Lt4356de which application for me?

Discussion in 'General Electronics Chat' started by cdwurm, Oct 28, 2010.

  1. cdwurm

    Thread Starter New Member

    Aug 27, 2010
    4
    0
    Hello all,

    I have been having some problems with our gps tracking devices going bad in our vehicles. I noticed that all these vehicles had one thing in common, which was that they always had batteries going dead due to lack of use and sitting in the yard for too long and always having to be jump started. I did some research and read an article about jump staring and how it can cause a voltage spike for a few milliseconds that can possibly harm small electronics.

    I came across this IC from Linear
    http://cds.linear.com/docs/Datasheet/43563fa.pdf

    It gives several diffrent applications for use, I was wondering which would be the best application for us or if there is a better solution.

    Thanks
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Hello cdwurm,

    Transients are always a problem in automotive environments. Load dumps (such as when headlights are turned off; switching from high beam to low beam, etc.) can cause surges as high as 60v to occur - it's not just when jump-starting.

    Allowing an automotive battery to become discharged below ~12.5v for more than a few hours will cut the battery life short. If the battery becomes so discharged that jump-starting is required, the thin battery plates will start crumbling, and the battery will need to be replaced before very long.

    Batteries have become quite expensive. If your GPS units need more than 10mA to report their position, I suggest that they be wired so they are powered by the accessory circuit rather than directly from the battery. A 70mA load will drain an Optima battery low enough in about 10 days so that the vehicle won't start.

    Whomever is responsible for the fleet should ensure that vehicles which are idle for more than a few days should have their battery condition/charge checked. Battery maintainers are only $25-$30 each, and will keep the batteries in good shape for years.

    The LT4536 you found could be a solution; however it may be adequate to simply use a resistor in the supply path , coupled with a large ferrite toroid used as a balun and a capacitor and Zener diode to absorb the transients.
     
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