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LTC7860 limits current if sense threshold breached?

Category: Datasheet/Specs
Product Number: LTC7860

Hi,
The LTC7860 has short circuit protection.
But the datasheet does not make clear if this is brought on by the Vout being low, or by the sense resistor voltage going above 0.09V? (or both?)

We have a 600W Power module with a LTC7860 upstream of it.
Vin is 18-36V
The LTC7860 sense resistor is 3 milliohms

The normal running current for the power module is 35Amps at 18Vin.
35A puts 0.105V across the sense resistor...thats above the sense threshold of LTC7860.

So what happens?

Does the LTC7860 start switching the PFETs or not?
Datasheet doesn't make it clear
Maybe the LTC7860 waits for the output to fall below X volts before "crying wolf " and going into short circuit protection mode?

Do you know?

Is there any circumstance at which the LTC7860 would "ignore" the sense resistor voltage going above 0.09V?

LTC7860
https://www.analog.com/en/products/ltc7860.html

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  • FormerMember
    FormerMember
+1 verified
But the datasheet does not make clear if this is brought on by the Vout being low, or by the sense resistor voltage going above 0.09V? (or both?)

It is a combination of both. When it goes over…

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  • FormerMember
    +1 FormerMember
But the datasheet does not make clear if this is brought on by the Vout being low, or by the sense resistor voltage going above 0.09V? (or both?)

It is a combination of both. When it goes over the current limit, it starts folding back the frequency to limit the current further.

Does the LTC7860 start switching the PFETs or not?

No.  You can read on pages 9 and 10 regarding how the PFETs operate.

Regards,

Jhun

  • Thnaks, so there is no situation where the current sense threshold gets breached and the LTC7860  ignores it?

    The LTC7860 would always, under any circumstances, react to a breach of the current sense threshold, and it woudl do this, by turning off the PFET? 

  • FormerMember
    0 FormerMember in reply to treez

    Yes. The foldback with ILIM setting will ensure this.

    Regards,

    Jhun

  • Reply
    • FormerMember
      0 FormerMember
    in reply to treez

    Yes. The foldback with ILIM setting will ensure this.

    Regards,

    Jhun

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