We are in the process of testing our dac circuit board design built with a DAC34SH84. We have confirmed our power supplies, confirmed we have read/write access to the registers and that our clock cleaner and synthesizer are locking. Note: our clocking system consists of an LMK04906 feeding an LMX2581 synthesizer with an LMK01000 directly feeding the clock to the dac.
We tried putting in our various trial settings and had no output. We then took a step back and tried outputting DC values using the sifdac(15:0) register with sifdac_ena enabled. Did we understand correctly that we should be able to see a DC value out of the DAC when we perform this test?
We then used the atest mode to gather additional information. Our TXENA pin is left open in our design (tied to a via) because we are using software control. When we try all of the atest values we have correct readings for everything except the DACx AVDD values. All of the DACx AVDD values are approximately 2.15V instead of the 3.3V in the expected value column. We have confirmed that the artwork pour for the AVDD voltage has 3.3V on the decoupling caps. I have also confirmed the artwork appears to be what I would expect. Would you have any idea how this voltage could have this value and is this likely to be causing our lack of output voltage? These reading were confirmed on two different prototype boards.
Is there something else we should look at or try?
Thanks for any help or suggestions.
Harold