LM5145: Question about LM5145 ILIM Pin

Jayden Qiu

Part Number: LM5145

Hi team,

I am Jayden, I have question about LM5145 ILIM Pin. The maximum voltage between ILIM and GND is about -440mV with shunt resistor current sensing mode in my customer's application. But the absolute maximum rating of ILIM is -1V and the recommend value is 0V in datasheet. Is it ok for the application? will it affect the long-term stability of the ship?

BRS

Jayden

over 2 years ago

+1 Timothy Hegarty over 2 years ago

TI__Guru 74002 points

Hi Jayden,

Yes, no problem. Note there is no need for the RC on ILIM when using shunt current sensing. That is only for Rdson current sensing to avoid the negative spike.

Here are additional comments:

The power loss may be high with a 20mΩ shunt. Rdson sensing is lossless and is typically used for high-current (>10A) applications.
There should be no gate resistors on the low-side FET, especially the pulldown resistance as that causes Cdv/dt-induced gate spike.

Regards,

Tim

0 Jayden Qiu over 2 years ago in reply to Timothy Hegarty

TI__Intellectual 1405 points

Hi Tim,

Thanks for reply!

Will it affect when the RC is on ILIM with using shunt current sensing?

Very good comments. So, there should be no R66=2.2Ω and R69=2.2Ω on the low-side FET to minimize the effect of dv/dt induced turn-on.

Is it the same with the high-side FET? What are the requirements for the selection of FET in this situation?

Thanks.

Best Regards

Jayden

+1 Timothy Hegarty over 2 years ago in reply to Jayden Qiu

TI__Guru 74002 points

Jayden,

The high-side FET can use a boot resistor to control turn-on (then there is no need for a gate resistor, which improves the layout). The RC on ILIM shouldn't affect behavior with shunt current sensing, but you can remove the cap and use 0Ω instead.

Tim

0 Jayden Qiu over 2 years ago in reply to Timothy Hegarty

TI__Intellectual 1405 points

Hi Tim,

Thanks for strong support!

BRS

Jayden

0 Timothy Hegarty over 2 years ago in reply to Jayden Qiu

TI__Guru 74002 points

Thank you, Jayden.

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LM5145: Question about LM5145 ILIM Pin