prcm-001
Without DVFS
P
o
w
e
r
1
Execution time(s)
P
o
w
e
r
4
Execution time(s)
0.12
With DVFS
3
2
1
4
3
2
1
Average energy used
(over 4 seconds)
= 0.25 J
Average energy used
(over 4 seconds)
= 0.12 J
Public Version
Introduction to Power Managements
www.ti.com
3.1
Introduction to Power Managements
This introduction contains the following information:
•
Requirement and goal of power management in mobile devices
•
State-of-the-art power-management techniques for maximizing battery life for mobile devices
•
Essential architectural building blocks for power management
•
Overview of the device power-management architecture
3.1.1 Goal of Power Management
Power management (efficient use of the available limited battery resources of a mobile device) is one of
the most important design aspects of any mobile system. It imposes strong control over limited available
power resources to ensure that they function for the longest possible time.
The device architecture ensures maximum performance for user satisfaction (audio/video support) while
offering versatile power-management techniques for maximum design flexibility, depending on application
requirements.
3.1.2 Power-Management Techniques
The following sections describe the state-of-the-art power-management techniques supported by the
device.
NOTE:
The values in
through
, which show power-management techniques,
are hypothetical only. They do not represent valid test results on the device.
3.1.2.1
Dynamic Voltage and Frequency Scaling
Dynamic voltage and frequency scaling (DVFS) reduces the device voltage and frequency by minimizing
the idle time of the system. The DVFS technique uses dynamic selection of the optimal operating
frequency and voltage to let a task be performed in the required amount of time. This reduces the active
power consumption (power consumed while executing a task) of the device while still meeting task
requirements.
compares energy consumption with and without DVFS.
Figure 3-1. Comparison of Energy Consumption With/Without DVFS
shows the DVFS technique by comparing a process executed at maximum frequency and
operating voltage without applying DVFS to the same process executed at optimal frequency and voltage
using DVFS, based on the task requirements. If a task that must terminate in 4 seconds is performed at
226
Power, Reset, and Clock Management
SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated