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battery remove emulation

Bartlomiej Swierczek
Prodigy 100 points
Other Parts Discussed in Thread: TPS65930, OMAP3530

Hi all,

 

I am working on a design using OMAP3530 and TPS65930.

System has to be powered from 2-Cell Li-Ion battery (max 8.4V) or 12V DC wall supply and TPS65930 provides the main power rails to the board and has a maximum limit of
4.7V on its VBAT input and a nominal of 4.2V (minimal 3.3V).

To meet TPS65930 requirement there need to be used DC-DC regulator to convert those input voltages in range about 5-12V to 4.2V. I will use Switching DC-DC Buck Converter.

 

Final device need to operate in following modes:

1 On/ Full Active,

2 Hibernate/Deep sleep mode,

3 Power Off mode,

 

Power Off mode I understand as VBAT=0V for TPS65930 and 4.2V Dc/Dc Converter is OFF. That will be something like battery removal emulation.

 

My question is:

Q: Is there any possibility to turn off DC-DC Buck Converter using OMAP / TPS65930 Signals (sys_off_mode/nSLEEP, SYSEN, REGEN, GPIO...) or additional logic under Omap control?

 

Thanks,

Bartek Swierczek

  • 0
    TI__Genius 15100 points

    Hi,

    Comments and answers:

    The power off mode you talk above looks like the power off mode of the system (you have) and not of TPS65930. Just wanted to clarify this. In case you are talking about power off mode for TPS65930 then, this device can stay powered off with VBAT active. This is called as the waiton state in the document.

    Are you asking a way to turn of the external DCDC buck used for converting 5-12V to 4.2V?

    This can be controlled by GPIOs from OMAP or TPS65930. However, this control will take down the power the the system and there needs to be some means to power the system back ON. Switching OFF the buck will power OFF TPS65930 and hence also OMAP.

    Do you intend to this?

     

    Regards,

    Gandhar.

     

  • 0 in reply to Gandhar Dighe
    Prodigy 100 points

    Gandhar Dighe said:

    Hi,

    Comments and answers:

    The power off mode you talk above looks like the power off mode of the system (you have) and not of TPS65930. Just wanted to clarify this.

    [...]

    Are you asking a way to turn of the external DCDC buck used for converting 5-12V to 4.2V?

    Yes, I am talking about the power off mode for the whole system and i would like to do this by turning off DCDC buck converter (which is placed "between" battery and TPS65930)

     

    This can be controlled by GPIOs from OMAP or TPS65930. However, this control will take down the power the the system and there needs to be some means to power the system back ON. Switching OFF the buck will power OFF TPS65930 and hence also OMAP.

    Do you intend to this?

     

    I know the way to switch on buck converter. I will use additional LTC2954 Push Button On/Off Controller. That device has nKILL input , the low status of this entry causes an immediate shutdown of the buck regulator. That device will switch ON buck converter after power push button pressed => VBAT raises and that suppose to SWITCH ON TPS65930 to ACTIVE state and run OMAP.

    Am I correct?.

     

     

    SYSTEM POWER OFF scenario, I would like to implement is  as follows:

    1. trigger from pushbutton or software 
    2. OMAP operating system (Linux) closes, last step - drive GPIO to system power off
    3. SYSTEM POWER OFF, switching OFF the buck, power OFF TPS65930 (NO SUPPLY state)

    Is it allowed to (it will no harm TPS65930 and/or OMAP) switch system power off after linux closes without driving TPS65930 or OMAP to WAIT-ON state?

     

    Regards,

    Bartek Swierczek

  • 0 in reply to Bartlomiej Swierczek
    TI__Genius 15100 points

    Hi,

    I would consider this as an abrupt power disconnection and not a standard way to power down the device. When power is lost to the device it will lose all stored data ( I am assuming you do not have a backup battery, please confirm this).

    At next power up it will power up as a fresh power up cycle and resume default state.

    For OMAP - you may want to ask the OMAP support teams. I am not able to comment how this type of power off will affect OMAP.

     

    Regards,

    Gandhar.