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DAC80504: Cannot output a valid voltage, This is the input signals. C

user4516881
Prodigy 20 points
Part Number: DAC80504

Hello.

I used DAC80504 chip in our board, But I didn’t get the output.

Can you help me? Thanks.

One DAC80504 connected to a MCU. The input pins of DAC80504 chip, CS, SCLK and SDI signals are generated by general IO ports of MCU with program. After the program is started, only the instruction for setting DAC0 register is sent, and no other instructions are sent.

The oscilloscope captures the input signal waveforms as shown in Figure 1.

Yellow is CS,

blue is SCLK,

purple is SDI.

SDO pin outputs data waveform, and REF pin outputs voltage 2.54v, but DAC0 output is 0V.

 The external connection of the chip is shown in Figure 2.

  • 0
    TI__Mastermind 18546 points

    Hi,

    Schematics looks fine to me. Since your RESETSEL pin is 3.3V, I expect power on reset value of DAC output should be at mid scale, thats 1.25V.

    1. Whats the value of DAC output at power on reset (dont write any data into DAC, just power up) ?

    2. Whats the data you are writing into device?

    3. Can you please keep CS signal low bit longer?

    4. Whats the load connected to DAC?

    Let me know the outcome of these and we can debug further.

    Regards,

    AK

  • 0 in reply to Akhilesh K
    Prodigy 20 points

    Hi, AK.

    Thank you for your attention and prompt reply.

    There's good news. After I sent the question, I happened to solve it. and I'll share the results here.

    According to my later test, the reason should be as follows:

    On my circuit, the DAC hardware configuration pins of REFDIV and GAIN are connected to GND, which means that when power on, the GAIN register settings are both 0. However, according to the data sheet of the device, this configuration mode is not recommended. For this reason, I added the instruction of software configuration in my MCU initialization program and changed the GAIN register settings to 1. After that, the correct voltage can be output.

    Regards,

    Song Yue.