I designed a board which uses the LTC7003 and an N-channel MOSFET to control a power output. I have set the current limit to approximately 3.23 A by using a 0.007 Ohm current sense resistor and a 45.3 kOhm resistor on the ISET pin. There is a 0.33 uF capacitor on the TIMER pin which should give a 4.6 ms fault time. I am finding that the LTC7003 does not detect an overcurrent fault even with the output load set to over 4 Amps.
I have used this LTC7003 design on a previous board and it functioned properly. The biggest difference between these two boards is that the new board design uses a different regulator to power the PYLD_PWR net and I have seen that this net is quite electrically noisy, with about 90 mV ripple on the nominal 28 VDC signal and much larger peaks due to switching noise. Could the additional noise be causing issues in the LTC7003?
I have probed the ISET and IMON pins while a 4 A load was present and saw that the voltage at IMON was greater than the voltage at ISET, indicating that the LTC7003 does see that the load current is greater than the threshold. However, the voltage on the TIMER pin remains at 0 V. I have verified that there is not a short from the TIMER pin to ground or any adjacent pins.
I have attached a screenshot of the schematic. Does anybody have any ideas of why the LTC7003 is not detecting an overcurrent fault? I have tried populating the filter capacitor between SNS+ and SNS- pins but saw no effect on the behavior.