Managing power consumption in automotive applications

AN4102

12/16

Doc ID 023129 Rev 1

3

Managing power consumption in automotive

applications

3.1

Low-power application description

The idea behind the low-power concept is that the application may be active for a small

percentage of the time to perform some of its dedicated tasks, but can be placed into an idle

mode for a remaining period when activity from the MCU is not required. This is especially

important at a time where, in the electronics world, energy saving is becoming more and

more important. For example, 8-bit microcontrollers in the automotive domain are

sometimes dedicated to a single task and do not need to be active 100% of the time to

perform their operation (wiper systems, rain sensors, door mechatronics, etc…). The idea is

to be able to switch the microcontroller into a low-power mode for the maximum time to save

energy. Figure 7 shows a graphical representation of a low-power application over time. The

activity of the MCU can be broken down into three phases.

●

MCU active is the time during which tasks from the microcontroller are performed.

●

MCU idle is the time during which neither MCU activity nor resources are required.

●

MCU wakeup is the time necessary for the microcontroller to switch from the idle to the

active state.

Figure 7.

Typical sequence of a low-power application

If we assume that the power consumption of these three phases is equivalent to:

●

●

●

calculated with the following formula.

MCU active

MCU active

MCU wakeup

MCU wakeup

t

MCU idle