I have a project with the following requirements:
* "Discrete Output" with high impedance in the OFF state and approximately 100 Ohms to ground in the ON state
* Maximum voltage on the "output" pin of 32.2V
* Withstand lightning waveforms of 600V and 300V in both polarities
* Very small enclosure which limits high wattage part options
* No high speed switching requirements
* High vibration environment (no relays)
I originally envisioned the attached circuit. There are two 50-Ohm 1W wire wound resistors to split the lightning event voltage for the TVS diode. The ON and OFF states would be controlled through a MOSFET with a 5V gate driver.
This circuit can handle the specific lightning events I am targeting, but the problem is the potentially continuous 32.2V applied to the output. When the MOSFET is ON, this would sink about 322mA. Each resistor would require 5W+ each. This is a small enclosure with space for only surface mount parts. I could handle about 1W wire-wound resistors max. The transistor must also be very small.
I'm at a loss for other solutions with these requirements. Am I missing something or is there a better method for this type of function?
* "Discrete Output" with high impedance in the OFF state and approximately 100 Ohms to ground in the ON state
* Maximum voltage on the "output" pin of 32.2V
* Withstand lightning waveforms of 600V and 300V in both polarities
* Very small enclosure which limits high wattage part options
* No high speed switching requirements
* High vibration environment (no relays)
I originally envisioned the attached circuit. There are two 50-Ohm 1W wire wound resistors to split the lightning event voltage for the TVS diode. The ON and OFF states would be controlled through a MOSFET with a 5V gate driver.
This circuit can handle the specific lightning events I am targeting, but the problem is the potentially continuous 32.2V applied to the output. When the MOSFET is ON, this would sink about 322mA. Each resistor would require 5W+ each. This is a small enclosure with space for only surface mount parts. I could handle about 1W wire-wound resistors max. The transistor must also be very small.
I'm at a loss for other solutions with these requirements. Am I missing something or is there a better method for this type of function?
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