RM0319 datasheet(329/368 Pages) STMICROELECTRONICS

329 / 368 page

RM0319

Power, reset and clock control

Doc ID 022640 Rev 3

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30.3.3

Combining frequency scalling and clock techniques

In NORMAL state, the best active power saving is obtained by combining the power

management techniques previously described.

These techniques reduce the power consumption of a device allowing a fast response to a

critical task (that can be performed always at maximum frequency, if needed).

30.3.4

Statically frequency selection and clock switching OFF

With this technique, you can define statically, based on performance defined in the

manufacturing process, the frequency and activate only the modules requested by the

application.

This technique is easier from the designer’s point of view for software development and

offers a well known consumption. It is recommended that when the performance required is

without critical task, it is sufficient to guarantee an average power computation.

This technique should be applied when a constant consumption is requested by the system.

It is useful when USB ports are not requested switch of USB PLL (PLL3) and peripheral

clock could be attached to PLL1, with the right prescaler.

Also PLL2 should be OFF in synchronous mode.

Flash serial (SMI)

IrDA

PLL1

Internal ROM

JPEG codec

PLL2

DMA

I2C

PLL3

Table 118.

Modules supporting DCS technique

Module

RM0319 数据表(PDF) 329 Page - STMicroelectronics