I'm trying to find out if my mosfet needs a heat sink. my load draw 1.20 A and im triggering the mosfet with ardino pin 7 5V

P= current squared * RDS
1.20 A * .16 Ohms squared = .2302

TJmax - Tambient / ROJA
150 - 25 / 62 = 2.02

2.02 is larger then .2302 so I need a heat sink

 

How is your load V/I, do you have a circuit?
You can choosing some other mosfets has lower Rds then it could reducing the power consumption.

 

2.02 is larger then .2302 so I need a heat sink

No, you don't. MOSFET is o'k up to 2W w/o heatsink, and it's needs to dissipate 0.23W. Are you using PWM? Losses may be more in case PWM

 

No, you don't. MOSFET is o'k up to 2W w/o heatsink, and it's needs to dissipate 0.23W. Are you using PWM? Losses may be more in case PWM

No I'm not. And thank you!

 

I'm trying to find out if my mosfet needs a heat sink. my load draw 1.20 A and im triggering the mosfet with ardino pin 7 5V

P= current squared * RDS
1.20 A * .16 Ohms squared = .2302

TJmax - Tambient / ROJA
150 - 25 / 62 = 2.02

2.02 is larger then .2302 so I need a heat sink

Note that
150 - 25 / 62 = 149.60

Remember order of operations!

If you mean (150 - 25) / 62, then say so.

Also, use your units and your answer becomes much more informative:

Pmax = (TJmax - Tambient)/ROJA = (150 °C - 25 °C)/(62 °C/W) = 2.02 W

Pactual = I²·Rds = (1.2 A)²·(0.16 Ω) = 0.23 W

Since Pactual < Pmax, no heat sink needed.

 

Rds=0.16 ohm is usually normalized (room temperature). If you operate at Tj=150°C we would have Rds=2.2*0.16=0.35ohm (see Fig.4 in the datasheet).