PSQ (Power
Sequencer)
USS LDO
HSPLL
PSQ_LDOUP
PSQ
_
SR
EF
R
EQ
BIAS_REF
SREF
UUPS
VBG
IREF_MOD
IREF_PLL
IBIAS
VREF
PSQ_PLLUP
ENABLE
PLL_CLK
LDO_OUT
L
D
O
_
R
D
Y
SDHS
PL
L
_
L
O
C
K
USS_PWRREQ
00
01
10
11
UUPSCTL.
USSPWRUP
UUPSCTL.
USSPWRUPSEL
2
External Signal
External Signal
External Signal
UUPSCTL.
SWRST
USS_SWRST
USS Power-up Sequence
460
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Universal USS Power Supply (UUPS)
Figure 19-2. UUPS Block Diagram
The signal names in
are for information only to show how each block is connected inside the
UUPS module. These signals are not under user control.
NOTE:
Naming convention for register names and bit fields:
•
UUPS registers: RegisterName or RegisterName.BitField
•
Other module registers: ModuleNameRegisterName or
ModuleNameRegisterName.BitField
19.2 USS Power-up Sequence
The Power Sequencer (PSQ) block controls the USS module power-up and power-down sequences. The
PSQ powers up the USS module when the USS_PWRREQ signal is asserted (see
). The
USS_PWRREQ signal can be generated from four different sources. When
UUPSCTL.USSPWRUPSEL = 0, writing 1 to UUPSCTL.USSPWRUP generates the USS_PWRREQ
signal and starts the USS power-up sequences. The other sources may or may not be available; see the
device-specific data sheet for the internal signal sources (search for UUPSCTL.USSPWRUPSEL). The
power states of the USS module can be monitored by reading UUPSCTL.UPSTATE.
The order of the USS power-up sequence is:
1. The USS_PWRREQ is asserted when the USS module is powered off (UUPSCTL.UPSTATE = 0,
indicating that the USS module is in OFF state).
2. The PSQ sends a request to the shared reference (SREF) to generate VBG and starts an internal
timer (UUPSCTL.UPSTATE = 2, indicating that the USS power state is in transition).
3. The PSQ enables the BIAS_REF block when the VBG is ready (UUPSCTL.UPSTATE = 2).
4. The PSQ turns on the USS_LDO when the required reference voltages and currents are ready
(UUPSCTL.UPSTATE = 2).
5. The PSQ waits for the LDORDY, signal which can be monitored by reading UUPSCTL.LDORDY
(UUPSCTL.UPSTATE = 2).
6. The PSQ enables the HSPLL module when LDORDY = 1 (UUPSCTL.UPSTATE = 2).
7. The PSQ waits for the PLL_LOCK signal from the HSPLL module. The PLL_LOCK can be monitored
by reading HSPLLCTL.PLL_LOCK (UUPSCTL.UPSTATE = 2).
8. The PSQ sets UUPSCTL.UPSTATE = 3 to indicate that the USS is fully powered and ready to start a