Switching a N-MOSFET with Arduino Uno

I’m trying to switch a mosfet on and off using a digital pin on an arduino. I attached a schematic of my current design. The mosfet part number is CPH3457-TL-W (here’s the digikey link https://www.digikey.com/product-detail/en/on-semiconductor/CPH3457-TL-W/CPH3457-TL-WOSCT-ND/8538385). The issue is when I test it, the arduino’s output voltage seems to decrease from 5 V slowly. I’m not sure why. I’d really appreciate any help or advice.

What are you switching (what is connected to drain). Give us the whole picture.
Did you connect all grounds.
Leo..

You've wired it wemrong would he NY guess. Post schematic/wiring drawing.

This is the full schematic. VLoad is 2.5 V from a regulator. For some reason, when the arduino is plugged into the circuit, its output voltage on pin 8 decreases from 5 V. If I take the arduino out of the circuit, it returns to 5 V.

mkm8:
This is the full schematic. VLoad is 2.5 V from a regulator. For some reason, when the arduino is plugged into the circuit, its output voltage on pin 8 decreases from 5 V. If I take the arduino out of the circuit, it returns to 5 V.

What regulator? If the regulator voltage drops, it or its power source are probably being overloaded.

mkm8:
This is the full schematic. VLoad is 2.5 V from a regulator. For some reason, when the arduino is plugged into the circuit, its output voltage on pin 8 decreases from 5 V. If I take the arduino out of the circuit, it returns to 5 V.

Decreases from what to what? What is the Vcc on the Arduino while this is happening? Is the MOSFET gate voltage what you expect (ie same as pin).

Did you observe full static handling precautions with the MOSFET? That device has a gate-source voltage limit of +/-12V which is very low, so it will be particularly sensitive.

The load on pin6 of the Arduino is well within pin current specs.
Pin voltage could drop a bit from the LED current, but nothing to worry about.

As others have pointed out, what voltage is the Arduino supply if you turn on that 2.5Amp load.
(seems to be a 1ohm load on that 2.5volt supply).

Where does that current come from.
Leo..