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DAC7760EMC-EVM: DAC7760 EVM isn't responding.

user5766181
Prodigy 40 points
Part Number: DAC7760EMC-EVM
Other Parts Discussed in Thread: DAC8760EVM, DAC8760, DAC7760

I want some help to oprate EVM normally. I supplied +15.0V to J4-1pin (5mA consumed), -15.0V to J4-3pin (1mA consumed) and J4-2pin connected to GND.

But ,according as TI DAC8760EVM tool, DAC resistor wasn't correctly respond. All-zero respond was shown.

For debugging, I checked signal behavior of CS_AO,SCLK_AO,MOSI_AO and MISO_AO signals. The result was

 CS_AO: Always L(GND level)

 SCLK_AO: Correctly changed

 MOSI_AO: Correctly changed

 MISO_AO: Always L(GND).

Also, I Checked DVDD voltage that was +4.7V and it seems to be correct.

What can I do for further debugging?

  • 0
    TI__Mastermind 46290 points
    Hello,

    It is very peculiar that SCLK and MOSI are toggling as appropriate while the CS signal is not active at all. Can you first verify that both LEDs on the SM-USB-DIG are illuminated? This suggests that the device is enumerated and communicating with the PC correctly.

    Can you share the captures of the SPI transactions to see what may be happening with the CS line? Can you ensure that both sides of the digital isolator are supplied appropriately?
  • 0 in reply to Kevin Duke
    Prodigy 40 points

    Thanks for your comment,Mr. Duke.

    I checked as follows.

     1. Both LEDs in SM-USB-DIG is illuminating green.

     2. I checked both side of digital isolator (ISO7641)

         VCC1-GND1 (SM-USB-DIG side) : +5.02V

         VCC2-GND2 (DAC chip side) : +4.62V

     3. Captured SPI signals is attached

       In this photo, Yellow line shows CS_AO line, Green line shows SCLK, Pink link shows MOSI, and Blue line shows MISO.

       Both signals was captured when I "Read all-reg" from DAC8760 tool.

     

        These photos shows that Green(SCLK) and Pink(MOSI) is adequately toggling, but the others don't.

  • 0 in reply to user5766181
    TI__Mastermind 46290 points
    Hello,

    If the oscilloscope is setup to capture falling edges on the CS trace, is anything triggered / captured?
  • 0 in reply to Kevin Duke
    Prodigy 40 points

    Thanks for your comment.

    I checked CS(LATCH) signal transaction. It seems to have never rising/falling edges, when I captured with CS trace edge's trigger,

    trigger didn't occured.

    OK. I will check SPI transction not from SM-USB-DIG but from another SPI master device which can make CS signal.

  • 0 in reply to user5766181
    TI__Mastermind 46290 points

    Hello,

    That is very odd. This board does not have any jumper configurations, so for some of the digital to behave correctly but not the CS is very confusing to me.

    Is it possible for you to check the SM-USB-DIG CS behavior without connecting it to the EVM board to see if it is toggling correctly? Perhaps somehow the CS pin of the DIG is damaged.

    An alternative would also be as you've proposed to use another host device to interface the EVM with a known working CS behavior.

  • 0 in reply to Kevin Duke
    TI__Mastermind 46290 points
    Hello,

    Do you have any update for us on this topic?
  • 0 in reply to Kevin Duke
    Prodigy 40 points

    Thank you for consideration.

    I tried to connect another SPI master device to DAC7760 directly.

    And , from the waveform,  it is observed that LATCH signal which is input of DAC7760 chip OUTPUTS some voltage.

    So, I concluded that I broke the chip by my mistake. I will exchange it for another one.