TPS26624-25EVM: Slow response of first cycle of overload condition

Hello Venugopal,

For the first cycle, as the output had reached a voltage of 23V  and then load of 337 ohms is connected, this leads to current reaching to peak value of 66mA before current limiting.

After the first cycle there is a delay of 512ms during which the output is discharged to zero by load resistance and device starts with zero output voltage in next cycle,

For the subsequent cycles, the output has not reached input voltage (23V) and it rises with time and the peak value of current is limited to a lower value.

Hi Lokesh,

Initially I was under the impression that the output capacitor is supplying the peak current through resistor.

But the current waveform shown above was probed at the input of the Evaluation Kit (not at the load side). 

I will be expecting this current that passes through the current limiter to be limited to my set value.

Is there some kind of a delay in action of the current limiter?

Hello Venugopal,

Yes; there is a delay in current limiting. But if current exceeds  I(FASTTRIP) value, the FET is turned off with in 2us. This is described in Section 9.3.5 of the datasheet of TPS2662.

Hi Lokesh,

Thanks for your replies.

The kind of application we are having is a load that is switched on and off at speeds of upto 10 kHz. This load is to be protected from overcurrents (preferably on a cycle-by-cycle basis) . The worst load may not exceed the I(FASTTRIP) value; So the 220ns case is not useful in our case.

When the load is being switched at such high frequencies, effectively the current limiting is not operational on a cycle by cycle basis, since each cycle itself is less than this delay (1 ms, shown in the figure above). 

Do you have any better alternative parts for this application?

Hello Venugopal,

For fast current limiting for fast switching loads(10kHz), TPS1H000-Q1 or similar device might be suitable. We are looking into this and will get back in couple of days.