Can I power a DAC that has a 4.096V internal reference from VCC=3.3V if I use a 3.3V external reference?

Question

LTC2631 comes with options of an internal reference of 2.5V (-L) or 4.096V (-H). You can also use an external reference.

Can I power a -H part from 3.3V if I configure it for external reference and connect 3.3V to the reference pin? 
 The part I'm using is a -LZ, which means will default on power-up to internal reference.

But I will immediately change to internal. 
 Will it cause a problem when it briefly tries to drive its 4.096V internal reference while VCC=3.3V?

iandal · Accepted Answer

Hi, 
 In that short span where the internal ref and external ref are both active, current will flow from internal to external (4.096V -> 3.3V). This current should be limited by the short circuit current spec of the LTC2631's internal ref (p9 on the datasheet) to 4.3mA typical. LTC2631 should be able to bear this, what you should check is if your external ref chip can sink this 4.3mA of current (possibly more as this is a typical spec. 
 The best case would be to have your external ref disabled or disconnected to the LTC2631 prior to disabling the internal reference. 
 ~ian)