[Diy_efi] Re: injector current-feedback driver

bcroe at juno.com bcroe at juno.com
Tue Mar 4 00:02:45 GMT 2003


If you want to drive an FET with 5 volt HC logic, you 
ought to use a LOGIC level input FET.  Trying to drive 
the generic 4 volt threshold FET with 5 volt logic really 
doesn't do the job.  

In addition, some current is required during the state 
transitions, so I use an AC chip for driving repetitive or 
time critical apps.  Just insert the AC after your HC, OK 
to parallel sections for more drive.  I insert a series 
resistor to limit gate drive current to 24ma per section, 
if its too slow that way, try a full blown FET driver chip or 
possibly an FET with less input capacity.

Bruce Roe

3 Mar 2003 Lasse Langwadt Christensen <langwadt at ieee.org> writes:
> Marcell Gal wrote:
> > Hi Mark,
> > 
> big snip
> > 
> > What if Q1 is a darlington?
> > What FET do you recommend for max 6A? Do I need a FET-drive
> > than (like megasquirt) or 5 Volt HC output is fine for
> > driving FET gate?
> > thanx:
> > Marcell
> 
> I friend of mine has been using buk108-50 for saturated
> injectors with the gate driven directly from a 5volt cpu.
> 
> it has buildin over-current and temperature protection, and
> overvoltage clamping at around 50volts so it doesn't need
> any external clamping(1)
> 
> -Lasse

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