LM1949 drivers

[Sandy]

The standard LM1949 will is set for a 4/1 ratio, ie, for a 4 amp peak, 1 amp
hold style injector. This is with the 0.1 Ohm sense resistor. For 2 amp
peak, .5 hold, the value of the sense resistor should be 0.2 Ohms, and that
will do the job. The LM1949 is a slick part, and can be used for driving
ignitions as well. Look at the EFI332 FTP site for the driver board that I
designed, I think it shows using different combinations of sense resistors
and dividers to get different current limits. But remember, if the Peak and
Hold cap is used the ratio will always be 4(peak) to 1(hold).  If you need
more info, send me a mail directly 

Sandy (sganz at westworld.com)
 
At 06:19 PM 3/6/97 -0800, you wrote:
>We are on an SAE team designing an electronic fuel injection system.  We
>have completed the design and have a robust system using a Motorola 68hc11
>MCU to generate the injector pulses.  We are feeding the injector pulses
>into a National Semiconductor LM1949 injector driver.  
>Everything seems to work, ie the injectors click on and off, but on the
>oscilloscope we notice that the injectors are only taking about .9 Amps
>peak and a quarter of that on hold.  We have 2 amp peak, .5 Amp hold
>injectors from Seimans.  
>We then hooked up a 15 volt power supply directly to the injectors to see
>how much current they used with straight uncontrolled power and noticed
>that they still only had .9 Amps across them.  The same results were
>reached with two different injectors.    
>We were wondering if anyone has experience with Seimans injectors in a
>diy efi system and if there is a way to get more current through them, so
>they "peak" faster.  Thank you,
>Sean
>
>ps we're running them dry right now for test purposes, I don't know if
>that makes a difference. 
>
>