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BQ24105: selection of zener diode, deactivation of TS(Temperature sense)

Jaeseung Jeong1
Prodigy 130 points
Part Number: BQ24105

The diode D1(MMBZ18VALT1) was used on the bq24105 datasheet, but no diode was used on the bq24105 evaluation board.


1. Do I need to use a gener diode? I wonder why use it. If the output is 8.4V should I use a gener diode with a 9V breakdown voltage?

2. I have a 2-Cell battery pack with only 2 power line (temperature line removed). So to disable the temperature monitoring function by applying a constant voltage to the TS pin. How do you calculate the voltage?

   VLTF = Vo(VTSB) x %LTF+100 / 100
      Vo(VTSB) = 3.15V
      %LTF+100 = ?? (Not found in datasheet)


  • 0
    TI__Guru**** 165886 points

    Hi Jaeseung,

    Regarding 1, the Zener is actually an 18V TVS, fast transient suppressor.  It is meant to clamp switching spikes at the OUT pin.  I recommend adding that device or similar as close to the IC as possible. 

    Regarding 2, by sizing the resistor divider to keep the TS between VLTF=73.5%xVTSB and VHTF=34.4%*VTSB thresholds, TS is effectively disabled.  You could use matching 10k-100kohm resistors to set TS at 50%xVTSB.

    Regards,

    Jeff