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I have an application where I want to switch on/off a resistive load (24V/300mA) from a 3.3V MCU GPIO pin at a rate of 1 HZ or slower. I also have some IRL2703 MOSFETs, and I wonder if they would do the job. Or generally, how to read a MOSFET datasheet to find out if it would do the job.

Looking at the datasheet, I find/interpret

  1. Drain-to-Source Breakdown Voltage 30V -> sufficient for the to-be-switched 24V

  2. RDS(on) only specified down to Vgs = 4.5V, so it does not tell me about my 3.3V.

  3. For completeness, the Gate Threshold Voltage is min. 1V (no typ. or max. value listed), but that does not tell me if 3.3 V will work correctly.

  4. Fig. 1 "Typical Output Characteristics" shows Id = 2A @ Vds = 24V @ Vgs = 3.0V @ Tj = 25 °C @ 20 us pulse-width

  5. Fig. 2 "Typical Output Characteristics" shows Id = 4A @ Vds = 24V @ Vgs = 3.0V @ Tj = 175 °C @ 20 us pulse-width

I'm assuming that 20 us pulse-width refers to a PWM signal with 20 us HIGH and 20 us LOW, i.e. 50% duty cycle. Because I want to drive the MOSFET steadily, I guess that I can only drive half of Id, i.e. Id = 1A @ Tj = 25 °C.

Is my understanding correct? The graphs are typical characteristics. How do I obtain the minimum guaranteed/worst case Id?

How can I estimate the RDS(On) (and thus the dissipated power) in my setting?

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  • \$\begingroup\$ I have tried the circuit as described above and it seems to work. But I still would like to know if I'm on the safe side, i.e. within specifications or just lucky. \$\endgroup\$ – matge Nov 25 '18 at 23:45

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