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TPS65381A-Q1: Charge pump pins and disabling reset from watchdog

Diego Rocha
Prodigy 160 points
Part Number: TPS65381A-Q1

Hola que tal.

Tengo un par de preguntas acerca del comportamiento de este IC en algunos modos de falla:

1. En la hoja de datos se recomienda colocar un capacitor (>=100nF) entre VCP y VBATP,

a. ¿que pasa con el PMIC si este capacitor falla en corto?

b. ¿que pasa con el PMIC si este capacitor falla en abierto?

2. En la hoja de datos se recomienda colocar un capacitor (>=10nF) entre CP1 y CP2,

a. ¿que pasa con el PMIC si este capacitor falla en corto?

b. ¿que pasa con el PMIC si este capacitor falla en abierto?

  • 0
    TI__Genius 17380 points
    Hola Diego,

    He asignado esta publicación al experto en dispositivos, sin embargo, él no habla español. ¿Puedes traducir la publicación al inglés?

    Hello Diego,

    I have assigned this post to the device expert, however he does not speak Spanish. Are you able to translate the post into English?
  • 0 in reply to Kevin LaRosa
    Prodigy 160 points

    Yes, thank you.

    I have some questions about the behavior of this IC in some failure modes:

    1. In the data sheet it is recommended to place a capacitor (> = 100nF) between VCP and VBATP,

    a. What happens to the PMIC if this capacitor fails in short?

    b. What happens to the PMIC if this capacitor fails openly?

    2. In the data sheet it is recommended to place a capacitor (> = 10nF) between CP1 and CP2,

    a. What happens to the PMIC if this capacitor fails in short?

    b. What happens to the PMIC if this capacitor fails openly?


    Add:
    3. What happens to the PMIC if the resitor of RSTEXT pin fails openly?
    4. Can the Watchdog function be disabled to prevent an MCU from being reset (due to the NRES pin) if desired and prevent the PMIC from entering the RESET state?


    Diego Rocha.

  • 0 in reply to Diego Rocha
    TI__Mastermind 20590 points

    Hi Diego,

    In addition to the datasheet you can also refer to the design check list which helps with what pins need which passive components to function. This design checklist and other application notes are found at: www.ti.com/.../technicaldocuments

    A1) It is not recommended but required to put the capacitors for the charge pump between VCP (charge pump) and VBATP to get the overdrive for the FETs of the device.
    A1a and A1b) Please see the Pin-FMA which is included in the safety analysis report (SAR) for the device for all details, in simple terms without the charge pump capacitors the device doesn't work because overdrive voltage needed will not be available from the charge pump.
    To request the SAR (under NDA) please click on the: More Information Functional Safety Documentation is available. Request now button on the product folder on www.ti.com/.../TPS65381A-Q1


    A2) It is not recommended but required to put the capacitors for the charge pump between CP1 (charge pump 1) and CP2 (charge pump 2) to get the overdrive for the FETs of the device.
    A2a and A2b) Please see the Pin-FMA which is included in the safety analysis report (SAR) for the device for all details, in simple terms without the charge pump capacitors the device doesn't work because overdrive voltage needed will not be available from the charge pump.

    A3) Please see the Pin-FMA which is included in the safety analysis report (SAR) for the device for all details, in simple terms without the resistance to gnd on this pin the device will stay in RESET state indefinitely and not continue the power up or RESET to DIAGNOST state transitions.

    A4) The reset from watchdog function is disabled by default on power up initialization. The MCU software must synconize to the watchdog in the TPS device and decrement the WD_FAIL_CNT and then enable reset events from the watchdog by using the WD_RST_EN bit. If no action is taken at power up by the MCU the watchdog counters are free-running and the WD_FAIL_CNT will increment but no RESET state transition will occur. Note, the ENDRV safing output cannot be made low until the WD_FAIL_CNT is < 5.

    Please let us know if you have further questions.

  • 0 in reply to Scott Monroe
    Prodigy 160 points
    Thank you Scott Monroe.
    I already review all documetation in www.ti.com/.../technicaldocuments

    I already requested the safety documentation.

    You are right these capacitors are required for the Charge-Pump (it was my mistake: I meant that the value of these is a recommended value), with your answer I was clear every point, even so, I hope to get the safety documentation for review more details about it.