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BQ24190: SYS Regulation to 3.5V not working

Disco Inferno
Prodigy 90 points
Part Number: BQ24190
Other Parts Discussed in Thread: BQ25890

Hello,

Please Help!

 

I have a BQ24190 Evaluation board and am having trouble with the Narrow DC SYS output (Minimum System Voltage Regulation).

According to the data sheet, it should automatically regulate the SYS up to 3.5v (default) when the battery is below that value.

My output design has a 3v3 linear regulator that needs headroom so this feature is critical for me.

I cannot get the device to regulate the SYS to 3.5v (Minimum system voltage) no matter what registers I set or configuration I try.

Per the data sheet; I have a DC supply set to 3.2v and 2A on the BAT+ and GND terminals, I have also tried lower voltages down to 2.2v.

The SYS output ALWAYS follows the battery voltage, except when it is charging the battery, then it jumps up to 4.2v.

I can only get the device to go into "System Regulation" when the VBUS is connected to a USB device (charger) and the "OTG" is disabled.

Can you please advise a specific configuration to get the device to perform this on the Evaluation Board (bq24x9xEVM )?

I chose this chip because it seemed to be able to do this as a default, even independently without any Host commands.

Thank you in advance for your reply.

  • 0
    TI__Genius 10240 points
    The minimum system voltage is regulated when the the battery voltage is below the minimum system voltage AND the adaptor (Vbus) is present. The minimum system voltage is the output of the buck convert from the Vbus as the input. Did you provide Vbus and how much is the Vbus voltage? Did you check the SW waveform and make sure the converter is operating?
  • 0 in reply to ezhao
    Prodigy 90 points

    Thank you Ezhao for the answer. Your statement about the chip needing VBUS and battery lower than system minimum makes sense.

    I can get the system to go into regulation when I have an Adaptor plugged into VBUS and the battery is lower than minimum thrreshold.

    I was really hoping this chip could provide minimum system voltage WITHOUT an adaptor present.

    Are you able to confirm that the BQ25890 also requires VBUS to provide minimum SYS voltage threshold?

    -Do you know any other chip that can provide minimum voltage without an adaptor connected?

    Thank you again.

  • 0 in reply to ezhao
    Prodigy 90 points

    Thank you  Ezhao.