TPS55330 noise

PhilipLee

Other Parts Discussed in Thread: TPS55330

Hi,

I use the online tool (see attached pdf) to design a 9V to 12V boost converter with TPS55330. The output of the converter is connected to a solenoid, which draws 1A when activated. When solenoid is fired, the output of the converter drops from 12V to 8V and there is oscillation every 1.3us (see attachment). I can also hear a high pitch noise while the solenoid is fired.

Where should I start to solve this issue?

Thanks,

Philip

2055.WebenchReportsServlet.pdf

over 9 years ago

0 JohnTucker over 9 years ago

TI__Guru**** 191445 points

What is the peak current when the solenoid fires? Can you measure the SW current thru the inductor?

0 PhilipLee over 9 years ago in reply to JohnTucker

Prodigy 200 points

Hi John,

I have a multimeter in series with the output of the boost converter and it measures 1A. I will try to find a current probe to measure current through the inductor.

Thanks for your help!

Philip

0 JohnTucker over 9 years ago in reply to PhilipLee

TI__Guru**** 191445 points

Yes you will need a current probe to measure any peak transients.

0 PhilipLee over 9 years ago in reply to JohnTucker

Prodigy 200 points

Hi John,

Here is the current measurement (the moment when solenoid is fired). I connect a wire to the anode of the diode D1 and use a current probe to measure current.

Thanks,

Philip

0 PhilipLee over 9 years ago in reply to PhilipLee

Prodigy 200 points

Hi John,

Is there any other measurement you need?

Thanks again for your help.

Philip

0 JohnTucker over 9 years ago in reply to PhilipLee

TI__Guru**** 191445 points

The noise in the first waveform just looks like switching noise at the nominal switching frequency of 778 kHz. If the output voltage is drooping, that usually means current limit (or possibly poor layout with high losses due to narrow traces). You sould check the switch current rather than the load current and include the SW node waveform. Also check VFB to ensure it is at 1.229V. If the output is falling that low I would expect frequency fold back to be happening though. You may also be reaching minimum on time limits as well.

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TPS55330 noise