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DAC084S085: OFFLINE REQUEST

user6083619
Prodigy 180 points
Part Number: DAC084S085

Dear Sir:

I'll send you a question, DAC084S085 startup sequence.

When system start DIN and SCLK port voltage of DAC084S085 was midpoint potential voltage.

DAC084S085 was conected to MCU and we found MCU makes midpoint potential voltage.

But I'm confused about this voltage wave, rise rapidly and fall slowly in 500us.

Midpoint potential voltage is VCC/2 for general IC.(VCC is Power supply voltage.)

So please check wave figure and judge this midpoint potential voltage will make risk or not.

I'd send you wave figure, if I get your e-mail immediately.

Sincerely, YUZURU

  • 0
    TI__Mastermind 46290 points

    Hello,

    At this point the issue seems a bit unclear. Would it be possible for you to post the waveform or a schematic?

  • 0 in reply to Kevin Duke
    Prodigy 180 points

    DAC084S085_OFFLINE_REQUEST.pdf

    Thank you for your message.

    Sorry, I can't attached Schematic file.

    So I attached PDF of waveform.

    DAC connect MCU directly, no dumping resistor, pulled-up resistor and pulled-down resistor.

    SYNCn = H is fixed during Power ON.

  • 0 in reply to user6083619
    TI__Mastermind 46290 points

    Hello,

    I think I understand the situation you are asking about, but I want to be sure.

    The MCU is controlling plots 3 (purple / DAC DIN pin) and 4 (green / DAC SCLK pin). Meanwhile, plot 1 (yellow / DAC VA & VREF) is already stable at 3.3V (although it looks like the plot is 1V / division and something closer to 4.3V).

    For some reason, your MCU has this voltage spike / decay behavior upon powering up the SPI peripheral. The SYNC pin is not pictured.

    Since the VA supply is already stable, there is no violation of the absolute maximum ratings table and therefore I do not see any cause for risk to damage the device. If what you say is true concerning the SYNC pin, then there is also no risk for the device to be accidentally latching input data.