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Regarding bq24075 Li-ion charger with System Load

Gary Yim
Prodigy 20 points
Other Parts Discussed in Thread: BQ24075, TPS61032

I am considering this part bq24075 for my load 5V  with 1.2A peak. The Vin is 5V with 1.5A peak.

I want to have the battery charging and 5V output at the same time, when there is a 5V Vin. But I need to have a switch to control the Vout ON/OFF, when there is no input.

 I have a question here as:

1.  If there is no input, the Li-ion battery can only output ~3.7V? Do I need to add a boost circuit to boost 3.7V to 5V for my load?

2.  For the question 1, if there is much better parts for this application?

3. Can I use the pin SYSOFF of the bq24075 for the switch control the ON/OFF

4. If  bq24075 support battery over dis-charge protection? If no, any parts support this function?

Gary

  • 0
    TI__Mastermind 32400 points

    Hi Gary,

      

    1.  If there is no input, the Li-ion battery can only output ~3.7V? Do I need to add a boost circuit to boost 3.7V to 5V for my load?

    Yes, you will to boos it up to 5V

    2.  For the question 1, if there is much better parts for this application?

     

    3. Can I use the pin SYSOFF of the bq24075 for the switch control the ON/OFF

     

    Yes, The bq24075 features a SYSOFF input that allows the user to turn the FET Q2 off and disconnect the battery from the OUT pin.

     

    4. If  bq24075 support battery over dis-charge protection? If no, any parts support this function?

    When no source is connected to the IN input, OUT is powered strictly from the battery. During this mode the current into OUT is not regulated, similar to Battery Supplement Mode, however the short circuit circuitry is active. If the OUT voltage falls below the BAT voltage by 250mV for longer than tDGL(SC2), OUT is turned off. The short circuit recovery timer then starts counting. After tREC(SC2), OUT turns on and attempts to  estart. If the short circuit remains, OUT is turned off and the counter restarts. This ON/OFF cycle continues until the overload condition is removed.

     

    Thanks

    Tahar

  • 0 in reply to Tahar Allag
    Prodigy 20 points

    Hi, Tahar

    Thanks for your reply.

    I'm going to use tps61032 for the boost circuit. There is a Low Battery Detector Circuit—LBI/LBO.

    It mentioned:

    "The low-battery detector circuit is typically used to supervise the battery voltage and to generate an error flag

    when the battery voltage drops below a user-set threshold voltage. The function is active only when the device is
    enabled. When the device is disabled, the LBO pin is high-impedance. The switching threshold is 500 mV at LBI.
    During normal operation, LBO stays at high impedance when the voltage, applied at LBI, is above the threshold.
    It is active low when the voltage at LBI goes below 500 mV.

    "

    I have a question :

    1. When the voltage at LBI goes below 500 mV and LBO active low, the circuit will auto turn off? Or I need to set the EN pin once the LBO active low?

    Thanks,

    Gary

  • 0 in reply to Gary Yim
    TI__Guru**** 167196 points

    The TPS61032 does not auto turn off when the voltage at LBI drops below 500mV.  Also, if the TPS61032 EN pin is low, LBI/LBO function is disabled.