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LM5033: Overcurrent Protection Question

Intellectual 2080 points

Replies: 1

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Part Number: LM5033

I have a customer using the LM5033/LM5107 in a similar implementation as shown in the Datasheet (Figure 11); only the system has 24V input and 12V output.

They have a test criteria that needs to be passed, where they short the 24V input to 0V for around 1ms. 

When they do this, the LM5033/LM5107 still receive their VCC supply from the bias windings, and thus are still powered during this time. This is good. The problem is, when 24V is reapplied, there is an inrush current transient that causes the LM5033 CS pin to trip, and the output is turned off.

1. Is there any workaround besides changing the input RC filter (they want to avoid a larger time constant, to keep their noise rejection bandwidth)

2. If not, they are considering the LM5030, as there is a two-stage overcurrent detection (the CS voltage has to go above 0.65V to actually shutoff the outputs). Any considerations...?

I haven't been provided with a waveform or specifics on the transient yet, but they should be coming soon.

Regards,

Darren

  • HI,

    In Fig 11 of LM5033, you can try increase R8 or C13 so to tolerate the spike if your circuit can. You also can reduce R7, change your current transformer (T2) turn ratio,  so to allow higher peak current.

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