TPS62140: Input noise

Lars Roger Solem

Prodigy 170 points

Part Number: TPS62140

Tool/software:

Hi,

We are testing TPS62140 in our application. Problem is, there are a lot of input noise generated on the 12V input.

The spikes are more than 1.5V peak-peak and changing with load.

Scope picture:

We have tried a lot of things, but can't find any solution here.

Tested:
- place a capacitance of 0.1 uF from AVIN to AGND, to avoid potential noise coupling

- 10-100 nF input capacitors

- 10-100 nF output capacitors

- Different inductors

over 1 year ago

0 Lucia Gao over 1 year ago

TI__Mastermind 31951 points

Hi Lars Roger Solem,

Thanks for your reaching out. We will check your question and get back to you during these days. Thanks!

BRs

Lucia

0 Colin Chen over 1 year ago in reply to Lucia Gao

TI__Mastermind 21981 points

Hi Lars Roger Solem,

Put a Cin=0.1uF be closest to device should be effective to reduce high frequency glitch.

Besides you may pay more attention to test method properly and using probe with ground lead to get a small loop to ease measurement error.

Thanks

Colin

0 Colin Chen over 1 year ago in reply to Colin Chen

TI__Mastermind 21981 points

We suggest test method like below:

Colin

0 Lars Roger Solem over 1 year ago in reply to Colin Chen

Prodigy 170 points

Hi Colin,

Filtering the noise away on the oscilloscope by setting the bandwidth to 20 MHz will not do anything with the issue. The noise is still there and we see clearly that the noise is generated by the DC-DC regulator. This noise is a problem for EMC and might also affect other components negatively.

Regards,

Lars

0 Lars Roger Solem over 1 year ago in reply to Lars Roger Solem

Prodigy 170 points

We don't see any big change when adding 0.1uF cap close to the device.

Adding 10nF/0402 caps close to the IC in parallel with C200 and C201 is the most efficient solution we have found till now. But still the spikes are quite big: 200-300 mVp-p

0 Lucia Gao over 1 year ago in reply to Lars Roger Solem

TI__Mastermind 31951 points

Lars Roger Solem

Colin will get back to you during these days. Thanks!

BRs

Lucia

0 Colin Chen over 1 year ago in reply to Lars Roger Solem

TI__Mastermind 21981 points

Hi Sir,

Could you send me the layout for check?

Thanks

Colin

+1 Lars Roger Solem over 1 year ago in reply to Colin Chen

Prodigy 170 points

I think we have solved the noise issue now.

The solution is this:
- Use inductor XFL4020-222MEC

- Use 100nF/0402, 10nF/0402 and 22uF/1210 as input capacitors

- Use 10nF/0402, 10pF/0402 and 22uF/0603 as input capacitors

- Connect FSW to GND

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TPS62140: Input noise