schematic explanation help

Discussion in 'General Electronics Chat' started by kaning, Jul 7, 2014.

  1. kaning

    Thread Starter Member

    Jun 2, 2014
    43
    0
    Hi, im building a NiMH battery charger and im thinking about using the BQ2002 for charging controller. while reading datashee of one of this component aplication datasheet i got problems understanding whats there and i need some help. i know how the pin works i just need help understanding something on the schematic, on pin TS.

    datasheet
    http://www.ti.com/lit/ug/sluu007b/sluu007b.pdf

    schematic
    http://forums.parallax.com/attachment.php?attachmentid=102068&d=1370352706

    in the datasheet, below image says, R5 is 3,57kΩ and R18 is open. what does that mean??

    i think those 100k near pin is for current limiting am i right?
    someone give me some lights here please, whats is going on that pin? thanks!

    p.s.
    voltage temperature cut off = Vtco=0.5*vcc=0.5*5=2.5v
    voltage temperature sensor=Vts

    if vts> vtc charges batteries
    else stops charging

    so r5 and thermistor are voltage divider to pin TS where thermistor resistance drops with temperature until gets 2,5v or below and cuts off. what about r18 and r17?
     
  2. kaning

    Thread Starter Member

    Jun 2, 2014
    43
    0
  3. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    When they say a resistor is "open", they mean that it is not there. It is an open circuit.

    Yes, the 100K is for current limiting. The other resistor, R5, and the thermistor form a voltage divider, so the voltage at the TS pin changes over temperature.
     
    kaning likes this.
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