From: nospam@no-address.com   
      
   On 2018-08-19 22:13, whit3rd wrote:   
   > On Wednesday, August 15, 2018 at 7:41:03 AM UTC-7, Cursitor Doom   
   > wrote:   
   >> On Mon, 13 Aug 2018 13:40:56 -0400, Bob Engelhardt wrote:   
   >>   
   >>> I have a Milwaukee 12v variable speed tool with a bad control   
   >>> board. Rather than replace the board, I'm planning to just use   
   >>> ... a MOSFET   
   >   
   >> If it's an inductive load you'll want a back EMF protection diode   
   >> across it as well; save blowing your MOSFET.   
   >   
   > That's not necessary; every power MOSFET has a parasitic drain-source   
   > diode already.   
      
   That does not protect the MOSFET from inductive kickback that raises   
   D over VDD. The internal diode only clamps D from going below S.   
      
   So, the some means of protection is still necessary, be it either a   
   diode from D to VDD or a TVS (or Zener) from D to S.   
      
   The later may be more reliable as the TVS can be placed close to the   
   MOSFET and this avoids the inductance of the wiring to the battery.   
      
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