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LM51551-Q1: LM51551

Ian Wang
Mastermind 28645 points
Part Number: LM51551-Q1

Hi Sir,

Would you pls advise 2 questions as below?

1. For Hiccup mode, check with d/s, it means overload protection.

It will calculate PWM clock cycles if >64 cycles, it will turn off switching and pulls down SS

Woud you pls kindly etail describe?

2. Standby mode looks only between start up and run mode?

If any way can enter standby mode?

3. If system want to control LM51551-Q1 by SOC.

If it mean connect as below,

When SOC pull high 3.3V > UVLO threshold 1.5V, enter run mode; pull low is shut down?

Thanks, Ian.

  • 0
    TI__Guru* 76745 points

    Hi Ian,

    To answer your questions:

    1. There is an internal counter which will count 64 events of hitting the peak current limit.  These events can have a max of 7 consecutive cycles not hitting the peak current limit.  Greater than 7 consecutive cycles of not hitting the peak limit will reset the cycle.  After the 64 events, the circuit enters the hiccup mode, which stops switching for 32k cycles, and this helps preventing the circuit from overheating in OCP.

    2. Yes.  To enter the standby mode, you need to keep the UVLO between 0.52V and 1.5V.  If UVLO is >1.5V but VCC<2.85V, it is also in the standby mode. 

    3   As mentioned int the datasheet, when UVLO pull-down for less than 35us, it is considered as the sync clock signal and the circuit will not shut down.  It only  shuts down if the UVLO is pulled down for >35us,. 

    Thanks,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    TI__Mastermind 28645 points

    Hi Youhao,

    May I send office mail to you for discuss?

    Thanks, Ian.

  • 0 in reply to Ian Wang
    TI__Guru* 76745 points

    Since we move the discussion to internal email, let me close the thread now.

    Thanks,

    Youhao