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TPS61256 / Vin is Vbat with protection pack

daniel
Genius 5095 points

Hi,

My customer faced an issue:

Application is Vbat boost 5V

Battery protection pack would lock the output when VBAT<2.8V.

But it would be unlocked, and repeat on/off.

Do you have experience of VBAT with protection pack?

Thanks

Waveform and schematic:

  • 0
    TI__Mastermind 46905 points
    I think there should be a MCU to sense the battery voltage, and disable the boost converter if the open circuit battery voltage is lower than 3V (TDB, I saw some customers turn off the system when battery voltage is lower than 3.3V at no load condition).

    what the application field of this project?
  • 0 in reply to Jasper Li
    Prodigy 40 points
    I'm customer, this design without MCU for sensing battery voltage and EN pin always pull up battery power . I would like to know what factor impact battery UVLO protection become abnormal, such as choke, capacitance, DC resistance of VBAT_CONN net.
  • 0 in reply to Jasper Li
    Prodigy 40 points
    this design without MCU for sensing battery voltage and EN pin always pull up battery power. i would like to know what factor impact battery UVLO protection become abnormal, such as choke, capacitance, DC resistance of VBAT_CONN net.
  • 0
    Prodigy 40 points
    this design without MCU for sensing battery voltage and EN pin always pull up battery. i would like to know what factor impact battery UVLO protection become abnormal, such as choke, capacitance, DC resistance of VBAT_CONN net.
  • 0 in reply to CHINKUN LAI
    TI__Mastermind 46905 points
    i think the process why this happen is :
    1. the boost converter start to work because it is enable.
    2. then the load at the VOUT of the boost converter start to work.
    3. the battery voltage decrease to 2.7V because the battery has limiting energy.
    4. battery UVLO trigger and the input voltage for the boost converter drop to lower than 2V.
    5. the UVLO of the boost converter trigger and all the load shutdown
    6. the battery voltage recover because there is no load at its output.
    7. repeat the first step again.
  • 0 in reply to Jasper Li
    Prodigy 40 points
    i don't understand why VBAT stooped at 1.5v around 2ms, then rise to 2.9v suddenly. It should be fall down 0v not 1.5v under protect definition.
    Do you know how to resolve this issue?
  • 0 in reply to CHINKUN LAI
    TI__Mastermind 46905 points
    i think the capacitor hold the voltage at 1.5V because there is no load at VBAT=1.5V condition. after 2ms, the battery reset its UVLO circuit.
    as i mentioned, the boost converter should be disabled at VBAT< 3V. from current information, it is a problem related to the power system. not the boost converter. so i don't think modify the external component of the boost converter would help this problem.