Battery Supplies for IC

Discussion in 'Power Electronics' started by Ramon Jimenez, Sep 6, 2016.

  1. Ramon Jimenez

    Thread Starter New Member

    Jun 30, 2016
    Hello! I am hoping someone could help me with my circuit that I am working on. This is my first real design so I apologize if anything is remedial and I hope you can teach me in the process.

    Attached is the schematic that I am working on. Basically it is a BT wearable that I am designing. The MAX1551 Battery charge IC is connected to the battery to monitor its charge, and that battery is directly connected to the supply load (Pins for IC, LED, & through holes that will be for a vibrating motor disc)
    Screen Shot 2016-09-06 at 10.09.28 PM.png
    My question is does this setup look right? I will be adding a switch to the supply load to conserve battery power, but is this all I would really need to do? I feel like this is too good to be true.

    Another question: how do I figure out the charge rate / discharge rate of the battery from the loads? I read the data sheets but not really putting two and two together.
  2. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
    The CHG/POK pin (depending whether you are using MAX1555 or MAX1551) is an open drain output and is pulled low when charging so the LED cathode should be connected to this pin and its anode connected via a resistor (470 Ω perhaps) to the battery.
    It would probably be a good ide to connect the DC pin to ground rahter than leave it floating.
    The datasheet for these devices requires a 1uF ceramic capacitor to be connected to ground within 1cm of the USB and BAT pins.
    The charge current will be 100mA maximum. The discharge rate depends on how much current your load draws from the battery.
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Your 'vibrating motor disc', if inductive, will require a catching diode across it.