24V with LT4295 POE

Hello,

I'm currently working on a POE powered devices with the possibility of also being powered by an auxiliary power supply.

I would like to configure the LT4295 chip to handle up to 25W at 24V (0.95A output) as can be seen on page 27 of the datasheet (https://www.analog.com/media/en/technical-documentation/data-sheets/LT4295.pdf).

This chip is also available in the current version of LTspice and I have therefore been trying to simulate the chip before implementing it on a PCB along with an auxiliary power supply (based on the LTC3777) of approximately 48V.

However, when trying to simulate the setup with only the LT4295, I encounter the problem that the output voltage is far from being at 24V.

It looks more that it goes to the 48V. The higher the load, the lower the output voltage (see screenshot).

I have put the current simulation file (only LT4295) in attachment. In this file, the aux pin is put to ground to disable the aux power path.

Could it be possible to give advice on the LTspice simulation to get a regulated 24V (+- some margin) (see zip file in attachment)?

Thank you in advance.

Laurent

 POE_LT4295.zip

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