LM5143-Q1: Output abnormal Vin=15V@Vout=14V

Andy Jin

Part Number: LM5143-Q1
Other Parts Discussed in Thread: LM5143

Tool/software:

Hi expert,

Our project used the TI LM5143 chip, and during the debugging process, we encountered a problem. We have one power output set to 14V, and the schematic is attached. During the rise of the input power supply voltage, an abnormal output waveform is observed, exhibiting oscillations. When the input power is at 11V, the output is normal, and the waveforms of the upper and lower MOSFETs are shown in the figure below: yellow for the upper MOSFET and blue for the lower MOSFET.

When the power input is 15V, the output is abnormal. Under no load, the inductor heats up, and the output waveform is abnormal, as shown in the figure below.

Thanks a lot!

Andy72241.Schematic.pdf

27 days ago

0 Onkar Bhakare 27 days ago

TI__Genius 10916 points

Hello Andy

Kindly share waveforms at following nodes to aid the debug

SW
Vout
COMP

Additionally, share fill Quickstart to understand the design better. You can find it here - LM5143DESIGN-CALC Calculation tool | TI.com

Thank you

Regards

Onkar Bhakare

0 Andy Jin 27 days ago in reply to Onkar Bhakare

Intellectual 410 points

HI Onkar,

By change the resistor on Mode pin from 0ohm to 10k, the performance is improved.

Add the waveform.

1) Normal SW(Yellow), Vout(Blue) under low voltage input.

The COMP waveform:

2) The waveform of the high-voltage oscillation is as follows: yellow SW, blue VOUT.

The COMP waveform

Thanks a lot!

Andy

0 Onkar Bhakare 27 days ago in reply to Andy Jin

TI__Genius 10916 points

Hello Andy

Thanks for sharing those waveforms. Could you please share quickstart as well?

Thank you

Regards

Onkar Bhakare

0 Andy Jin 27 days ago in reply to Onkar Bhakare

Intellectual 410 points

Hi Onkar,

The design parameter is as below:

1) Input voltage: 9V~16V

2) Output1: 14V@10A,

3) Output2: 5V@10A

When the input voltage is below 14V, the output voltage is equal to the input voltage.

Thanks a lot!

Andy

0 Onkar Bhakare 24 days ago in reply to Andy Jin

TI__Genius 10916 points

Hello Andy

Error amplifier's Gm reduces by connecting mode by 10k to AGND. If you are seeing improvement by doing this, it suggests there could be scope for improvement in compensation network. Could please share filled calculator for review?

Thank you

Regards

Onkar Bhakare

0 Onkar Bhakare 17 days ago in reply to Onkar Bhakare

TI__Genius 10916 points

Hello Andy

Any updates on this?

Thank you

Regards

Onkar Bhakare

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LM5143-Q1: Output abnormal Vin=15V@Vout=14V