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I'm creating a circuit using two FETs. The first FET (U2A) is responsible for controlling the inrush current of the solenoid, and the second one (U2B) is used to maintain the predetermined hold current. Initially, I considered using two GPIO pins on the controller to control this, but due to a GPIO deficiency on the board and the need to control 8 solenoids, I decided to use only one controller GPIO pin. When the GPIO signal is high, it should activate both FETs. After a delay of 200ms to 100ms, the inrush FET should be deactivated, while the hold FET continues to provide the constant predefined hold current unless the GPIO signal goes low. The goal is to reduce the current supplied to the solenoid to prevent overheating issues. I could go with PWM-based solutions, but the problem with that is switching at 24 volts creates switching noise in the circuit, affecting the other components on the board.

The problems with my circuit are as follows:

(i) R3 is 1 Mega Ohm, and this can create a delay of 500ms in simulations, but in reality, it may not be able to drop the voltage below the Vg threshold to turn it off since the base current of the transistor is too low.

(ii) Any optimized circuitry with fewer components, except PWM, would be preferable. The entire circuit can also be changed to achieve the required goals.

(iii) My main concerns are with the inrush current delay circuitry, which can also be modified if changes in any components could result in achieving better performance. The hold current circuitry should work well

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    \$\begingroup\$ What kind of DC solenoid is this that exhibits inrush? Please show supporting information, device characteristics, waveforms, etc. What is your exact GPIO situation, how many pins are available, what types, and how many channels are required (ok, about 8)? Would expanders be acceptable? How about a solenoid driver array? Why is switching a problem, what in your circuit is being interfered with? What is your layout like? What if you add an LC filter before the solenoid? Consider these questions first; avoid asking an X-Y question. \$\endgroup\$ Oct 2, 2023 at 14:59

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I could go with PWM-based solutions, but the problem with that is switching at 24 volts creates switching noise in the circuit, affecting the other components on the board.

Then your "board" is badly designed. I mean, what happens with switching converters operating in the tens of kW region at hundreds of volts and amps? How do you think they cope.

Anyway, you don't need two MOSFETs because this can all be done with PWM using one MOSFET.

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