INA381: Propagation delay of comparator

1. I don't understand about max 10us of the total system overcurrent protection response time but propagation delay is only 400ns. Is this caused by slew rate? 

Yes this is caused by Slew Rate limitations.

2. Which point is the boundary between Small signal and Large signal? 

Max Slew Rate of a sine wave=2π∙F∙A.  F= Frequency A= Amplitude.  Once you have the slew rate larger of a sine wave that will dominate.  So it depends on the amplitude and the speed.

3. Slew rate limited total propagation delay, comparator and amplifier,

- What block is amplifier? Is this amp current sense amp for output?  

Yes it is the amplifier block is the analog output.

- The 2V/us Slew rate is for current sense amp not comparator. Is it right?

That is correct.  See figure 34 in datasheet for comparator transition.

4. Why Large signal propagation delay is for only comparator? On the other hand, why small signal propagation delay for comparator and amplifier? 

This is because for the amplifier the output has an input that can be a small signal and the output will respond.  The comparator will only transition from high to low and only transitions from high to low it does not change vs a small signal.  

5. Slew rate limited total propagation delay, comparator and amplifier, typ value is 3us but max is 10us. Why is there too much difference between typ. and max? Is this caused by variation slew rate? 

This could be a variety of things used in our statistics.  Customers will most likely not see that but one should design to max specifications.

6. Is there any solution to reduce the total system overcurrent protection response time less then INA381?

This I have to look into.

If you have an application note for propagation delay related to slew rate, small signal and large signal, would you please share it?

This one as well I need to look to see if we have anything for you.

Hello Javier, 

Thank you for your kind explanation. 

The customer design target of the total system overcurrent protection response time is under <1 us. please review and let me know regarding solution having lower response time or the way of reducing response time. And as I mentioned above article, If you have please share application note. 

Thanks again.

Nam,

I found this 

Saying you need a high speed amplifier and high speed comparator to get the fastest response.  Like everything there are tradeoffs.  I will ask colleagues tomorrow if they know of anything 1µs