• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 63 subscribers
  • Views 1858 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS65217: The purpose of BAT/BAT_SENCE capacitance

Hayashi
Expert 1840 points
Part Number: TPS65217

Hi teams,

The TPS65217 will reset after 1 second, if BAT and BAT_SENCE are connected as shown in the data sheet as shown in the data sheet, after the PMIC power-down operation.
However, this restart condition has been eliminated by connecting a 10 μF capacitor between GND as shown in Application Note (Designing TPS 65217 Systems for VIN Brown - Out Without a Physical Push - Button) Case A described.
Is there any reason why this can be solved by connecting a 10uF capacitor to this BAT, BAT_SENSE pin?
Best regards.
Hayashi
  • 0
    TI__Mastermind 30310 points

    The App Note you mentioned does not say to connect a 10-uF capacitor from BAT and BAT_SENSE to GND to solve the issue.

    As you can see in the below picture, the problem is resolved with a 10-kOhm resistor labeled RLL (light load).

    The purpose of the BAT pin is to connect a single-cell Li-Ion or Li-polymer battery. The TPS65217 PMIC can charge the battery using power from AC (an AC-DC adapter producing 5V DC at high current) or USB (5V limited to 500mA) and use the battery as a power supply to the system. The BAT_SENSE pin is to detect the presence of a battery and the voltage on the battery to determine which part of the charging cycle to enter. Leaving the BAT_SENSE pin floating without it being shorted to the BAT pin does not help the PMIC determine there is no battery. The BAT and BAT_SENSE pins must be shorted together. If they are shorted together and left "floating" with a 10-uF capacitor, then this capacitor will get charged by the voltage on the SYS pin when the AC or USB power is removed. This charge on the capacitor acts similarly to a weak battery, so the device digital + analog detection is still running and able to detect AC removal. If AC browns-out and returns to a normal voltage while this capacitor is still charged, then AC removal never occurred and there will not be a wake-up event to return to the ACTIVE state. The 10-kOhm resistor to GND instead of a 10-uF capacitor prevents this build-up in charge and the problem does not occur.

    The problem generally arises from not using a battery in the system. The PMIC is designed to work with a battery, but the Beagle Bone Black reference design does not include a physical battery when it is shipped because shipping Li-Ion batteries is difficult for legal reasons. Most people assume the battery is not required. The PMIC can work without a battery, but it requires some additional consideration. This is the purpose of the App Note.

  • 0 in reply to Brian Berner
    Expert 1840 points
    Brian-san

    Thank you for your reply.
    But, my customer don't solve this problem.

    Please let me know how to use the OVP from AC supply.

    They want to use the function of OVP from AC.
    You teach me the above idea, it cannot use OVP because AC connected to GND.

    I told them, I think the application report (SLVA901) #3.2 can work the OVP in AC.
    But, when the AC supply, It did not improve symptoms restart began to put it again.

    Best regards
    Hayashi
  • 0 in reply to Hayashi
    TI__Mastermind 30310 points

    Hayashi-san,

    Yes, it is quite simple to use AC as the only power into the TPS65217 PMIC to get OVP protection benefits.

    Solution Circuit Number 2 for Case A (No Battery) is shown in Figure 7 on page 9 of SLVA901, and this will work for the majority of applications. All the customer needs to do is short BAT and BAT_SENSE together and then pull-down to GND with a light loading resistor (1-10kOhms) which will ensure there is no charge build up on BAT pins when AC is removed.

    If customer's system requires VIO of the PMIC to be provided by a separate discrete DC-DC converter or LDO, then the resistor will not work because VIO > VAC and there is a leakage path through the TPS65217 that will pull up the BAT and SYS pins. This is Case B on page 6 and can be resolved in a different way:

    Solution Circuit Number 3 for Case B, shown in Figure 10 on page 10.

  • 0 in reply to Brian Berner
    Expert 1840 points
    Brian san
     
    Thank you for your supports.
    My customer have still not to be solved about the action of this device will restart.
     
    The state diagram in datasheet, I think, if the device remains in the EN= 0 state, the device will not start up.
    However, the device will restart after 1sec unexpectedly.
     
    As a result of consideration of countermeasures by customers, reducing the capacity of the entire capacitor or
    by adding a capacitor in parallel to the RLL of the Application Report 3.2, the restart operation no longer occurs.
     
    Would you mind to tell me your thoughts from this result.
     
    Best regards.
    Hayashi
  • 0 in reply to Hayashi
    TI__Mastermind 30310 points
    Hayashi-san,

    Starting up after 1s is not unexpected.



    Starting up for the 1st time (all input power = 0V and all capacitors with no charge on them) should always be immediate with a short de-glitch time of 55ms. This would be a "cold boot", starting from the "POWER DOWN" state of the PMIC.

    Any other start-up after the first time can be referred to as a "warm boot", and is a transition from 1 state to another. Every "warm boot" will go through a 1s timer, WAIT MIN OFF TIMEx (1 s), shown in the Global State Diagram, Figure 24 of the TPS65217 datasheet.



    All 1s delays can be explained using these timers.



    Unless you provide detailed schematics showing the wiring of the customers system and scope shots documenting the issue the customer is observing, this is the best information I can provide. To me, it sounds like the PMIC is behaving correctly and it has not locked up. As long as SYS=VIN (AC, USB, or BAT) after all timers have expired, then the device is entering the ACTIVE state correctly.
  • 0 in reply to Brian Berner
    Expert 1840 points
    Brian-san,

    Thank you for your reply.
    I would like to send you schematics if you can check.
    My e-mail address is "ta-hayashi@fujiele.co.jp".

    Best regards
    Hayashi
  • 0 in reply to Hayashi
    TI__Mastermind 30310 points
    Hayashi,

    Can you attach portions of the schematic on e2e without sharing NDA information?

    If you cannot share any portion of the schematic in Public e2e forum, then you will need to contact your local TI Sales Representative to start email discussion. The TI Sales team can easily get in contact with our team and help ensure communication is reliable to fix the issue.