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DAC8775: Output Zero Code Error

Nithin D
Prodigy 30 points
Part Number: DAC8775

Tool/software:

Hi team,

I am using DAC8775 for a product that's under development. 

Steps followed to configure DAC8775:

1. Reset Register(0x01) = 0x0001;

2.  Reset Config Register(0x02) = 0x0012;

3. Select Buck-Boost Converter Register(0x06) = 0x000F;

4. Configuration Buck-Boost Register(0x07) = 0x061F;

5. Select DAC Register(0x03) = 0x0020; // Selecting 1st channel

6. Configuration DAC Register(0x04) = 0x1001;

7. DAC Data Register(0x05) = 0x0000; //setting output count as 0.

Above are the steps followed to configure DAC8775 channel 1 to give output as 0V.

But when count is given as 0x0000, I receive 4.4mV as Output voltage. I am also unable to bring it down to 0V with calibration. 

Am I missing out on something?, or is this the minimum achievable.

Requesting your support in this regard.

BR,
Nithin

  • 0
    TI__Guru* 98025 points

    Nithin,


    I did run a quick test using the DAC8775EVM and when I power up the device and set the output voltage with a DAC code of 0x0000, I get an output of about 200uV out. This seems reasonable, so you should be able to get much closer to 0V than 4mV.

    For your setup, I don't see anything wrong. Going through the register settings, it looks like you've programmed it correctly, but you should check two things with a multimeter. First check the VPOS_IN_x and VNEG_IN_x are at +15V and -15V. If the supplies are bipolar, then the device shouldn't have a significant zero code error. If VNEG_IN_x is at 0V, then you might see the zero code error as significant (and maybe you would see 4mV).

    Second, I'd look at the reference voltage. In your register setting, it looks like you have it turned on, but definitely measure it with the multimeter. When I turned off the reference, I did see that the output went to about 2mV. It's a bit of an unexpected result, but one you should check.

    If you have a schematic, I could look it over.


    Joseph Wu