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BQ24770: Device not working under default setting

Roy Hsu
Genius 9390 points
Part Number: BQ24770
Other Parts Discussed in Thread: EV2400, BQ24773,

Hi there,

We observed a strange phenomenon today and it seems that the device configuration needs to be written to the device even the configuration is the same as the default state at startup.

Please refer to the two waveforms below. (CH1: Vsys, CH2: Load current, no battery is connected)

This waveform was taken after the device was powered up. As you can see, large voltage ripple exists under 4A of load current.

Now, we wrote the configuration (same as the default state) manually via EV2400 to the device after the device was powered up, then we started to draw current.

As you can see, the voltage ripple no longer exists. We also observed the same phenomenon on the BQ24773 EVM.

Therefore, we think BQ24770 needs manual configuration update at startup so that it can work properly.

I can send you the schematic if you think that's needed.

Please help clarify! Thanks!

Best regards,

Roy Hsu

  • 0
    TI__Guru 56650 points
    bq24770 and bq24773 both have auto-wakeup function which provides 128mA small current to BAT output to wake up a deeply discharged battery. If the battery is not connected, this small current can push the output voltage high until triggering an internal protection. When the output voltage goes back, it will provide this current again.

    When you send a command to the charger, charger knows the system or host know the right charge current setting. So, it would run into a normal charger voltage and current regulation. As you can see, the voltage ripple no longer exists.

    This is a normal behalf. That is why in the datasheet page 32, we put "When battery is absent, the host should write 0A to ChargeCurrent()."