RM0312 datasheet(67/275 Pages) STMICROELECTRONICS

67 / 275 page

DocID022352 Rev 3

67/275

RM0312

Power management

By default, after a system or power reset, the microcontroller is in Run mode. In this mode

the CPU is clocked by fMASTER and executes the program code, while the system clock to

all peripherals is gated off by the peripheral clock gating system.

While in Run mode, still keeping the CPU running and executing code, the application has

several ways to reduce power consumption, such as:

•

Slowing down the system clock

•

Gating the clocks to individual peripherals when they are unused

•

Switching off any unused analog functions

However, when the CPU does not need to be kept running, three dedicated low power

modes can be used:

•

Wait (wait for interrupt and wait for event)

•

Active-halt

•

Halt

One of these three modes can be selected and configured to obtain the best compromise

between lowest power consumption, fastest startup time and available wakeup sources.

9.1

General considerations

Low power consumption features are generally very important for all types of application for

energy saving. Ultra low power features are especially important for mobile applications to

ensure long battery lifetimes. This is also crucial for environmental protection.

In a silicon chip there are two kind of consumption:

•

Static power consumption which is due to analog polarization and leakage.

Consumption due to leakage is so small that it is only significant in Halt and Active-halt

modes (Section 9.4: Low power modes).

•

Dynamic power consumption which comes from running the digital parts of the chip.

It depends on VDD, clock frequency and load capacitors.

In a microcontroller device the consumption depends on:

•

VDD supply voltage

•

MCU size or number of digital gates (leakages and load capacitors)

•

Clock frequency

•

Number of active peripherals

•

Available low power modes and low power levels

Device processing performance is also very important, as this allows the application to

minimize the time spent in Run mode and maximize the time in Low power mode.

Using the MCU’s flexible power management features, you can obtain a range of significant

power savings while the system is running or able to resume operations quickly.

RM0312 数据表(PDF) 67 Page - STMicroelectronics

RM0312 数据表(HTML) 67 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载