LTC1666 - Vref - input resistor

Question

Hello fellows, I'm building my own DAC Eval Board and Im wondering to know .. 
 
 if the External Vref (suggested 2.5v) Can be set in a higher value? , like 5v. I only read about, adjusting Irefin current by resistor avoiding to source more than 10mA, but nothing about the Vref max limits values (May be, not exceed the sourcing values? +/- 5v). The higher Vref values in the DAC, the higher voltage range per counts (better for noise issues) 
 About the DAC inputs, Is it necessary to put 22ohms resistor between the FPGA ouput and the DAC input ports? (I'm interfacing a Cyclone V with the DAC) Datasheet suggest to use a resistor bank in Application Information Section - Suggested Evaluation Circuit. 
 
 Thanks in advance!

ADIApproved · Accepted Answer

Yes you can use a higher voltage, just adjust Rset accordingly. 
 
 It is not necessary to put resistors between the FPGA and LTC1666.)

ADIApproved · Answer

Yes, resistors are typically recommended to limit current, or dampen reflections. 
 
 What power rails do you have? You can make a negative rail with a SEPIC and then post regulate it with a negative LDO. 
 
 There are also parts like the LTM8049 that will give you both a positive and negative supply.

ADIApproved · Answer

let me know if you have any other questions