Figure 6-9 depicts the power sequencing requirements for internal VREG mode. The values for
all the parameters indicated can be found in Power Management Module Electrical Data and Timing.
- For Power Up:
- VDDIO (that is, the 3.3-V
rail) should come up with the minimum slew rate specified.
- The Internal VREG powers
up after the I/O monitors (I/O POR and I/O BOR) are released.
- After the times specified
by VDDIO-MON-TOT-DELAY and VXRSN-PU-DELAY, XRSn
will be released and the device starts the boot-up sequence.
There is an additional delay between XRSn releasing (that is, going
high) and the boot-up sequence starting. See Figure 6-7.
- The I/O BOR monitor has
different release points during power up and power down.
- For Power Down:
- The only requirement on
VDDIO during power down is the slew rate.
- The I/O BOR monitor has
different release points during power up and power down.
- The I/O BOR tripping will
cause XRSn to go low after VXRSN-PD-DELAY and also power down
the Internal VREG.
Note: The All Monitors Release
Signal is an internal signal.
Note: If there is an external circuit
driving XRSn (for example, a supervisor), the boot-up sequence does not start until
the XRSn pin is released by all internal and external sources.