AD73360 ( Overdriving REFCAP with an external refence)

Hi,  I would like to ask some qustions on the AD73360 REFCAP.

Earliest replies from the responsible staff member for this product would be appreciated.

I'm reffing to the AD73360 Rev. B datasheet.

Q1. In PIN FUNCTION DECRIPTION,  there is a description that the REFCAP  pin can be overdriven by an external reference.

Can it really driven by an external reference?  The reason why I ask such a question is as follows.

  The REFCAP should be a low impedance output.  Driving this pin with another low output impedance refence

would make a short-cicuit of the two refenrences, and this would not be acceptable.

Q2: Assuming an external reference  can be used to overdrive the REFCAP, what would be the requirements for it in terms of electrical specification?

Best Regards,

Lux

  • Hi Lux.

    Sorry for the delay. This question got misrouted.

    Although the AD73360 datasheet mentions using an external reference, there are some things to note:

    1. When enabled, REFCAP reflects the internal reference voltage and the reference voltage being used by the sigma-delta converter. If successfully overdriven, REFCAP then reflects the external reference voltage being used by the sigma-delta converter.

     

    1. From simulating the design:

    To overdrive REFCAP “high”, the external reference would need to have (approx) > 0.5mA current source capability.

    To overdrive REFCAP “low”, the external reference would need to have (approx) > 2mA current sink capability.

     

    1. REFCAP and REFOUT are each buffered from the reference inside the IC

    Best Regards

    Meghan