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I am using the MIC5060 High Side gate driver (576-3669-1-ND) to control N-channel MOSFETs with an Rds(on) of about 0.8 mOhm. I want to use this particular MOSFET for high-side reverse polarity protection up to -30 V.
I tried to connect a diode between the positive supply (tied to the input) and was disappointed to see the chip get fried around -20 V.
I read that in this scenario there exist Ideal Diode Controllers which can withstand much higher reverse voltages and get the job done, but they regulate the Vds of the FET to 20 mV or so, which would increase the power loss across the FET by a factor of 5.
Is there any way I could add components to still use this driver and maintain high efficiency while also being reverse polarity protected to -30 V?
Here it the schematic of the blocking portion of the circuit. “Post Blocking FET” is the net that powers the rest of the board.
To test it I reversed the +12V and GND connections to the screw terminal, I found that it was OK at low voltages but I wanted to increase beyond -20 V.
The absolute maximum for the Microchip MIC5060’s source input is -20 VDC. This hard limit seems to be supported by your experiment.
The schematic has an atypical right to left flow. As I understand, the current is flowing from “Post Blocking FET” to the -12 section. The damage occurs when a voltage less than -20 VDC is injected onto the 12 VDC screw terminals.
It’s possible that moving the source input to the diode (pin 2 and 3 now tied together) would solve the problem. However, I fear this is a setup for circuit oscillation.
Sorry, I don’t have a better solution. The best I can offer is a brute force protection against the negative transients using resistor Zener clamps.
Sincerely,
Aaron
P.S. What is the current limiting mechanism when the -12 VDC is forced to -20 VDC?
Although the MIC5060 is probably not intended to be used as an ideal diode driver, I think your circuit is novel. However, the data sheet does not say too much about that reverse battery condition, especially how it is ensured that the Q1 gate is shunted to source in the reverse battery condition (could assume here that it is done through the ESD diodes or something. The “functional block diagram” on the datasheet does not offer much help).
In order to extend the reverse condition up to -30V, you’ll need to isolate the MIC5060 and have an external circuitry to ensure that the gate of Q1 is shunted to source in order to keep the FET OFF-state. As AP hinted, the chip’s SOURCE pin should go behind the protective diode D11, but the GATE pin is a bit more complex case.
