LM74930Q1EVM: LM74930 conducts reverse current with MODE tied to VREG.

Falko Jahn

Prodigy 20 points

Part Number: LM74930Q1EVM

Tool/software:

Hi experts!

I have a strange situation with LM74930Q1EVM board.

My test system looks like this:

1. MODE is connected to VREG.

2. When Battery charger simulator is turned off, current flows from Battery simulator to Constant current load simulator. It's Ok.

3. When Battery charger simulator is turned on, current doesn't flow from it to Constant current load simulator, because of MODE pin. It's Ok.

4. Then I connect MODE pin to GND to disable RCB. Current from Battery charger simulator starts to flow to Constant current load simulator. It's Ok.

5. Then I connect back MODE pin to VREG to enable back RCB. Current from Battery charger simulator still flows to Constant current load simulator. It's NOT Ok.

One more picture to make sure that the current flows.

Any help would be appreciated!

THX!

9 months ago

0 Shiven Dhir 9 months ago

TI__Mastermind 48025 points

Hi Falko,

Thanks for the details.

Can you probe VIN, VOUT, DGATE-A, MODE signals on an oscilloscope.

Regards,

Shiven Dhir

0 Falko Jahn 9 months ago in reply to Shiven Dhir

Prodigy 20 points

Hi Shiven,

thank you very much for reply!

Here you are:

1. Vin, Vout, DGATE and MODE:

2. Vin, Vout, A and MODE:

3. And last Vin, Vout, DGATE and A a bit closer. I have implemented a small offset to be able to distinguish all four signals from each other:

I hope these will help.

Thank you!

0 Shiven Dhir 9 months ago in reply to Falko Jahn

TI__Mastermind 48025 points

Hi Faiko,

Thanks for the waveforms. Can you toggle MODE and capture the behavior.

VIN,VOUT,DGATE,MODE should be enough.

Basically, I want to see DGATE behavior during transition of MODE.

Regards,

Shiven Dhir

0 Falko Jahn 9 months ago in reply to Shiven Dhir

Prodigy 20 points

Hi Shiven,

thank you very much for a fast reply!

Here you are:

1. MODE transition from Vreg to 0V:

2. MODE transition from 0V to Vreg:

Same situation, but zoomed:

More zoomed:

Thank you very much and have a nice Weekend!

0 Shiven Dhir 9 months ago in reply to Falko Jahn

TI__Mastermind 48025 points

Hi Falko,

Thanks for the waveforms, these will help. I will get back to you be early next week. Have a nice weekend.

Regards,

Shiven Dhir

0 Shiven Dhir 9 months ago in reply to Shiven Dhir

TI__Mastermind 48025 points

Hi Falko,

Can you please help me with another set of waveforms?

Please replace VIN with "A" and VOUT with "C"

Regards,

Shiven Dhir

0 Falko Jahn 9 months ago in reply to Shiven Dhir

Prodigy 20 points

Hi Shiven,

Here you are:

Zooming..

Zooming...

Hope these will help.

THX.

0 Shiven Dhir 9 months ago in reply to Falko Jahn

TI__Mastermind 48025 points

Thanks Falko

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LM74930Q1EVM: LM74930 conducts reverse current with MODE tied to VREG.