PMM Operation
204
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Power Management Module (PMM)
3.3
PMM Operation
It is important to understand some fundamental concepts beforehand.
3.3.1 Power Switch
A power domain gets its power supply via a power switch. The power switch creates a link between the
global core supply plane and the local switchable power domain supply. Each power domain uses multiple
power switches, which are daisy-chained together.
3.3.2 Power Domain State
Each core power domain can be in one of three states: Active, Idle, or Off.
In the
active
state, a power domain is fully powered with normal supply voltage.
In the
idle
state, all clocks to a power domain are turned off (driven low). The supply voltage is still
maintained at the normal level.
In the
off
state, a power domain is completely cut off from the power supply.
3.3.3 Default Power Domain State
The default state of each power domain, except for PD1, is controlled by TI during production testing via
programmation of individual bits within the reset configuration word in the TI-OTP sector of flash bank 0.
This allows each power domain to default to either the active state or the off state.
3.3.4 Disabling a Power Domain Permanently
TI can also permanently disable any power domain, except for PD1. This is also controlled by
programmation of individual bits within the reset configuration word in the TI-OTP sector of flash bank 0.
3.3.5 Changing Power Domain State
A domain can only change state when commanded by the application. Each domain has an associated 4-
bit key to define the intended power state. When the correct key is programmed, the PMM initiates the
sequence to transition that domain to the commanded state.
A power state transition is considered complete only when every single power switch for that domain has
switched over to the commanded state.
3.3.5.1
Turning a Power Domain Off
It is necessary to turn off all clocks going to a power domain before that domain can be powered down.
PMM contains the hardware interlocks to handle this. Each power domain has an associated memory-
mapped register which allows the application to turn off clocks to that power domain.
Steps to power down a domain with logic – PD2, PD3, PD4, PD5:
1. Write to the PDCLK_DISx register to disable all clocks to the power domain.
2. Write 0xA to the LOGICPDPWRCTRL0 register to power down each domain.
3. Poll for LOGICPDPWRSTATx.LOGICPDPWR_STATx to become “00”. The power domain is now
powered down.
A power domain with only SRAM macros does not have a clock input, so the sequence is shorter. This
applies to RAM_PD1, RAM_PD2 and RAM_PD3 power domains shown in
1. Write the correct key to the MEMPDONx register to power down the domain.
2. Poll for MEMPDPWRSTATx.MEMPDPWR_STATx to become “00”. The power domain is now powered
down.