I am using DAC9881 with the following configuration :-
1) Gain = 0
2) Unsigned binary input mode
3) Standalone mode
4) VREFH = 4.75V
5) VREFL = -0.1V
I am using Kelvin connections for the reference input as recommended in the datasheet.
6) DAC output is connected to the non inverting input of a source follower.
Issue : -
- With input code all zeroes (00000h), I am getting 10mV at DAC VOUT.
- The output doesnt change as I increment the digital data, until it reaches abt 5500 codes ( 10mV at DAC VOUT ideally corresponds to abt 5500 codes from zero in the dac register)
- From abt 5500 codes, the output starts responding with incrementing input digital data, and I am able to reach VREFH ( 4.75v ) when I give all ones to the DAC
- With Gain pin set to high, the DACOUT voltage with all zeroes digital input drops to 7mV ( but the same thing happens here, it doesnt respond till some code and then it starts working fine)
Checks done : -
1) Checked the timing of CS, SCLK, SDATA, LDAC - they are fine
2) Checked the data which is coming out of SDOUT, its giving out the previous data, and its correct, (I checked for codes starting from 00000h to 00002h and they are all correct) which means data latched into the input shift register is correct
Please help in debugging this issue