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DAC80508: How to connect external reference

Shalom Kattan
Prodigy 80 points
Part Number: DAC80508

The internal reference is enabled by default at power up.  If I connect an external reference how do I avoid contention since both the internal and the external reference will be ON until I disable the internal one?

  • 0
    TI__Guru 53773 points

    Hi Shalom,

    Yes, these two references will try to conflict with each each other until the internal one is disabled.  The internal reference can source or sink about 5mA before it clamps to the supply rail.  For this case I recommend that you place a resistor between the external reference and the reference pin, maybe 500Ω.  This will limit the current flowing between the references.  The current will not damage the device.  In addition, the reference is buffered internal, so there is very little input current, so the reference error created by the series resistor should be minimal.  The capacitor on the reference pin gives the added benefit of noise filtering created by the RC.


    Thanks,
    Paul