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LM5146: Transient heavy load problem

Zoey Wu
Expert 5835 points
Part Number: LM5146
Other Parts Discussed in Thread: LM5141

hi team,

my customer is using LM5146 and they want to use it at heavy load and they want to avoid over current protection at application.

If I can relax the protective detection window to 4 ~ 10ms so that can support the system work, also can do DC short circuit protection
Can I add low pass to this detection window by using this capacitance in the manual diagram? The main concern is that the addition of a large capacitance in this place affects the setting of the overcurrent protection reference,

Because LM5146 has an over current protection trigger cycle of 128 cycles The current switch frequency we configure is about 500khz which makes the protection detection window much less than 1ms

  • 0
    TI__Guru 73522 points

    Hi Zoey,

    Actually, the LM5146 will detect current limit on a cycle-by-cycle basis, whereas it requires 128 cycles to engage hiccup. It's not advised to try and manipulate the timing here, as it will end up with no current limit, possibly causing a reliability issue at high current.

    If startup with high Cout is a concern, try using a high SS cap value to increase the SS time. Also, try setting the current limit at 150-160% rated full load for extra margin.

    You might also consider a peak current-mode controller where hiccup can be disabled, e.g. the LM5141.

    --

    Tim