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

Van Setten, Tim @ ACSSD tim.van.setten at acssd.L-3com.com
Thu Sep 12 03:27:35 GMT 2002


> 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.
> 
	The problem here is that injectors are inductors, and inductors in
parallel don't like to share current.  I know you see setups all the time
and in various wiring diagrams, but the correct way to wire low impedance or
peak-and-hold style injectors in parallel is to put a resistor is series
with each one.  A value of 1 to 2.2 Ohms should correct this current sharing
problem with injectors.

	The LM1949 IC is intended to run only one injector, however, the
current sense resistor can be changed to alter your "Peak" current level.
Hope this helps.....Tim.  

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