Post by thread:power MOSFET that can be switched by PIC

>Can anyone recommend a readily available power MOSFET with low on >resistance (<0.03 ohm) when directly driven from a PIC output (5 volt >supply). I ordered what looked like a promising device from Digi-key, >only to find out that it was "vapor-ware". Current capacity required >is modest, but must have low Ron. Thanks > >jk If you can get +12V somewhere you can switch MOSFETS with the PIC. Just connect the PIC output pin to the MOSFET gate and pull the gate to 12V with a 10k or so resistor, larger means slower response when turning on. You may want to put a small, 500 ohms or so, between the PIC and MOSFET gate. This is to limit the short current spikes that may occur when discharging the gate capacitance of the MOSFET. Now you can turn the MOSFET on my making the PIC pin an INPUT, this should put the pin into a high impedance state, letting the MOSFET gate be pulled high by the 10k resistor. To turn the MOSFET off, just make the pin an output and drive it low, pulling the MOSFET gate to ground. Hope this help, -shane ------------------------------------------------------------------------- Shane Trent Diamond Deposition and Analysis Laboratory NCSU Box 7919 Internet: spam_OUTsdtrentTakeThisOuTmte.ncsu.edu 1001 Capability Drive Voice: (919) 515-7083 Raleigh, NC 27695-7919 Fax: (919) 515-6037 -------------------------------------------------------------------------

On Sun, 5 Feb 1995 Shane Trent <.....sdtrentKILLspam@spam@MAT.MTE.NCSU.EDU> said: >>Can anyone recommend a readily available power MOSFET with low on >>resistance (<0.03 ohm) when directly driven from a PIC output (5 volt >>supply). I ordered what looked like a promising device from Digi-key, >>only to find out that it was "vapor-ware". Current capacity required >>is modest, but must have low Ron. Thanks >> >>jk > >If you can get +12V somewhere you can switch MOSFETS with the PIC. Just >connect the PIC output pin to the MOSFET gate and pull the gate to 12V with a >10k or so resistor, larger means slower response when turning on. You may want >to put a small, 500 ohms or so, between the PIC and MOSFET gate. This is to >limit the short current spikes that may occur when discharging the gate >capacitance of the MOSFET. Now you can turn the MOSFET on my making the PIC >pin an INPUT, this should put the pin into a high impedance state, letting the >MOSFET gate be pulled high by the 10k resistor. To turn the MOSFET off, just >make the pin an output and drive it low, pulling the MOSFET gate to ground. > >Hope this help, >-shane You might have a problem with this. Every i/o pin on a pic has protection diodes to both VSS and VDD. This limits the pin voltage to about 5.6 volts (if vdd=5v). I suppose you could get around this with yet another diode, but now it's getting a bit more complicated then the original request. later ....... carl Henry Carl Ott N2RVQ carlKILLspampipeline.com ------------------------------------------------ No wife, no horse, no spell checker. ------------------------------------------------

"John S. Kallend" <.....METMKALLENDKILLspam.....MINNA.ACC.IIT.EDU> wrote on >Subject: power MOSFET that can be switched by PIC > >Can anyone recommend a readily available power MOSFET with low on >resistance (<0.03 ohm) when directly driven from a PIC output (5 volt >supply). I ordered what looked like a promising device from Digi-key, >only to find out that it was "vapor-ware". Current capacity required >is modest, but must have low Ron. Thanks Hi John, Harris makes N-Channel Logic Level Power FETs (MegaFETs). Their device RFP50N05L has rDS(ON)= 0.027 Ohms at VGS=4V. Is that short enough for your circuit? Kind regards, Volkmar --- Volkmar Gross, Softwork Telematica, Bremen, Germany (Fone&Phax: +49 421 74434) >>>----------------------------------------------------------------------------- > Planck's quantum is the calorimetric equivalent of a Baud (Max Demon)