TPS61193: Ringing between two clock cycle.

Balakrishnan K

Part Number: TPS61193

Hello,

We are using TPS61193 part in one of design for Gauge illumination back light section.

FSET = 28.7K , which is 1.9MHz, while measuring at SW pin observing some ringing between the clock cycle (highlighted with Cursor) at operating VIN = 10V to 13.5V

At VIN is 6V-9V & 14V to 18V, not observing any ringing , waveform looks stable between the clock cycle

Note: Clock cycle are not continuous. Please see below waveforms and schematic page.

Why is this kind of behavior observing with different voltage. Please help us.

After adding the Snubber Circuit - Ringing section changing.

Schematic is attached:

Thanks and Regards

Balakrishnan

over 6 years ago

0 Kenneth Du over 6 years ago

TI__Genius 14295 points

Hi, Balakrishnan,

Proper engineer has been assigned to take a look at this and will reply you next week.

0 Sean Zhou over 6 years ago

TI__Mastermind 22745 points

Hi Balakrishnan K,
That's because the circuit works under Pulse Skip Mode, the ring is between the inductor and capacitor of MOSFET。That's the normal phenomenon. What's you load condition when you test the SW waveform? Full load or no load?
Regards
Sean

0 Balakrishnan K over 6 years ago in reply to Sean Zhou

Prodigy 50 points

Hi Sean,

Thank you for response, Its with full load condition.

Is possible to arrest the ring with external component, I couldn't find online simulation for TPS61193 IC in switch pro and TI site.

Please suggest best possible way to sort out.

Regards
Balakrishnan

0 Sean Zhou over 6 years ago in reply to Balakrishnan K

TI__Mastermind 22745 points

Hi Balakrishnan,
Adding the snubber circuit is a good way, And I suggest you to decrease the switching frequency to test again. And please optimize the PCB layout to optimize the rining.
Regards
Sean

0 Balakrishnan K over 6 years ago in reply to Sean Zhou

Prodigy 50 points

Hi Sean,

I added the snubber circuit R=56ohm & C=6.8nF, And ring is changed to below mentioned waveform.

Is this accepted behavior ?. This low drop kind signal wont create any issue in Conduction and Radiated emission.

We followed the layout guidelines from TPS61193 datasheet. Do you have any additional layout and design guide for TPS61193 better optimization

Thanks and Regards

Balakrishnan

0 Sean Zhou over 6 years ago in reply to Balakrishnan K

TI__Mastermind 22745 points

Hi Balahrishnan,
Yes, this is a common solution for high switching noise on SW point. I don't have much more commons on this. If you found new question, please let me know.
Reagrds
Sean

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TPS61193: Ringing between two clock cycle.