DAC1220: unexpected output when system power up.

Hugh Yang

Part Number: DAC1220
Other Parts Discussed in Thread: DAC8560, DAC11001A

Hi Team,

Hope everything goes well. One customer were facing a problem while using our DAC1220.

Q: when system power up, it will takes 100ms for MCU(F2803x) to wake up. Before F28035 enter work mode and don't have any communication with DAC1220, the output of DAC is 2.0V, which is unexpected in the design. Check the SPI waveform: CSI/ CLK/ MOSI are at high level before MCU power up. If I'm right, the DAC1220 will not output, but from the waveform, the output is about 2V before any communication. But if customer use DAC8560 instead of DAC1220, the problem is solved. Could you help us find the root cause and solution?

Pink:CSI Green: Mosi Blue: output of DAC1220 yellow:CLK.

Many thanks,

Hugh

over 1 year ago

0 Paul_Frost over 1 year ago

TI__Guru 53573 points

Hi Hugh,

By default, the DAC1220 uses a two's complement data format by default. The DIR register is 0x000000 by default and thus we have an output at bipolar zero, which should be mid-reference voltage.

Thanks,

Paul

0 Hugh Yang over 1 year ago in reply to Paul_Frost

TI__Intellectual 910 points

Hi Paul,

Thanks for your support. BTW, if customer wants choose the 20bits DAC and the default value is 0, any suggestion for them to replacement? P2P is better.

Br,

Hugh

0 Katlynne Jones over 1 year ago in reply to Hugh Yang

TI__Mastermind 34098 points

Hi Hugh,

Here is a list of our 20-bit DACs:

https://www.ti.com/data-converters/dac-circuit/precision/products.html#84=20%3B24&

We don't have any P2P, so the best option would probably be the DAC11001A. The output powers up to zero scale.

Best,

Katlynne Jones

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DAC1220: unexpected output when system power up.