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LM5170-Q1: Nominal Circuit Breaker Function

Genius 4660 points
Part Number: LM5170-Q1
Other Parts Discussed in Thread: LM5170

In the past we got following answer for FET short check.

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the detection completes in 2~3ms.
 It only detects during startup.  After the detection, the LM5170 no longer monitors the MOSFET short until next startup.

The LM5170 only detect the MOSFET D-S short circuit condition during startup.  When VCC is ready, and UVLO is >2.5V, the LM5170 will source and sink a small current (in ~mA range) to the SW node.  If the SW voltage cannot be lifted up or pulled down, then there is a MOSFET DS short occurring.  It also source and sink the BRKG to check the breaker FETs, and do the similar check.

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Please let us know more .

There is   a small current (in ~mA range) in above description.

1.Please let us know min value of this SW current.

2.And where this current from?

3." If the SW voltage cannot be lifted up or pulled down, then there is a MOSFET DS short occurring. "

  In this case please tell me how much SW voltage and term is needed for as MOSFET DS short 

  <?mV

  >?ms

Result:High side or Low side Short

Please advise us.

Regards,

kura

  • Hi Kura,

    It is a TI proprietary IP which we cannot disclose in detail here in e2e. What we mentioned in the past, as you quoted in your post, is the basic idea behind the fault detection. Internal circuit sources and sinks a current (up to 20mA) to and from the SW node, to check whether or not the SW node voltage can be pulled up or down.  If the high side FET has D-S shorted, you will not be able to pull down the SW.  If the low side FET has D-S short, you will not be able to pull up the SW.  The SW high threshold voltage for detection is a range of 4 to 6 V, and the SW low voltage threshold for detection is less than 1V. 

    Hope this clarifies,

    Thanks,

    Youhao