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BQ25180: Hardware reset and VSYS configuration

Francisco Zamudio
Prodigy 80 points
Part Number: BQ25180
Other Parts Discussed in Thread: BQ27427

Tool/software:

Hello team,

I've been working with the BQ25180YBGR, but I can't set the reset button to make VSYS low. I've tried to condigure the VSYS according to the datasheet, using the SYS bits, and also using the reset input, but it doesn't work, so, I would like a double check on the schematic. I've removed Q3 just incase that it is making some problems, but the behavior is the same. This is the schematic that I have for the battery managment. 

This is the final configuration that I've used

reg 3 = 0x46,

reg 4 = 0x2F,

reg 5 = 0x30,

reg 6 = 0x56,

reg 7 = 0xC4,

reg 8 = 0b00011011,

reg 9 = 0b01101101,

reg 10 = 0b00101100,

reg 11 = 0x00,

reg 12 = 0xc0

This is the test result. I can see a try on VSYS, but it doesn't go low.

 

 

Please, let me know if you have an idea. I've seen the test result on the datasheet and seems that It whould work. 

Regards

Francisco

  • 0
    TI__Expert 8070 points

    Hi Francisco,

    Thanks for reaching out and for sharing all of this information.

    I've reviewed the BQ25180 portion of your schematic. The only issue I see is that there is a 100nF capacitor on the VIN pin while it's recommended to use at least a 1uF capacitor. Otherwise, the schematic looks good. I don't see any issues with the TS/MR pin configuration or the low-side switch circuit.

    It seems that there could be an external supply or rail that's holding SYS up during the hardware reset attempt. I don't see any issues with your register configuration other than SYS_MODE = 11 (SYS pulldown enabled). However, in the waveforms you shared, it doesn't appear that SYS (blue?) is pulled down. Could you confirm whether SYS_MODE = 11 during the waveforms you shared? If so, that would indicate that something in your design is pulling SYS up. Also, I saw that EN_RST_SHIP = 11, which will immediately perform a hardware reset when written, so just note that these bits don't need to be written to perform a hardware reset using the pushbutton.

    Let me know if there's anything pulling SYS up in your design.

    Best regards,

    Alec

  • 0 in reply to Alec Lehman
    Prodigy 80 points

    Hi Alec, 

    Thank you so much for your feedback. Have you seen the interconnection with the Fuel Gauge? is it ok? Can you please review that one?

    Regards

    Francisco

  • +1 in reply to Francisco Zamudio
    TI__Expert 8070 points

    Hi Francisco,

    Thanks for pointing that out. I can loop in the battery fuel gauge experts for further review of the gauge schematic, but the SRX pin of the BQ27427 is connected to the BAT pin of the gauge through an internal sense resistor. This means that the sense resistor in the gauge is effectively in parallel with the BATFET (Q3) of the charger in your design, so even when the BATFET is turned off during a hardware reset, the battery is still connected to VSYS through this sense resistor.

    I'd recommend connecting the SRX pin of the gauge, rather than the positive terminal of the battery (BATT), to the BAT pin of the charger. This way, the gauge can sense the battery current, and the BATFET of the charger can be used to disconnect the battery from SYS.

    Best regards,

    Alec

  • 0 in reply to Alec Lehman
    Prodigy 10 points

    EDIT: As I was typing this message, I noticed you left another comment about 15 minutes ago. Feel free to disregard this message if it's no longer relevant.

    Alec, thanks for your response. I'm a firmware engineer that works with Francisco, an electrical engineer. Earlier today, as I was reviewing the register configurations, I noticed the same issue you mentioned with the hardware reset being initiated. This was a simple misunderstanding that Francisco made when trying to configure the push button long-press action to perform a hardware reset (as set in the adjacent bits). This has since been fixed.

    You mentioned the following

    "I don't see any issues with your register configuration other than SYS_MODE = 11 (SYS pulldown enabled). However, in the waveforms you shared, it doesn't appear that SYS (blue?) is pulled down."

    To clear up any confusion, setting SYS_MODE to b'11 was intentional, and SYS not being pulled down is the issue we're trying to figure out.

  • 0 in reply to Matthew Llarena
    TI__Expert 8070 points

    Hi Matthew,

    Thanks for reaching out and checking the firmware. This issue does appear to be in the schematic, but please feel free to let me know if there are any other register configuration questions.

    Best regards,

    Alec

  • 0 in reply to Alec Lehman
    Prodigy 80 points

    Hi Alec, 

    Thank you so much for your feedback about this case. I tried to get a riview while ago for this design, and it supposed it was ok, this is the post  BQ21080: NCT range and reference design 

    So, does that mean that the Fuel Gauge should be connected to the Input Voltage from the charger? Something like this? 

    Regards

    Francisco

  • +1 in reply to Francisco Zamudio
    TI__Expert 8070 points

    Hi Francisco,

    1. Disconnect the SYS pin of the charger from the SRX pin of the fuel gauge.

    2. Disconnect the battery positive terminal (BATT) from the BAT pin of the charger.

    3. Connect the SRX pin of the fuel gauge to the BAT pin of the charger.

    In this configuration, the charge current will flow from the input of the charger, through the charger to the BAT pin, then from the BAT pin to SRX of the gauge, through the internal sense resistor of the gauge to the BAT pin of the gauge, and finally through charge and discharge FETs of the battery protector to the battery.

    Best regards,

    Alec