| Electronics > Projects, Designs, and Technical Stuff |
| Why is this MOSFET here? |
| (1/2) > >> |
| Gelf54:
I've just fixed my old Dell C600 laptop (after our cat decided to mark it as his own, which corroded away some IC pins) and noticed in the circuit diagrams this MOSFET circuit. I've seen similar before and haven't figured out why it's used. It can't be providing reverse voltage protection, since the body diode only has a Vsd of around 0.7V, and it can't be providing under-voltage lockout, since the Vgs threshold is only around 1.7V. Thoughts? [Edit] Never mind, I think I just figured it out. The 33K & 100K resistors do provide an under-voltage lockout of around 7V I'd estimate. Not sure why this is necessary. The battery is around 14.8VDC. Guess it prevents spurious logic signals before the +5V & +3.3V rails have stabilised, or during power down. |
| Gelf54:
Because of the MOSFET body diode. |
| Zero999:
Are you sure it's drawn correctly? |
| Gelf54:
I have no reason to think otherwise atm. Is there a slightly different circuit that you have in mind? |
| JackJones:
It looks like a soft start circuit rather than polarity protection. |
| Navigation |
| Message Index |
| Next page |