DAC8760: The technology issue for DAC8760

Zhang,

I'm not sure I understand what the second point refers to, but it is unlikely unrelated to the first point.

The DAC output cannot reach 0V with a zero code because the device is operated with a unipolar supply with AVSS at ground and AVDD at a positive voltage (maybe 15V?). The output buffer of the DAC is an opamp and the output of the opamp can get near ground but not exactly to ground when the negative supply is at ground. This is the footroom required for the device described on page 7 of the data sheet showing the voltage from AVSS to the VOUT zero scale.

The only way to drive the opamp buffer output to ground is to use a bipolar supply, with AVSS lower than ground preferably greater than 500mV.

I have seen cases where a small negative supply is generated from for the AVSS for this part. The LM7705 can be used for this purpose. While, this negative supply is about -0.23V, it may be enough for most cases of operation down to GND. I did find an E2E post about it here:

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/358718/dac8760-running-with-single-supply-0v-12v

And there was another post about using an LM27761 for a -1.5V supply here:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/683883/lm7705--0-5-v-source-for-avss-dac7760

Joseph Wu