This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM5170-Q1: failure detection of LM5170

Part Number: LM5170-Q1
Other Parts Discussed in Thread: LM5170, TIDA-01168

Hello.

Please tell me about the failure detection of LM5170.

Used in 4-phase buck converter (48V-> 14V).

The circuit diagram is TIDA-01168.

Connecting a 10k resistor to SYNCOUT will work fine.
MOS is not damaged.
However, it will not work if you remove the 10k resistor.
After checking the waveform, nFAULT goes high for about 3 milliseconds at startup,It will be lower soon.
Even if UVLO changes from HI to LOW to HI, nFAULT simply repeats the above.
Are you using it incorrectly?


Thank you.

  • Hi Ksma,

    Thank you for considering the LM5170.  The failure detection is disabled for TIDA-01168 because there are large capacitors between the current sense resistor and the 12V-sider breaker FETs. The circuit checks the MOSFET failure by an small current to pull up and down the SW nodes.  If there is large capacitor between the SW and the 12V breaker FETs, you will not be able to pull up or down the SW node in the time frame allowed for failure detection (2~3ms).  So, you should always install the 10k resistor at the SYNCOUT pin to avoid the conflict, otherwise the IC "thinks" there is a MOSFET failure.

    Thanks,

    Youhao Xi, Applications Engineering.  

  • Hello Youhao,

    Thank you for your answer.
    Please tell me a little more.
    We want to enable this feature.
    I think the countermeasure is to reduce the capacity of the smoothing capacitor,
    Is there a maximum capacity?
    Thanks,
    Ksma
  • Hi Ksma,

    The max capacitance is 1uF, to avoid causing false failure detection. 

    Thanks,m

    Youhao