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BQ24193 System Over-Current Protection

Teik Hooi Teoh
Intellectual 655 points

Hi,

In datasheet page 11 under Charger Over-Current Comparator:

I(BATFET_OCP) = 9A (min.).

Is this referring to the OCP limit of current path from BAT pin input to SYS output as described in Battery Protection - System Over-Current Protection (page 33)?

If yes, what should be the expected behavior and maximum voltage drop in V(BAT) and V(SYS)?

Any recommended test setup condition for this measurement?

  • 0
    TI__Expert 8690 points
    Hi Teik,

    I(BATFET_OCP) = 9A (min) refers to the current discharging from the battery (BAT) to the system (SYS). This should only be due to a relatively small transient, and not because the system demands more than 9A as average load.

    This protection is in place if system somehow gets shorted, then BATFET turns off.

    Before BATFET_OCP, VSYS=VBAT-IBAT*BATFETrdson, and VBAT is the voltage of the real battery terminal minus the voltage drop across the line (VBAT=VBATterm-IBAT*Rline).

    During BATFET_OCP, BATFET turns off, no current going in/out of BAT, VBAT stays in its current value, VSYS will drop because not enough current is being supplied.

    To test, limit input current from VBUS (if input is connected), and force a high load on SYS pin. Make sure to use necessary precautions and a battery/powersupply which can handle the load. It is not typical to have very high currents passing through BATFET, but this protection is there to provide safe operation in the case this actually happens.

    Thanks,
    Steven
  • 0 in reply to Steven Bangdiwala
    Intellectual 655 points
    Hi Steven,
    Thanks for the helpful reply.
    So I suppose this OCP will only kick in under transient condition (eg. short at system load side).
    But what will happen if the system load is increased in a continuous steady manner, would the OCP be activated?

    Regards,
    Teoh
  • 0 in reply to Teik Hooi Teoh
    TI__Expert 8690 points

    Teoh,

    This BATFET_OCP will also trigger if a high continuous current is passing through BATFET. Both a high transient or continuous current will activate BATFET OCP.

    Regards,
    Steven