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TPS65381A-Q1: Can [WR_CAN_STBY] SPI command let TPS65381A-Q1 to standby status?

Part Number: TPS65381A-Q1

Hi, all

  I use TPS65381A-Q1 with RM46L852 microcontroller,  In the begin, I use IGN to switch on TPS65381A-Q1 and set [IGN_PWRL] bit  with 1 ,  so if the IGN pin go low,  the MCU will not be power down.

 My question is if I send [WR_CAN_STBY] SPI command throgh SPI line to TPS,   will the TPS65381A-Q1 go to standby status?

Best Regards

Daimb

  • Hi,

    I have assigned your request to concerned Applications Engineer and we will get back to you as soon as possible. Please note that this is vacation time in US and there may be some delay in answering your question.

    Regards,

    Murthy
  • In reply to Krishnamurthy Hegde:

    Hi,

    I checked the below conditions on the EVM.
    - Device wake up through IGN pin and set IGN_PWRL=1 and when i removed high on IGN pin, device stayed alive. When I set IGN_PWRL=0 and removed high on IGN pin, device went to standby.
    - Device wake up through CANWU pin and removed CANWU high and send WR_CAN_STBY=0, device went to standby.
    - As soon as soon as CANWU is asserted, IGN_PWRL bit is cleared and we cannot set this bit if wake up is through CANWU pin.
    Above are normal and expected operation.

    But if I power up through high on IGN pin and set IGN_PWRL=1 and remove IGN pin voltage (IGN low) and tried to set WR_CAN_STBY=0, device did not shutdown. If I understand your question correctly, this is what you are trying to do. So, based on my experiment, this cannot be done. Based on the datasheet state machine, one condition for standby mode is: (IGN = 0 & IGN_PWRL=0 & CANWU_L = 0) and this means, IGN_PWRL has to be "0" for going in to standby mode.

    However, I will check with our expert (He is on vacation and comes back next week) on this device and provide you further feedback. Also

    Regards,

    Murthy
  • In reply to Krishnamurthy Hegde:

    Dear Mruthy:

     thank your kind response. 

    So it seemed the only way to let TPS go to Standby status is :

        let Watchdog do some error response to TPS  ->   TPS go to reset status ->  TPS go to diagnoist status ->  clear IGN_PWRL bit ->   TPS go to standby status

    isn't it ?

    Is there any simple method ( e.g.   one or two steps)   to let TPS go to standby status ?

    Best regards

    Daimb

     

  • In reply to user5102395:

    Hi Daimb,

    If you don't set IGN_PWRL=1 in diagnostic state, when the IGN pin voltage goes down, device will enter standby. It will be only hardware controlled power down then.

    Or

    If you use CANWU pin for wakeup, you can bring the device in standby using WR_CAN_STBY register write in any state. When you do wake up through CANWU pin, device powers up and device stays on even when you remove CANWU signal. If you then write WR_CAN_STBY=0, device will enter standby state.

    Wake up/standby control through CANWU / WR_CAN_STBY will not work for you?

    Regards,

    Murthy
  • In reply to Krishnamurthy Hegde:

    seemed it works for me . thanks very much.

    best Regards,
    Daimb
  • In reply to user5102395:

    Hi Daimb,

    the last summary is correct.  There are 2 wake up sources.  If either of them remains HIGH you cannot go to STANDBY state.  IGN is normally for automotive ignintion and is reverse protected to -7V and has a longer deglitch for higher noise immunity.  The other is CANWU which is normally used with the INH pin of a 14 pin CAN XCVR but has only negative protection to -0.3V, but CANWU is automatically latched on wake up request.  Either one can be used to wake up the device, but for latched wake up CANWU has less constraints to then shut the device off:  CANWU pin must be low level and then send WR_CAN_STBY command, even if WR_CAN_STBY is sent and the CANWU pin (or IGN pin) is high the device will not go to STANDBY but immediately re-power up through RESET to DIAGNOSTIC state.  The WR_CAN_STBY command as outlined above is only for use with wake up from CANWU pin.  Using IGN pin with IGN_PWRL is more complicated. 

    Best Regards,

    Scott

  • In reply to Scott Monroe:

    HI, Scott

    thank your response, there are many valable information for me.

    Best Regards
    Daimb