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TMS320F28075: ADC channels ADCINA0, ADCINA1, and ADCINB1 have a 50-kΩ pulldown resistor to VSSA, what's it for?

Howard Zou
Genius 12365 points
Part Number: TMS320F28075

Why we have 50-kΩ pulldown resistor on these pins?

Any attention needed when designing the circuit for these pins?

  • 0
    TI__Mastermind 37790 points

    Hi Howard,

    This is due to the legacy design of the DAC channels that are internally connected to the ADC channels.  There was not an option then to isolate these loads through mux switches.  When designing circuits for these pins, specifically when these are used as ADC inputs, ensure that the source impedance of the circuits feeding to these inputs are low (in tens to low hundreds of ohms) so that signals will not be severely attenuated.  If source impedance cannot be reduced, consider adding buffers prior to driving these channels.

    Best regards,

    Joseph