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TMS320F28069 ADC question

Todd Solak
Intellectual 1425 points

Other Parts Discussed in Thread: TMS320F28069

 Hello,

With reagrds to the ADC of the TMS320F28069 device, are there any clamp diodes, or other connection, to a power rail?  I want to use an ADC input to monitor an external signal.  I need to determine if I have any potential sneak path, if the external input is presenting voltage, but I am in a power off state (V3.3 is off).   The impedance model in the data sheet does not show such a device, but I don’t consider that definitive.

Thank you for yuor help!

Todd

  • 0
    TI__Expert 8500 points

    Todd,

    There is a sneak path. In fact the datasheet warns against powering pins prior to powering the device. See section 6.5 Power Sequencing. This warning is especially true for the analog pins. The impedance model is purely to help customers analyze how their external circuit will affect the sample time requirement of the ADC.

    Regards,
    Dave Foley

     

  • 0
    TI__Intellectual 1105 points

    Todd,

    For the TMS320F28069 device, all GPIO and ADC pins have clamp diodes.  Each IO is allowed plus or minus 2mA of continuous current and up to 20mA for the whole device.  For more information, look at section 5.1 in the data sheet.  Specifically the line about input clamp current and note (3) below the table.

     

    Regards,

    Ricky Rosinski