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Application and circuit design for TL7715A

Hans Achter
Prodigy 20 points
Other Parts Discussed in Thread: TL7715A, TPS3700, TPS3701

Hello all,

I have an application where I want to use the TL7715A and was hoping for some guidance.

The application is automotive, I want to monitor and take action based on the charging voltage from an alternator.   The 13.5 volt trigger point is about where I want to be since the voltage is usually above 14 when charging properly and below 13 when not charging. 

I want to basically do the operation of a SPDT relay onto another separate circuit:  if voltage less than 13.5 volts, apply the battery ground ;  if voltage higher than 13.5 volts then apply the voltage output from the alternator.

I'm great at a lot of things but oddly slow with electronics, so I need a lot of hand-holding...   I think that I can use each RESET pin to apply each of the two SPDT conditions?  I was thinking to use a transistor on each RESET pin, like a 2N5551?  The current needs are pretty low, just run a couple of relays at most, so the 600 mA capacity of that transistor should be fine.  If my thinking is correct there, could someone please help me out with a circuit diagram with any recommended resistors or capacitors to protect it and make it work?

Thanks in advance.

-Hans

  • 0
    TI__Mastermind 44640 points

    Hi Hans,


    I think a simpler way do perform power path control might be with either our TPS3700 (18V Tolerant) or TPS3701 (36V tolerant) over voltage/undervoltage monitor. The below concept schematic shows how this can work as absolute power path control. However, depending on your application, you may be able to reduce one of two FET's:

    The resistor divider can be selected so if over 13.5V, Choose the primary path. If under, choose the secondary. Let me know if you think this can work for your system.

  • 0
    Prodigy 20 points

    John,

    Thank you for the recommendation.  I like that the chip you recommended can be set to a wide range of threshold voltages, that should be useful.

    I don't understand how the implementation of this chip is any simpler, though...  I think I need to find another avenue, I'm just too far below the level of the help from this forum.  

    Thanks, this gave a useful part number, and I will keep on looking for help or possibly I will be able to figure it out myself.

    -Hans