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Ringing 1 Volt output in the DAC714 while switching off the power

Shibu K. Mathew
Prodigy 30 points
Other Parts Discussed in Thread: DAC714

Dear All,

I use a DAC714 for powering the control input of a High voltage Power supply module (from TP5). I use the following circuit for this purpose.

3583.hvps.pdf

When I switch off the mains power supply I see an output voltage which rises up to 1 Volts for few secs

 and then comes down to zero (may be little bit up and down - ringing in between) .  I keep the A1 high after latching

the data bits.

regards,

shibu

  • 0
    TI__Mastermind 46290 points

    Shibu,

    Can you get a capture of this ringing? It would be helpful to also see a capture of each of the supply lines and the ringing output in one capture.

  • 0 in reply to Kevin Duke
    Prodigy 30 points

    Dear Kevin,

    Unfortunately I am out of town, will be able to send the capture only after I reach home, might be after a month.

    Hope you had a look at the circuit, The power to the DAC is supplied by a normal isolated regulated power supply, ofcourse

    with some capcitor filters in the outpu. I have not checked the power supply ouput, does this happen because of the power supply

    fluctuations due to discharge of the filter capacitors?

    As I do not make any changes in the SDI, CLK, A1 and CLK pins, I thought the output should not change when I do power shutdown,

    even when the supply voltages reach zero slowly because of the filter capacitors. Is there a way to avoid this?

    regards,

    shibu

      

  • 0 in reply to Shibu K. Mathew
    TI__Mastermind 46290 points

    Hello Shibu,

    I did look at your schematic but it was not clear to me that the DAC was driving a reactive load. Can you highlight the load the DAC expects to see with complete values for the resistors and capacitors?

  • 0 in reply to Kevin Duke
    Prodigy 30 points

    Dear Kevin,

    The input impedence of the HV power supply module which I am controlling with this DAC is around 220K. But this effect is seen even with out connecting the HV module, i.e. when I connect the output to a normal analog multimeter. The needle goes upto 1 Volts and then comes down and then a small amplitude ringing close to zero.

    with regards,

    shibu