USS Power States
461
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Universal USS Power Supply (UUPS)
new measurement.
9. If the PSQ internal timer reaches its time-out limit before the PLL_LOCK signal is asserted,
UUPSRIS.PTMOUT is set to 1. The time-out is not programmable and can vary depending on the PLL
output clock frequency. The maximum delay is 160 µs plus the configured "holdoff time" (~300us max).
CAUTION
The
application
must
turn
on
the
USSXT
oscillator
(HSPLLUSSXTLCTL.OSCEN = 1) and wait for a sufficient time to let the
oscillator start (this depends on the crystal or resonator characteristics) before
powering up the USS module. The USSXT oscillator is not controlled by the
PSQ. The PSQ assumes that the oscillator output is already available and
stable in frequency and amplitude).
19.3 USS Power States
The following power states are supported by the UUPS module.
•
OFF:
The USS module is powered off (UUPSCTL.UPSTATE = 0).
•
TRANSITION:
The USS module is in transition state (UUPSCTL.UPSTATE = 2).
•
READY:
The USS module is fully powered up and ready (UUPSCTL.UPSTATE = 3).
•
STANDBY:
The USS module is powered off, but the SREF remains on for fast wakeup
(UUPSCTL.UPSTATE = 1).
•
TIMEOUT:
The power-up sequence is taking more than expected time. The USS module goes back to
OFF state and the PTMOUT (power time-out) interrupt is generated if enabled (UUPSCTL.UPSTATE
bits = 0).
Table 19-1. USS Power State
Power State
State Register
(UUPSCTL.UPSTATE)
Description
OFF
0
The USS module is fully powered off.
TRANSITION
2
In transition. A new trigger to the PSQ is ignored.
READY
3
The USS module is fully powered up.
STANDBY
1
The USS module is powered off, but SREF is enable for fast wakeup.
TIMEOUT
0
The USS power-up sequence has not been properly ended. The USS module goes
back to OFF state and UUPSRIS.PTMOUT is set to 1.
Note: A time-out should not happen during normal operating conditions. Make sure that
the USSXT oscillator is enabled and working properly.