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DAC8771: PVDD/AVDD Power on reset issue

user5163865
Genius 3525 points
Part Number: DAC8771
Other Parts Discussed in Thread: LM25180

Hi,

I asked about DAC8771 last week in the thread below.
https://e2e.ti.com/support/data-converters/f/73/p/792835/2933096#2933096
And I sent a customer's schematic to Garrett's PM.
Has he received a PM?
When buck_boost was turned on with load open, 0-24 mA Output mode, DAC_code = 0xffff, PVDD / AVDD was down from 15V to 5V.
This may be the cause of the failure.

PVDD / AVDD is supplied with 15V by R0.5Z-1215/P (RECOM).
https://recom-power.com/pdf/Econoline/R0.5Z.pdf
Also, I tested using the EVM. And PVDD / AVDD was supplied with 15V/3A DC. it's just Garrett said, under any conditions, the DAC8771 worked nomaly and never failed in my evaluation.
Accoding to IPVDD spec, It is clear that R0.5Z-1215 / P (RECOM) is not enough power supply.
However, I do not think that DAC8771 breaks down. I think that POR works when AVDD drops, can it cause a broken?
There may be another problem with customer's circuit I sent.
And do you think really need a 15V / 0.5A = 7.5W power supply? Since customers use at 500 ohm / 0-24 mA, they considered that the above power supply module was enough.
Can you suggest TI's power supply ICs and circuits?
I apologize for the inconvenience.
If you look at the customer's circuit. Please advise me.
At the same time, I will check again if the customer's DAC8771 is really broken.
Best regards,
Hiroshi
  • 0
    TI__Expert 5820 points

    Hello Hiroshi-san,

    I received your PM and sent an email to the address you provided. We can continue to discuss on this E2E thread or over the email, whichever you prefer.

    If PVDD/AVDD drops to this low below the recommended minimum operating voltage the device will likely reset, but this should not cause damage. I suspect this is what is happening and why you only see the issue when you 'hot' connect the DMM.

    The power supply you are using can only support 33mA while the DAC8771 can consume an average DC current of ~100mA. You will need to use a different supply.

    The peak inductor current of 500mA is supplied from the bypass capacitance so the supply does not have provide DC 500mA.  I would target 150mA DC and add extra capacitance on AVDD/PVDD. I am not sure on specific power ICs so you can use the parametric search or post on the power management forum. In a reference design we recently did with DAC8771 we used LM25180 for an isolated supply. You can view the reference design at the link below.

    http://www.ti.com/tool/TIDA-01535

    Thanks,
    Garrett

  • 0 in reply to Garrett Satterfield
    Genius 3525 points

    Hi Garrett-san,

    Thanks a lot.

    I tested again with the evaluation board based on your answers.
    Although I tested and changed various conditions, the evaluation board was robust and did not break down.

    On the other hand, the customer's board did not return even with HW RESET.
    As the next step, so the customer changes to a 200mA power supply, I expect that major issues will be avoided.
    Thank you again.
    Hiroshi