• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 64 subscribers
  • Views 938 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ24092 will not charge a discharged battery

Luis Olvera41
Prodigy 160 points
Other Parts Discussed in Thread: BQ24092

Dear TI support staff,


We are implementing a BQ24092 linear charger IC in one of our products to charge a 4.2V 1600mAh Li-Polymer battery with built-in PCM (no thermistor) however it is unable to charge a discharged battery. By discharged battery I refer to a battery whose under-discharge voltage protection (2.8V) has been trigerred and thus protected by the PCM (as normally happens).

It does charge and work fine if the battery has more than 3V.

Power is supplied by an inductive charging station. Receiver power is 5W output voltage 5V.

The battery is connected to a system load (approx. 1.2W) consisting of:

- Boost constant current driver for a LED string.

- Boost constant current driver for a heater (for the battery since the charger will operate in -10°C to 10°C.

- Microcontroller (basically to dim LEDs control the heater and monitor battery voltage)

The charger is configured with a 5K90 resistor connected from PRE_TERM to ground to supply 600mA to precondition the battery (effectively 200mA as the system "steals around 400mA @ 2.9V) and to supply 1A at its constant current phase (effectively around 700mA) with a 549R resistor from ISET to ground. However Vout remains about a few millivolts.


So far we have tried setting TS to high, float, and also connecting a 10K resistor to ground. Is there something we are missing?

Thanks in advance,

Luis Olvera.

  • 0
    TI__Prodigy 725 points
    Hello Luis,
    Can you please send / post a diagram of your complete circuit? Note that the bq24092 does not have any power path function. Thus if you have a battery that has disconnected due to overdischarge, and you also have a system load attached to the charger's output pin, there will not be a good way for the system to power up.
  • 0 in reply to Upal Sengupta
    Prodigy 160 points
    Greetings Upal,

    I understand that the IC doesn't have a power path but isn't it able to supply 4.2V even without a battery connected?

    I don't fully understand what the TTDM function is for could you please elaborate.

    Today we tested a board without the battery connected (and TS tied to Vout): if we wait for the BQ24092 to start without the load (it does put 4.2V on its output) and then load it with the LED string and the heater it is capable of sourcing enough current to maintain the whole system. But it doesn't source power if we attempt to start the system with the loads connected (with or without a discharged battery)

    I can send you the schematic please provide me your corporate TI e-mail address.


    Thanks in advance,

    Luis Olvera.
  • 0 in reply to Upal Sengupta
    Prodigy 160 points
    Upal,

    Sadly we haven't heard from you... is everything alright?


    Luis Olvera.
  • 0 in reply to Luis Olvera41
    TI__Expert 7730 points
    Luis,

    The device has a battery detection routine in which the output signal will be dump between 3.9V to 4.2V when there is no battery connected. In TTDM mode, this routine is disabled so you will see a stable output signal at 4.2V. What is the total load from the LED string? When the system is not able to provide the power, what is the voltage at OUT pin and VIN pin?

    Please send the schematic to wenjia.liu@ti.com.

    Thanks,
    Wenjia