UA723: UA723CDR have output voltage jitter

Kevin Huang8

Part Number: UA723
Other Parts Discussed in Thread: LM337L

The output voltage of uA723 will drift with time, some chips become larger, some chips become smaller, and there will be small jitter when changing(Note: The width of the time axis is 12 hours, and the voltage changes between 200mV~300mV).

In addition, have confirmed that the board temperature is stable, and the voltage change is not caused by temperature.

At the same time, when the output voltage changes, the Vref voltage of uA723 is indeed changed.

The circuit is designed with reference to Figure 8. Negative Floating Regulator of uA723 datasheet

over 2 years ago

0 Jason Song over 2 years ago

TI__Mastermind 23361 points

Hi Kevin,

UA723 is affected by the so-called Zener walkout as discussed in the following post.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/592151/ua723-problem-with-regulation-waaay-out-of-spec

Previously we were also trying to capture the reference drift of UA723, and here is the data for you to reference.

UA723 drift_rev.pptx

Regards,
Jason Song

0 Kevin Huang8 over 2 years ago in reply to Jason Song

Genius 3005 points

For Zener walkout affect,

are there any root cause to improve this issue?

or suggest other replace components?

0 Jason Song over 2 years ago in reply to Kevin Huang8

TI__Mastermind 23361 points

There are a few E2E posts that have discussed this problem in great details

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/693040/ua723-drift-is-a-one-time-thing-zener-walkout-that-stabilizes-after-time-output-voltage-is-drifting-during-test

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/592151/ua723-problem-with-regulation-waaay-out-of-spec/2183054#2183054

I would suggest checking the two posts, and let us know if you were to take any of the suggestions in the posts.

We don’t have any negative LDO below -40V in our portfolio today. You have looked into the LM337L family and see if that works here but it will only support up to -40V.

Regards,
Jason

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UA723: UA723CDR have output voltage jitter