TPS55340: TPS55340 EVM(TPS55340EVM-017) VIN noise

Lin Hsian

Expert 1580 points

Part Number: TPS55340

Hi,

Could you please why EVM board which VIN pin have noise (Due to our customer board also have this kind of noise)

Warm Regards,

Lin

over 5 years ago

0 Lin Hsian over 5 years ago

Expert 1580 points

By the way, about the waveform description:
1) Yellow: The current of VIN pin
2) Purple: The voltage of VIN pin
And the start up condition is VIN pin force 12V(connect 0.1uF cap to GND)

0 Helen chen over 5 years ago in reply to Lin Hsian

TI__Mastermind 40080 points

Dear Sir,

I can't see clear what is the voltage grade of the input voltage. Could you please upload a more clear picture?

By the way, what is the load conditions and what is the output voltage during this time, has the output voltage rise to a stable value?

0 tony tung over 5 years ago in reply to Helen chen

Prodigy 50 points

TPS55340 EVM Vin Waveform,

Vout waveforms will be supply tomorrow.

0 tony tung over 5 years ago in reply to Helen chen

Prodigy 50 points

TPS55340 EVM Vin Waveform,

Vout waveforms will be supply tomorrow.

0 Helen chen over 5 years ago in reply to tony tung

TI__Mastermind 40080 points

Dear Sir,

Hoe did you test the input voltage, did you use a very small loop across the input cap. If you directly use the probe, I'm worried the noise will directly coupled into the probe and results in poor result.

The right test way something like this:

0 tony tung over 5 years ago in reply to Helen chen

Prodigy 50 points

Dear Sir

TPS55340 EVM Vout the Waveform is as follows:

1) Yellow: The current of VIN pin

2) Purple: The voltage of VIN pin

3) Green: The Voltage of Vout Pin

0 Helen chen over 5 years ago in reply to tony tung

TI__Mastermind 40080 points

Hi Tony,

I'm pretty sure there coupled lots of noise from the switching node when testing the Vin voltage. How did you test the Vin voltage, could you please send a picture to me?

0 tony tung over 5 years ago in reply to Helen chen

Prodigy 50 points

Dear Sir,

The Vin voltage test picture is as follows:

0 Helen chen over 5 years ago in reply to tony tung

TI__Mastermind 40080 points

Dear Tony,

Thanks for the sharing. the test loop is really too big. please test this on the pcb board and just across the input cap, it will be much better.

And by the way, it seems you add an inductor before connecting the to the board, right? if so, please remove this inductor, it will introduce resonance into the circuit.