Could you clarify how to connect an external reference to the ADuC7024 part?

Could you clarify how to connect an external reference to the ADuC7024 part?

Could you also clarify the correct MMR settings for an external reference?

  • 0
    •  Analog Employees 
    on Jul 7, 2010 5:59 PM
    The attached diagram shows the reference structure for both the internal DAC and ADC.
    If you are connecting an external reference to the Vref pin, then  set REFCON.0=0. In this case, very little drive is required as the internal reference (~10uA only) is disconnected from the external reference pin. You should note however, if REFCON.0=0, the internal reference can no longer be selected by the DAC as it is disconnected from the 470nF external cap.  On the larger pin parts (ADuC7024/25/26/26/27/28/29), this is no problem as an external reference can be connected to the DACref pins.
    However, if the ADuC7019/20/21/22 want to use an external reference for both the DAC and ADC, the Vref based external reference must be capable overdriving the internal reference.