Injectors and resistors (and i'm back)

[Wen Yen Chan]

The LM1949 is available from Newark electonics.

Wen

On Tue, 24 Nov 1998, Sandy wrote:

> You don't need to waste the extra $$ on the FET drive, a TIP121 or better
> (about 50 cents) will work great for peak and hold with that circuit. The
> Flyback zener voltage is dependant on the decay time required for the
> circuit, and that's why they just don't use a diode. I have used 33volt
> zeners, and also tested with the easier to get Transient Voltage
> Suppressors (TVS, like 1.5k33CA) that are easier to get in 5 watt ranges
> from Digikey or Mouser. Both work great. Besure to heatsink the
> transistor/FET when using Peak and Hold injectors, and lastly if you do
> drive a FET or a IGBT, you will have to check the circuit for oscillations,
> as I have built the driver with IGBT's and had to add a small capicator to
> the Base of the IGBT to keep it stable.
> 
> Sandy
> 
> At 08:50 AM 11/24/98 -0600, you wrote:
> >
> >> > What about EMI when you shut off the inductive load... use the body
> diode of
> >> > the FET to catch the spike?... if so what voltage?  How about an RC
> snubber
> >> > across the injector... or is EMI not a problem (maybe inductance is low?)
> >> 
> >> Check out the schematics for using the Nat'l Semi LM1949 Inj Driver
> >> Cntrlr. It's a PDF file available from www.nsc.com. It uses a 50V zener,
> >> AIR..this for driving the std 4-1 peak and hold injector..ala GM TBI.
> >
> >They say you're losing your mind when you reply to yourself, but
> >just to be clear...the spike is clipped by a 33v 5watt zener per
> >LM1949 datasheet.                            **
> >
> >-greg
> > 
>