DAC124S085: DAC not working

Hi,

First of all can you probe all signals together and send me clean scope plots to validate the frame.

Also how are you generating 3V reference for the device? Is this coming from a buffer? we need to drive this reference pin with very low impedance source as device doesnt contain any buffer and input impedance on this pin is 30K.

Also make sure that SYNC is not brought high before 16th SCLK fall edge, I am not able to see that timing from your scope shot. Please allow SYNC to stay one more SCLK low and bring it back to high for a check.

whats the Data bits (16bit ) you are feeding into DAC? is it 0x18FF ?

Regards,

AK

Hi AK,

Thanks for your quick response. The 3V reference is generated from an opamp.

I probed the SPI lines and hope this would help. Data given on all for channels is 0x18FF.

Output of DAC

VoA and VoB

VoC and VoD

Hi,

Thanks for these plots.

Can you probe Reference with a scope and meter when you are doing these test? I have a suspicion that your reference may not be stable and its drooping.

Regards,

AK

Hi AK,

The reference looks stable. I've attached scope shot for your reference.

Hi,

Your schematics and reference looks fine to me, other than in the EVM we have-used 4.7uF along with 100nF cap on Reference pin, ideally it should not matter. a 0.1uF cap is enough.

Can you try the following,

Input 0000 to DB[15:12] to go into normal operation mode.

Input 800 to DB[11:0] to output Vref/2

Let me know this helps.

Regards,

AK