[Diy_efi] LM1949 peak-hold driver chip , bank fire 4 injectors?

Keith Ballantyne keith.ballantyne at portalplayer.com
Fri Sep 13 15:04:50 GMT 2002


I'm not convinced the 1949 will drive a mosfet properly since I think
the voltage will be limited to the 5v supply voltage, and for non
logic-level mosfets, I don't see how this will drive the gate.

Keith Ballantyne


> -----Original Message-----
> From: Tony Bryant [mailto:brd at paradise.net.nz]
> Sent: Tuesday, September 10, 2002 8:24 PM
> To: diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] LM1949 peak-hold driver chip , bank fire 4
> injectors?
>=20
> On Wed, 11 Sep 2002 06:51, Les Dittert wrote:
> > The national LM1949 is made to drive a transistor to fire an
> > injector peak and hold style. Can someone tell me to tell me if
> > it's possible to use this with a bank firing of 4  injectors?
> > My concern is the selection of the proper transistor (can it be a
> > mosfet)
> > and also the overloading of the zenor diode, since it's getting back
> > current
> >  from 4 injectors instead of one.
>=20
> I think its fine, if the injectors are of similar inductance, since
the
> current in the peak phase through will ramp up independantly and a
rate
> inversely proportional to the inductance
>=20
> The zener takes the whole of the energy stored into the inductors, so
size
> it
> using:
>=20
> E=3D (LI^2)/2
> Pzener=3D fmax(LI^2)/2
>=20
> The mosfet passes the average current:
>=20
> Pmosfet=3D(Iavg^2)Rds
>=20
> Iavg ~=3D~ Ihold * Duty
>=20
> The stablility of the hold feedback loop is up for question though -
any
> body?
>=20
>=20
> _______________________________________________
> Diy_efi mailing list
> Diy_efi at diy-efi.org
> http://www.diy-efi.org/mailman/listinfo/diy_efi

_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi



More information about the Diy_efi mailing list