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LM5156: How can i add latch Protection?

Aditya Yedur
Prodigy 130 points
Part Number: LM5156

Hello Team 

 I am Developing Isolated DC to DC using LM5156 for below specification.

Industrial Application

Input voltage-16 to 40VDC

Output volate-5V

Output current- 3.5A

1.How should I add Latch protection in the same Circuit?

Latch protection -In case of any faults, System will re-start Only after input power is switched off and On

2. Or is there any PWM IC available with latch mode for above specification. 

Thanks

Aditya 

  • 0
    TI__Mastermind 21900 points

    Hi Aditya,

    Thanks for using the e2e forum.
    For these specs LM5156 should be a good fit.
    I am not fully sure what is meant by this latch protection.
    If the supply of the LM5156 is turned off and on again, the device will start back up with regular softstart. Is this the desired behavior, or are there any specific requirements for the restart of the device?

    Thank you very much for clarifying.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Prodigy 130 points

    Hii Niklas

    Thank you for Reply.

    Example: If Any Fault Occur (OVP, Overload, Short circuit) PWM goes in protection mode, and if any fault is not detected it will auto recover Right.

    Instead Of Auto Recover I want Latch mode.

    It Means if overload protection detects. PWM should be in protection mode only even after load get reduced. 

    After supply of the LM5156 is turned off and on again, the device will start back up with regular softstart.

    Thanks

    Aditya

  • 0 in reply to Aditya Yedur
    TI__Mastermind 21900 points

    Hi Aditya,

    Thanks for the clarification.

    Regarding OVP, Overload and Short circuit, the LM5156 device has the following features.
    OVP: If the voltage at the output is to high, the gate signal will be turned off. The device stays active and waits until the output voltage and therefore the signal at FB falls below the threshold and then starts switching again. There is no softstart here, as the device stays active the whole time.

    For overload/short circuit, the device has a cycle by cycle overcurrent protection. Once an overcurrent is detected via the CS pin, the gate will be turned off until the rest of the cycle. This happens every switching cycle until the fault disappears. Essentially, the device keeps operation, but with a strongly reduced duty cycle.
    The LM51561 device has an additional hiccup mode feature. If overcurrent is detected for 64 continuous cycles, the device will enter hiccup mode. Meaning the gate is turned off for a longer period of time and then the devices tries to ramp up with softstart again.
    A detailed description of this can be found the datasheet.

    Best regards,

    Niklas