I'm currently in the process of selecting a MOSFET transistor for an 8x8x8 LED cube I'm building. Each layer of 64 RGB LEDs will have a transistor connected to a common cathode for the layer, when I want to turn on the layer I'll turn on the MOSFET via a pin on my microcontroller running at 3.3V. This is my first time selecting a transistor for this type of application and I just want to confirm I've selected the proper part. I've used this fantastic post as a guide to help me.
I've selected the AO3400A for my application. As I'm running at 3.3V I wanted a Vgs(th) max that would be below my 3.3V level. I do have a question about the minimum value for Vgs(th) which is 650mV, I'm planning on using the Nordic NRF52832 as my microcontroller but I can't seem to find the minimum and maximum values for the logic levels in the document. Based on general reading 650mV appears to be high enough so that the gate of the transistor won't turn on when my microcontroller pin is pulled low, but I can't confirm this.
Secondly, I need to sink a lot of current through the transistor, I've assumed each LED will use a maximum of 30mA, given that I'm using RGB LEDs I have 3 x 64 LEDS in each layer. 3 x 64 x 30mA gives me 3.84 Amps of current when all the LEDS are on at once. The maximum continuous drain current is 5.7A for the transistor at 25C and 4.7A at 70C so I think I'm ok there.
I'm powering the cube with a 5V 12A supply, so the Max Vds would be 5V in my circuit and the transistor is rated for a max of 30V so again I think I'm alright.
Finally I calculated the power dissipation. P = I^2*R. I used the Rds(on) at 2.5V and 3A as a worst case scenario and that specifies a max resistance of 48mOhm. so P = 3.84A^2*48mOhm which gives me .7 Watts. The transistor is rated 1.4W at 25C and 0.9W at 70C so I figure I'm ok here as well.
Have I missed anything? Do I have enough of a safety buffer for all of my design parameters or should I select a different transistor? Thanks for taking a look!
EDIT I made a mistake in the specification of the power supply, copied some details down incorrectly when writing this. It's a 5V 12A so 60W. EDIT 2 I mistakenly put down common anode LED's instead of common cathode.