UC1846: UC1846 reference pin recommended external capacitance

Nandha Kumar5

Part Number: UC1846
Other Parts Discussed in Thread: , UC1901, UC1843, UC1825

Hi,

The datasheet for UC1846 shows a recommended external capacitance in the range of 1-2.2uF. However, this specification is absent in the UC1846-SP datasheet. We have been using an external capacitance of 10uF on the ref pin for quite a while now. Could someone confirm if this is a stringent requirement. If not, what deviations in performance are expected under all operating conditions. I am drawing a current of 5mA from the ref pin. Let me know if further details are needed

Thanks and regards

Nandha

over 4 years ago

0 Daniel Hartung over 4 years ago

TI__Mastermind 21965 points

Hey Nandha,

The UC1846-SP mentions it in the layout guidelines.

Adding more capacitance will not be an issue however. This will only improve transients on the pin.

If you don't have a noise decoupling capacitor however, I would suggest adding that.

Thanks,

Daniel

0 Nandha Kumar5 over 4 years ago in reply to Daniel Hartung

Intellectual 470 points

Hi Daniel,

Can I go ahead and use this justification for all the UC series PWM controllers and UC1901 too.

Thanks

Nandha

0 Daniel Hartung over 4 years ago in reply to Nandha Kumar5

TI__Mastermind 21965 points

Hey Nandha,

All is a bit too strong of a statement.

Its likely, but I would want to check them all.

I can confirm the UC1901, are there others you want clarification on?

Thanks,

Daniel

0 Nandha Kumar5 over 4 years ago in reply to Daniel Hartung

Intellectual 470 points

I am currently using UC1825 and UC1843 other than the UC1846. I'll let you know if other information is needed

Thanks

Nandha

0 Daniel Hartung over 4 years ago in reply to Nandha Kumar5

TI__Mastermind 21965 points

Hey Nandha,

I can confirm those three as well.

Thanks,

Daniel

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UC1846: UC1846 reference pin recommended external capacitance