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TMS320F28377D-EP: Buffering external ADC reference - OPAMP selection

Josef Rypar47
Prodigy 240 points

Part Number: TMS320F28377D-EP
Other Parts Discussed in Thread: OPA320, OPA350

Hello,

the TRM for TMS320F28377D-EP (SPRUHM8H, revised January 2019 ) recommends in section 11.3.4 Designing an External Reference Circuit to use "precision OPAMP with good bandwidth and low output impedance".

As an example there are OPA320 and OPA350 with bandwidths 20MHz and 38MHz.

Can you please quantify what do you mean by "good bandwidth"? Is it 5MHz, 10MHz, 20MHz....? I expect the required bandwidth is related to sampling rate - can you describe the relation? I cannot use OPA320 or OPA350 because I need -55°C part, ideally in dual or quad package configuration.

Thank you, Josef

  • 0
    TI__Mastermind 26220 points

    Hi Josef,

    The op-amp primarily needs to have enough bandwidth and drive strength to charge the internal S/H capacitor within the ACQ_PS window. Based on the input circuitry you have, the op-amp bandwidth will change.

    I wanted to make you aware of this tool: http://www.ti.com/tool/analog-engineer-calc

    If you know the ADC type, resolution, Csh, full scale range, and acquisition time it will calculate the required bandwidth of the op-amp for you.

    Hopefully this helps you narrow down the search to an op-amp with that required bandwidth and the other specifications you need.

    Best Regards,

    Marlyn