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Original question:

BQ24195: Problem switch to powering

BQ24195: Set boost mode using i2c-tools

Manuele Conti
Prodigy 30 points
Part Number: BQ24195

Tool/software:

When I turn on my board with both the power supply and a battery connected (4.17V), this is the output I receive:
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x0
0x30
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x1
0x1b
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x2
0x60
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x3
0x11
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x4
0xb2
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x5
0x9a
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x6
0x03
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x7
0x4b
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x8
0x34
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x9
0x80
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0xa
0x23

Disabling Watchdog:
root@verdin-am62-15133450:~# i2cset -y 1 0x6b 0x5 0x82

Checking Faults:
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x9
0x80
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x9
0x00

Attempting to set Boost Mode
- REG[5:4] = 10: (REG01 & 0xCF) | 0x20
root@verdin-am62-15133450:~# i2cset -y 1 0x6b 0x1 0x2b
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x1
0x1b

- REG[5:4] = 10: (REG01 & 0xCF) | 0x30
root@verdin-am62-15133450:~# i2cset -y 1 0x6b 0x1 0x3b
root@verdin-am62-15133450:~# i2cget -y 1 0x6b 0x1
0x1b

It seems like I am unable to switch the device into Boost mode to get 5V from PMID pin when power supply is turned off.

What could I be doing wrong?

  • 0
    TI__Genius 17905 points

    Hi Manuele,

    Can you please share your device schematics?

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 30 points

    Hi Juan,

    of course

  • 0 in reply to Manuele Conti
    TI__Genius 17905 points

    Hi,

    Thank you for sharing the schematic. I'll take a look to see if I identify any issues with it. There is a few more questions I have:

    - What is your battery voltage at this time?

    - If possible, can you please share a waveform of +V5_BQ and +V5_Supply before you enable OTG and once you try to enable it? Based on the REG08 there appears to still be voltage present on VS (Power Good is set).

    - Even after a 220mS wait, if you readback the register value it is still 0x1B?

    Also, please note we typically recommend this kind of isolation circuit at VBUS  if OTG is being used. This is to prevent power from reaching the power source and to ensure that the device OTG works as intended:

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 30 points

    What is your battery voltage at this time?

    4,19V

    - If possible, can you please share a waveform of +V5_BQ and +V5_Supply before you enable OTG and once you try to enable it? Based on the REG08 there appears to still be voltage present on VS (Power Good is set).

    +V5_BQ before

    +V5_BQ after

    +V5_SUPPLY 

    - Even after a 220mS wait, if you readback the register value it is still 0x1B?

    Yes

  • 0 in reply to Manuele Conti
    TI__Genius 17905 points

    Hi Manuele,

    It looks like there is still 5V present on VBUS before you try to enable the boost mode on this device. One of the requirements for entering boost mode is that VBUS must be less than VBAT+Vsleep.

    Is your VIN still present when you attempt to enter boost mode?

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 30 points

    It is true, but if I remove the power supply, the voltage drops to 3.8 and the board shuts down, so I can't set the register. This is why I thought it was possible to set the register before, but now I'm not sure how to proceed.

  • 0 in reply to Manuele Conti
    TI__Genius 17905 points

    Hi Manuele,

    Typically, the battery-powered device is powered off the SYS rail and can either sustain itself for across the battery voltage range (3.3V - 4.2V) or has a buck-boost in order to keep a constant 5V.

    Boost mode is typically used to power connected devices (battery-powered device serving as a powerbank) or to power peripheral components, not necessarily the host MCU.

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 30 points

    Hi Juan,

    Thank you for the information. To ensure the board remains powered when VBUS drops, I plan to use the BQ24195. I will enable boost mode after the OS is booted to maintain power from the battery. During shutdown, boost mode will be turned off.

    So, I am considering lowering the VBUS by 80mV (VSLEEP) as part of this setup. Could you please confirm if this approach is correct?

    Please let me know if you have any additional insights or suggestions.

    Best regards,
    Manuele

  • 0 in reply to Manuele Conti
    TI__Genius 17905 points

    Hi Manuele,

    To confirm lowering VBUS below VSLEEP would require lowering VBUS below VBAT + 80 mV. So if a battery is very discharged, say VBAT = 3.4V, then you would have to lower VBUS to 3.48V. Would that work for your application?

    Best Regards,

    Juan Ospina