I am having an issue with the current limit at elevated temperature. I have a 12V input to 1V output. The 1V output shuts down at the following temperatures. All circuits other than this TPS40304 regulator circuit are disabled and the load is external to the chamber.
@70C - 7.864A
@85C - 5.32A
@95C - 0.511A
With 6V input @95C - 5.11A
The wave shape looks like the following at 70C and cooler.
At 95C it is as follows.
I have a 3.3V circuit that has very similar PWB layout which has the shutdown current increase at 95C. At 95C the current limit is approx. 8.1A (as expected) and it is behaving as expected.
My questions are:
What would cause the different wave shape signature?
Why would the current where shutdown occurs change so dramatically with temperature?
Things attempted.
Increased OCP setting resistor from 1.67k to 20k and then open. The 0.5A only increased to 0.85A.
Added snubber across bottom FET. Increased 95C current shutdown level to 2A.
Increased value and moved capacitors very close to IC for VDD and BP pins. No effect.
Why would the input voltage have such a dramatic effect?
Nothing other than snubber seems to have helped. I am trying to understand the cause and solution.
