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TPS65217 BeagleBone Black 5V AC Input

Travis Jett
Prodigy 20 points
Other Parts Discussed in Thread: TPS65217

We've developed a custom cape for use with the BeagleBone Black Rev C. The cape supplies 5V to the BBB at Pin 3 of J9 which goes to the AC input of the BBB. The cape is connected to a 12V supply and features a supercapacitor backup supply when 12V is removed. Once the supercapacitor voltage drops to around 4.3V, the BBB shuts off. If 12V power is reapplied, the power does not come back on unless the capacitor voltage (AC) drops to below 3.3V. Is this normal functionality of the TPS65217?

Thanks,

Travis

  • 0
    TI__Genius 10885 points

    Hi Travis,


    The behavior of the TPS65217 heavily depends on the voltage of the BAT pin as well, so what is the voltage on that pin during this condition?

    Ultimately, most behaviors of the TPS65217 can be explained by simultaneously monitoring the input power (AC/USB/BAT) and the PWR_EN pin, as this controls when the DC/DCs are enabled. PWR_EN behaves differently depending on the states mentioned in Figure 20 of the datasheet, and so does VLDO1 which I believe is the original source for PMIC_POWER_EN on the BBB.

    So this behavior might be normal depending on the conditions of these inputs.

  • 0 in reply to Richard Solarski
    Prodigy 20 points
    Thanks Richard. I will monitor those signals with an oscilloscope or DMM and report back the voltages during these conditions.

    Thanks,

    Travis
  • 0 in reply to Travis Jett
    Prodigy 20 points

    Did this issue get resolved? I have the same issue where removing the AC input causes a clean shut-down on the Beaglebone (3.8.13-bone79, Debian 11): " Power button pressed The system is going down for system halt NOW!.  However I need the device to switch to BAT power and continue to run. Oddly, when powered from USB (instead of AC) there is a smooth transition to BAT power).

    Is there a register on the TPS65217 that can be set to change this behavior?

    Thank you,

    Bolek

  • 0 in reply to Boleslaw Mellerowicz
    TI__Genius 10885 points

    Hi Bolek,

    Per the system message, is the Power Button actually being pressed?

    The PMIC should transition to a battery whether AC or USB was the initial source without any additional configuration necessary, and since you are getting a system shutdown message I'd suspect there is some software routine that monitors the TPS65217 STATUS registers and issues a shutdown command when AC is removed.

  • 0 in reply to Richard Solarski
    Prodigy 20 points
    Hi Richard,

    Thank you for the quick reply. The button was not being pressed. Removing the AC power with the battery connected triggers the shut-down.

    Perhaps the BBB kernel is looking at the the ACPWR bit of the STATUS register. Are there any other registers/bits you think it might be monitoring that could trigger this behavior?

    I will have a look at the kernel code of my BBB (3.8.13-bone79 running Debian 11) and learn how to modify it. I found this thread as a start:
    www.mail-archive.com/.../msg37411.html

    If you know any other links that could help please send them my way.

    Thanks,

    Bolek