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LMR54406: Overload current point

Shaofeng Luo
Intellectual 1540 points
Part Number: LMR54406

Hi experts

For LMR54406, we notice that Isc is quite high, 1.1A typ. If we use this device in 12V to 5V application, with 15uH inductor, LMR54406 will still works at 1A load and no OCP. And it will overheat and shutdown with OTP finally.

It brings troubles to customers since it may bring thermal damage to the materials around this device.

I'm suggesting to decrease the inductance to 6.8uH or even 4.7uH, with larger Cap to guarantee the Vout ripple. It may work since the IL ripple is larger and it will trigger OCP at maybe 0.8A. Do you agree with this? Or do you have any insights? Thanks!

  • 0
    TI__Guru 72745 points

    Hi Shaofeng,

    Thank you for posting.  Are you talking about a real problem that the customer has already seen, or just a worry of something imaginary that may happen?  Note that the Isc threshold is introduced to protect the IC under output short, and the imaginary thermal damage seems to be an over concern.  Note that the circuit enters the hiccup mode in short circuit condition to allow cooling down. 

    Since the loop compensation is internally fixed, reducing the inductor to be much less than the recommended value (Eq. 9 or Table 8-1), may lead to instability. 

    Thanks,

    Youhao