REF3425: Current sink

Hello Scott,

In general this is the block diagram we would use to design REF34 as a current sink:

I would say your schematic does a good job of following this. Ensure that your EN pin setup allows for the datasheet recommendations: 

My only recommendation would be to add a bypass capacitor on the VIN pin in between 0.1µF and 10µF. 

Thanks,

Jackson