ADS8684: ADS8684 REFIO is just 0.8V

stephen zhang

Part Number: ADS8684

Tool/software:

Hi,

We set REFSEL to low, but REFIO only outputs 0.8V. RST/PD is high, so the chip is not in a reset state. Normally, when REFSEL is low, VREF_ADC should output 4.096V, right? What other reasons could cause this?
The circuit diagram is as follows:

8 months ago

0 Tom Hendrick 8 months ago

TI__Guru**** 181021 points

Hi Steven,

Do you have the ability to toggle the RST/PD pin? If you cannot do that with a GPIO on your controller, try shorting C702 with a tweezer and see if the reference starts up.

0 stephen zhang 8 months ago in reply to Tom Hendrick

Intellectual 370 points

Hi Tom,

I shorted C702, but the reference voltage still did not output. I changed another hardware board, and the REFIO voltage was only 0.07V.

+1 Tom Hendrick 8 months ago in reply to stephen zhang

TI__Guru**** 181021 points

Hi Stephan,

Can you provide a more comprehensive schematic and perhaps a timing screen shot of the power -on sequence?

0 stephen zhang 8 months ago in reply to Tom Hendrick

Intellectual 370 points

Hi Tom，

I will fly the wire to grab the timing diagram later. Can you help confirm the problem of AVDD2 first? AVDD2 is not connected to 5V, but disconnected. Will it have any impact?

0 Tom Hendrick 8 months ago in reply to stephen zhang

TI__Guru**** 181021 points

Yes - that needs to be tied to AVDD.

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ADS8684: ADS8684 REFIO is just 0.8V