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TPS65217: TPS65217C - Purpose of Pin 25 (PB_IN)

Stephen Gilbert52
Prodigy 140 points
Part Number: TPS65217
Other Parts Discussed in Thread: TPS65216

What is the purpose of the PB_IN pin on the TPS65217C? We are planning on using the devise with the AM335X Sitara device and the definition of the pin from the TPS65217 data sheet only states:

"Push-button monitor input. This pin is typically connected to a momentary switch to ground. This

pin is an active-low input."

When would the pin need to be momentarily connected to ground in the application with the AM335X and what will temporarily connecting this pin to ground cause to happen?

Thank you.

Stephen Gilbert

Staff Engineer

NORTHROP GRUMMAN

Mission Systems

5000 Bradford Blvd Suite 100

Huntsville, AL 35805

Phone: (256) 327-6772

stephen.gilbert@ngc.com

  • 0
    TI__Mastermind 30280 points

    Stephen,

    You can refer to section 8.3.3 Push-Button Monitor (PB_IN) on page 23 of the TPS65217 datasheet for details on the operation of the PB_IN pin, which states

    "The push-button monitor has two functions.  The first is to power-up the device from the OFF or SLEEP state when a falling edge is detected on the PB_IN pin. The second is to power cycle the device when the PB_IN pin is held low for more than 8 s."


    You can also see in Figure 24. Global State Diagram on page 39 that the wake-up events that allow the device to go from the SLEEP or the OFF state to the ACTIVE state include a falling edge on the PB_IN pin. However, since the 2nd function of the PB_IN pin is to power cycle the device if the push button is held low for >8s, then it is clear that you cannot simply tie the PB_IN pin to GND or the system will reset every 8+1=9s (8s plus the 1s min off time wait).

    If the only power supply in the system is a battery (BAT pins), then press the push-button is required to power-on the system. If AC is the only power supply in the system, the device will power-on automatically when AC power is applied, but you cannot use the SLEEP state for power-saving without a push-button to return to the ACTIVE state.

    I hope this clears up any confusion you may have regarding the PB_IN pin of the TPS65217.

    If you are planning on using the AM335x in a system that does not have a battery and will not use the WLED driver of the TPS65217C device, then may I recommend that you consider using the TPS65216?