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DAC8411: DAC8411

Bob Rowland
Prodigy 180 points
Part Number: DAC8411
Other Parts Discussed in Thread: DAC8801,

I was testing a DAC8801 using the DAC8801 Eval board. The SPI signals are coming from ports on an STM32F407 and are all about 3.3V signals. The DAC8801 worked very well, but we decided we needed a voltage source and wanted to eliminate the external amplifier. So we had a DAC8411 overnighted to us and connected it to the same setup using a 5.0V supply for +5VA. The DAC8411 supply is 3.1V. It didn’t work. When I checked the SPI signals SYNC (CS) looked good, but SCLK and DIN were badly loaded. The SPI signals are configured with an active pull up. I added 1K pullup resistor on the CS, the SCLK and the DIN signal, pulled up to the +3.1V supply. This improved the DIN signal, but the SCLK amplitude is still only 0.5V. When the STM32F407 is connected to the DAC8801 all of the SPI signal amplitudes are 3.1V. Do you have any idea why the DAC8801 is loading my SPI signals?  We have a very tight schedule and need to get this working in the next couple days.

Thanks,

Bob

 

  • 0
    TI__Guru 52663 points
    Hi Bob,

    I do not think the DAC8411 will be doing anything to load the pins directly. I think more likely this is a wiring issue. Are you using a DAC8411 EVM board, or just he device? Can you share your schematic?

    Do you have any series resistance on the digital pins?

    Thanks,
    Paul
  • 0 in reply to Paul_Frost
    Prodigy 180 points

    Hi Paul,

     Thanks for the quick response. I am using the DAC8411 Eval board. I have come to the conclusion that the DAC8411 on the board is damaged. I have the Jp2 connected to the 3.3V supply and with nothing connected to the SPI lines except 1K pull up resistors, the DIN signal, pin 3 on the DAC8411 is 0.5V. When I turn off power and measure the resistance between pin 3 and ground it is 9Ω. I was pretty careful with this board, keep it in the antistatic bag until connecting power to it, but I suspect it was probable something we did here that damaged it. We have another eval board coming today, I will measure the pin 3 resistance before connecting power to it.

     Thanks for your help.

     Bob