DAC60508: DAC output always 0 at GAIN REFDIV-EN = 0

Marco Florcruz

Part Number: DAC60508

Hi,

I would like to use a DAC output > 2.5V internal VREF, so I disabled reference divider, and enabled GAIN to accomplish this (GAIN REFDIV-EN = 0, BUFFx-GAIN = 1). I only had VDD = 3.3V since this is the max value I need. I expect that value < 3.3V should be allowable, and maybe clamp at 3.3V if Iset a value that will exceed this; but DAC output is always at 0V when I try various values below 3.3V.

Playing around the settings, any setting with REFDIV-EN = 0 does not any output at DAC:

- REFDIV-EN = 1, BUFFx-GAIN = 1, DAC output is set as expected.

- REFDIV-EN = 1, BUFFx-GAIN = 0, DAC output is set as expected.

- REFDIV-EN = 0, BUFFx-GAIN = 1, DAC output is always 0V.

- REFDIV-EN = 0, BUFFx-GAIN = 0, DAC output is always 0V.

Anything I could look at to make REFDIV-EN = 0 to work? Thanks!

over 4 years ago

0 Paul_Frost over 4 years ago

TI__Guru 52663 points

Hi Marco,

This will be tough. The reference alarm is in place to ensure that there is enough headroom between the supply and the reference voltage. This is not due to a limitation in the reference, but really the switches in the resistor ladder require headroom. So this alarm state is important.

So your desired configuration will not be possible with the internal reference.

A possible alternative would be to use an external reference, say 2.048V, with a BUFF-GAIN of 2x, resulting in an ideal output of 4.096V, but it will clamp at ~3.3V.

Thanks,

Paul

0 Marco Florcruz over 4 years ago in reply to Paul_Frost

Prodigy 20 points

Thanks Paul, we missed the detail on the headroom. We'll work around it.

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DAC60508: DAC output always 0 at GAIN REFDIV-EN = 0