It's Roy here. I'm currently working on a project where I need UVLO to keep my both POE++ power supplies operate the same time in series connection (They are identical btw). Each power supply offer 12vdc and a combined 24 Vdc to the load. The LTC4365 circuit I used set UV=23V, OV=25V, and it's working fine without a load. However, when a load is connected, it's not working as desired. The dummy load I designed is using an op-amp generating 5khz PWM to control the voltage added to the load (And the dummy load works fine when connected to the single power supply). The voltage therefore should have the same frequency of 5khz. However, when using the LTC4365, the frequency drops to 25 or 35hz only, which is weird. And the POE PD I used is designed to work under high frequency, and it shut itself down under low frequency when I increase the duty cycle of the load. Do you have any insight regarding this? Thank you for your help in advance.