LM74700: Design help. Ringing in Gate

Marvn Arcangel

Part Number: LM747

Hi Team,

A customer using the LM747 and is facing an issue where they have seen ringing on the gate signal. what could be the reason of this? can you share information about how to improve this?

Below is the screenshot of the schematic and the gate signal captured.

Thank you in advance.

Regards,

Marvin

over 3 years ago

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Marvin,

ok, you mean the LM74700 and not the LM747?

Kai

0 Ron Michallick over 3 years ago in reply to kai klaas69

TI__Guru**** 174096 points

Hello Marvin,

I transferred post to LM74700 support.

0 Marvn Arcangel over 3 years ago in reply to Ron Michallick

TI__Genius 16420 points

Hi Ron and Kai,

Thank you. Yes this is for LM74700. Sorry for the confusion.

Looking forward to your response.

Regards,

Marvin

0 Marvn Arcangel over 3 years ago in reply to Marvn Arcangel

TI__Genius 16420 points

Hi Team,

Any update?

Regards,

Marvin

+1 Praveen GD over 3 years ago in reply to Marvn Arcangel

TI__Guru 57737 points

Hi Marvin,

Please refer to the below e2e FAQ's to understand the reason behind your observations on LM74700-Q1 gate signal:

Ideal Diode Controller or Linear ORing Controller Gate voltage oscillates at light load or no load

https://e2e.ti.com/support/power-management/f/power-management-forum/992989/faq-ideal-diode-controller-or-linear-oring-controller-gate-voltage-oscillates-at-light-load-or-no-load

Ideal Diode Controller or ORing Controller gate voltage is lower than expected

https://e2e.ti.com/support/power-management/f/power-management-forum/994546/faq-lm74700-q1-ideal-diode-controller-or-oring-controller-gate-voltage-is-lower-than-expected

0 PRAHLAD Supeda over 3 years ago in reply to Praveen GD

TI__Expert 6220 points

Hi Praveen,

After connecting 1.8amp load also customer could see ringing on the gate. As load will be vary so minimum load is 200mA to 15A. Any recommendations from your side?

0 kai klaas69 over 3 years ago in reply to PRAHLAD Supeda

Guru 140200 points

Hi Prahlad,

have you tried the countermeasures given by Praveen?

Why is the ringing on the gate an issue for you?

Kai

0 Dinesh Gread2 over 3 years ago in reply to kai klaas69

Intellectual 360 points

Hello ,

I have tried all the suggestion even a resistive load of 1.8 Amp still i could see the ringing on the gate,

why it is issue because i am not able to get the clean waveform of the voltage on the output due to this high ringing on the fare as the Pk-pk ripple is vary high at teh out . it is traveling from 14.3 to 15V in a very very high frequency .

0 Praveen GD over 3 years ago in reply to Dinesh Gread2

TI__Guru 57737 points

HI Dinesh,

What is the total output capacitance -? Please share the complete schematics of LM74700-Q1.

What is the power source at the input ? - Is it a battery or a DC-DC converter?

Please share waveform capture with Vin, Vout, GATE and VCAP signals captured at 1.8A load.

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LM74700: Design help. Ringing in Gate