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DAC5672: control question: Cannot make IOUT updated

[FAE] Andrew Wang
Genius 10685 points
Part Number: DAC5672

Hi Team,

Customer try to control our DAC5672 EVM with their MCU but it doesn't work. The waveform capture is attached as bottom.

Because it's our EVM, so I assume this is pure software issue.

Here is the setting, please kindly teach me what is correct steps to talk to device, thanks!!

MODE = High , Dual Bus

SLEEP = Low, Operating Mode

CLKA, CLKB, WRTA, WRTB, are sync with same clock pulse at 100nS

1. Customer asked tLAT Clock latency (WRTA/B to outputs) min is 4 clk，do we need to continuously providing 4 clk pulses for CLKA, CLKB, WRTA, and WRTB?

2. If CLKA, CLKB, WRTA, WRTB only needs one clock pulse to update DAC，What are missing steps before IOUT get updated?

Many thanks!!

Andrew

 

  • 0
    TI__Mastermind 20541 points
    Hi Andrew,

    I am looking into this question. I will reply to you by tomorrow.

    Regards,
    Neeraj
  • 0 in reply to Neeraj Gill
    TI__Mastermind 20541 points

    Hi Andrew,

    1. Yes you are correct you will need 4 continuous clk pulses and on next pluse it should update your output.

    Regards,
    Neeraj

  • 0 in reply to Neeraj Gill
    TI__Genius 10685 points

    Hi Neeraj,

    Problem still not fix.

    Customer shown the update waveform and they did 4 continuous clk pulses, do you think there is any other possibilities?

    Thanks!!

  • 0 in reply to [FAE] Andrew Wang
    TI__Mastermind 20541 points

    Hi Andrew,

    From the screen shot it seems like customer is only toggling WRTA once where as CLKA is toggled 4 times.  These two always should match as the WRT is used to latch the data in before it goes to the DAC.

    Also looking at the Iout it seems like customer is looking at output through the transformer. As you might know transformer does not allow DC signal to pass and behave somewhat like and band-pass filter. When the Iout is updated it produces sharp edge the transformer allow some frequencies to pass but when the output settles to a DC value the transformer does not pass it through. Ask customer to bypass the transformer. If the customer is using the DAC5672EVM they can bypass the transformer on CHA by removing the transformer T1 and populating R10 = R15 =  R25 = 0 ohm and DNI R7.

    Also find the screen shot with transformer bypassed below. In my setup I have CLKA AND WRTA tied together.

    Regards,

    Neeraj Gill