Which should I connect REFLO of AD9744 to ? ACOM or AVDD ?

Anyone could answer this question ? or should I made a backup that the REFLO pin can be connected either to AVDD or AGND ?

The design of the internal reference was changed slightly in the third generation TxDAC AD9744 such that REFLO should always be tired to ACOM. To use an external reference you just overdrive the internal reference's output current source which I think is about 200 uA.

Doug

Thanks! I think the reference schematic of AD9744 should be updated accordingly  I found that Agilent 33220A (which uses AD9744) tied REFLO to AVDD, is there any drawbacks in doing so ? should I leave a backup plan where REFLO are tied to AGND via a 0Ohm resistor and a DNP resistor pulled to AVDD?

The internal functioning of the REFLO and REFIO pins was changed to allow certain "test" modes used during final test in the factory. Agilent is going against our recommended use of this pin on the AD9744.

Hi, dmercer

In an official FAQ of analog, AD9748_REFLO pin 

it says that the REFLO should be connected to AVDD, I am confused now. Where on earth should the REFLO of AD9744 be connected to?

Hi -

You should connect REFLO to ground when using either the on chip reference or a board level reference. What Keysight as done is not harmful. But it is not what we recommend.

Thanks