LM74800EVM-CD: LM74800QDRRRQ1 circuit operation

Leo H

Part Number: LM74800EVM-CD

Tool/software:

I have set the LM74800 controller to enable when PS_12Vout ~ 10.5V.
I am seeing Q10 source voltage oscillating between 8-10.5V when U21 enabled even under 10-20A load.
Is this expected? Shouldnt Q10 be fully enabled during moderate loading condition?

4 months ago

0 Shiven Dhir 4 months ago

TI__Mastermind 47440 points

Hi Leo,

Can you share some waveforms of this scenario.

Please check if the FET is damaged or not.

Also, try loading the system after HGATE is fully high.

Regards,

Shiven Dhir

0 Leo H 4 months ago in reply to Shiven Dhir

Prodigy 165 points

Can share shortly.
Once I increase the enable threshold to 11.5V there is no jitter/oscillation even under low load i.e. Q10 VGS stable. Do you know why that is?

0 Shiven Dhir 4 months ago in reply to Leo H

TI__Mastermind 47440 points

Hi Leo,

There is a chance that VS in unstable.

Regards,

Shiven Dhir

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LM74800EVM-CD: LM74800QDRRRQ1 circuit operation