.

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JoMe_264151
Expert II

Yes, you will need a buffer amplifier. To reduce device count etc I would suggest the following:

  • Separate the the analog mux and the ADC and build your own SeqADC
  • Use a PSoC5 internal buffer amp or a follower past the AMUX
  • Connect AMP output to ADC

This way you just need one internal OpAMP, no more external parts needed.

Bob

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2 Replies
JoMe_264151
Expert II

Yes, you will need a buffer amplifier. To reduce device count etc I would suggest the following:

  • Separate the the analog mux and the ADC and build your own SeqADC
  • Use a PSoC5 internal buffer amp or a follower past the AMUX
  • Connect AMP output to ADC

This way you just need one internal OpAMP, no more external parts needed.

Bob

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JoLo_284096
New Contributor II

Thank you Bob, as usefull as always. Great idea.

I will do so.

Regards,

Joaquin.

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