• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 62 subscribers
  • Views 785 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TPS65721 Reset Button

BuffaloEngineer
Intellectual 680 points

We have a momentary switch that we intended to use as a reset button - it pulls PB_IN' to the system voltage (SYS) when pressed.  Otherwise, there's a 100k pulldown to GND.  

The switch works fine, but the device is not reset.  Am I misunderstanding the function of PB_IN'?  

If I want to power cycle the device, should I use HOLD_DCDC1 and HOLD_LDO1 instead?  

Thanks very much!

  • 0
    TI__Genius 16870 points

    PB_IN is for the power after the battery has been removed or on first power up. You can monitor PB_IN with a uC and shutdown LDO and DCDC to reset. This would be good for a requirement of say 5s hold time initiates a shutdown event...

  • 0 in reply to Michael Green
    Intellectual 680 points

    I've got a dev kit for this module - there's a jumper to switch HOLD_LDO1 from a connection to SYS to GND.  I thought this would switch the voltage at VLDO1 to 0V, but it seemed to have no effect.  Am I still missing something?  

  • 0 in reply to BuffaloEngineer
    TI__Genius 16870 points

    Is the AC on? Please note that when AC is valid the LDO and DCDC are on.

    HOLD_LDO & HOLD_DCDC Function Example

    1. Apply only BAT at ~3.6V then push & hold PWRBTN.
    2. Switch HOLD_LDO&HOLD_DCDC to VSYS.
    3. Release PWRBTN.
    4. Find that LDO and DCDC are both on.
    5. Switch HOLD_LDO to GND.
    6. Find that LDO turns off.

  • 0 in reply to Michael Green
    Intellectual 680 points

    So if I have PB_IN at GND, switching the voltage at HOLD_LDO and HOLD_DCDC will have no effect.

    If PB_IN is set to VSYS, switching the voltage at HOLD_LDO and HOLD_DCDC will turn the voltage converters on and off, but only if AC is floating (has no connection to external power).  

    If I intend to have an input that power cycles HOLD_LDO, I can have a pull up resistor to VSYS on HOLD_LDO1 and have PB_IN set to VSYS (but only when AC is not connected)?  

    Or is it a mistake to use any of these inputs for a push button reset?  

  • 0 in reply to BuffaloEngineer
    TI__Genius 16870 points

    Hi

    I am not really sure what your are trying to go for but, perhaps if I describe how it works that can help you.

    If PB_IN is LOW then, the LDO and DCDC are on.

    If the AC is in the valid AC voltage range then, the LDO and DCDC are on.

    You can toggle LDO and DCDC by toggling HOLD_LDO and HOLD_DCDC only when the battery is the source of power and PB_IN is high but, has been pressed at least once since power on.

    You may use I2C to turn on and off LDO or DCDC. You can also change the way LDO and DCDC stay on after PB_IN is pressed. (See the GUI or datasheet for details)