BQ25790: ADC enable fail

Yishan Chen

Intellectual 1800 points

Part Number: BQ25790

Tool/software:

Hi Jeff,

We encounter a issue that we can't enable ADC, below is the description.

When customer remove battery and use adaptor to power the charger. They will restart the initialization.

When the adaptor is plug-in, they will delay 500mS and start to write the register, all the register can be wrote except ADC_EN.

They can't enable the ADC. But if we delay about 2s, all retry couple times, then we can enable ADC.

What is the potential reason here?

Besides, I want to know if the voltage in VBUS already stable, how many seconds we need to enable ADC? This is relevant to the power sequence.

Thank you,

Yishan Chen

3 months ago

0 Michael Bradbourne 3 months ago

TI__Genius 9110 points

Hi,

500 ms is too short between adaptor plug-in and setting ADC_EN. The full power up start up sequence has not completed by that time. Did you try any intermediate values between 500 ms and 2s?

Best regards,
Michael

0 Yishan Chen 3 months ago in reply to Michael Bradbourne

TI__Intellectual 1800 points

Hi Michael,

Since 500mS is too short, could you please give us a data about the power up sequence duratoin.

Thank you,

Yishan Chen

0 Michael Bradbourne 3 months ago in reply to Yishan Chen

TI__Genius 9110 points

Hi Yishan,

I have looked at the documentation, and it still seems a little unclear to me. I think 1 second should be long enough. Jeff will be back in office on Monday and may have a clearer answer.

Best regards,
Michael

0 Yishan Chen 3 months ago in reply to Michael Bradbourne

TI__Intellectual 1800 points

Hi Michael and Jeff,

Do we have any update for the time duration?

Thank you,

Yishan Chen

0 Jeff F 3 months ago in reply to Yishan Chen

TI__Guru**** 169756 points

Hi Yishan,

The only delay that I am aware of is 150ms from VBUS applied until REGN comes up when no battery is attached. Is it possible that the watchdog timer is clearing the EN_ADC bit?

Regards,

Jeff

0 Yishan Chen 3 months ago in reply to Jeff F

TI__Intellectual 1800 points

Hi Jeff,

They already disable the watchdog, do you think there are any other potential reason for 'can't enable ADC'.

Thank you,

Yishan Chen

0 Jeff F 3 months ago in reply to Yishan Chen

TI__Guru**** 169756 points

Hi Yishan,

There is no other reason for EN_ADC bit = 1 to auto set back to 0.

Regards,

Jeff

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BQ25790: ADC enable fail