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Power down and power sequencing mode

robert kovacic
Prodigy 30 points
Part Number: MCT8316Z-Q1
Other Parts Discussed in Thread: MCT8316Z, MCT8316ZTEVM, DRV8316REVM

Hi,

can internal buck converter or AVDD output in MCT8316Z be used for powering external support microcontroller without external nSLEEP pin control? On MCT8316Z, nSLEEP pin has internal pulldown, which will during the system start up hold part in sleep mode where, if we understand correctly, AVDD linear regulator and also internal buck does not work. This mean that local CPU will not get power and can not pull nSLEEP pin up if CPU is connected to AVDD as shown on Figure 9-1 or 9-2 in the datasheet. On demo board power supply is provided externally from USB so it does not have this problem.
What would be suggestion to have sucessfull start over whole temperature range without using additional external converter from VM voltage to 3.3V? Simple high resistance pull up from nSLEEP to VM, and count on internal ESD diodes clamping to AVDD voltage?

Another question:
Controller has power sequencing mode where AVDD voltage can be generated from buck output voltage. This is controlled via BUCK_PS_DIS bit. How this work on hardware set up part MCT8316ZT-Q1? Is power sequencing always on or it is not supported?

Regards,

Robert

  • 0
    TI__Mastermind 26046 points

    Hi Robert,

    robert kovacic said:
    can internal buck converter or AVDD output in MCT8316Z be used for powering external support microcontroller without external nSLEEP pin control?

    Yes, power sequencing is automatically enabled when the buck voltage is 5.0V or 5.7V (selected through VSEL_BK pin on MCT8316Z0T, or BUCK_SEL = 10b or 11b and BUCK_PS_DIS = 0 on MCT8316Z0R).

    In a typical application, nSLEEP needs to be pulled up to 3.3V through some external source that powers up before the MCT8316Z powers up in order for the MCT8316Z to power up with the buck regulator and with power sequencing. On the MCT8316ZTEVM, nSLEEP is pulled to 3.3V via the external MCU, which can be powered on separately before VM is applied. If VM is applied before the nSLEEP goes high, the internal pulldown takes over and the device is in sleep mode and the internal buck is disabled. This behavior has been confirmed on the EVM.

    robert kovacic said:
    What would be suggestion to have sucessfull start over whole temperature range without using additional external converter from VM voltage to 3.3V? Simple high resistance pull up from nSLEEP to VM, and count on internal ESD diodes clamping to AVDD voltage?

    How we solved this problem before on the DRV8316REVM (which also uses nSLEEP and includes an internal buck regulator) is we use a 3.3V Zener clamp diode from VM with a pullup resistor so that nSLEEP can still be controlled via a GPIO, but it is now pulled up to 3.3V. See schematic below. 

    robert kovacic said:
    Controller has power sequencing mode where AVDD voltage can be generated from buck output voltage. This is controlled via BUCK_PS_DIS bit. How this work on hardware set up part MCT8316ZT-Q1? Is power sequencing always on or it is not supported?

    Power sequencing is always on as long as the buck voltage is 5.0V or 5.7V. 

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    Prodigy 30 points

    Hi Aaron,

    Thanks for your feeback, this resolved my issue.