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TPS65950 Sequence Start

Suresh Samynathan
Intellectual 360 points
Other Parts Discussed in Thread: TPS65950

I’m trying to make the TPS65950 to Wait-ON state but the device is automatically restarting after writing into DEVOFF register.

 

The design is as below

 

PWRON – Pulled up to VBAT

VAC and VBUS both are supplied 5.0V through USB

AC Charger circuit present

 

When the VAC is not supplied and VBUS alone supplied, the device is not restarting till the pulse is given to PWRON.

 

After making the STARTON_CHG bit to 0 in CFG_P1_TRANSITION, CFG_P2_TRANSITION and CFG_P3_TRANSITION registers, the device is not restarting after writing into DEVOFF register when the VAC is present.

 

Does this mean if the VAC is present, the device will start automatically in the default configuration.

  • 0
    TI__Prodigy 630 points

    Hi,

        The observation seen is an expected one. VAC detection is LEVEL sensitive whereas USB/VBUS detection is EDGE sensitive. Hence, if VAC is plugged, device will automatically re-start as defalut value of STARTON_CHG is 1.

    Kartik

  • 0 in reply to Kartik Sudarshana11777
    Intellectual 360 points

    Hi,

    To start the TPS in master mode, one of the option is providing PWRON Pulse for minimum of 31.25ms. We have tested and found high to low transition of PWRON is starting the sequence. The PWRON is still maintained in LOW state and the TPS is not powering OFF. This indicates the PWRON need not go to high after starting.

    If the TPS is ON and PWRON is pressed for more than 8 seconds then the TPS will go to power OFF. Pressing the PWRON for more than 8 seconds during start does not make the entering into power OFF mode. Is this expected behaviour.

  • 0 in reply to Suresh Samynathan
    TI__Prodigy 630 points

    Hi,

        Regarding the first point, yes, for starting the CHIP, PWRON need not go high. If it is maintained LOW, TPS will turn ON.

    The behavior you are seeing is an expected one. By default, Bit 6 ( STOPON_PWRON ) of the register Px_SW_EVENTS is "0". This means that pressing it for 8 seconds will NOT turn OFF TPS.

    In your case when TPS is ON and PWRON is pressed for more than 8 sec, you are seeing that TPS goes to POWER OFF. Here, you must have programmed the bit STOPON_PWRON to "1" before pressing PWRON and hence you are seeing a POWER OFF. Could  you please confirm?

    Kartik