ATMEGA6450-16AI(2004) データシートの表示（PDF） - Atmel Corporation

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ATMEGA6450-16AI
(Rev.:2004)

8-bit Microcontroller with In-System Programmable Flash

Atmel Corporation 

Minimizing Power

Consumption

Analog to Digital Converter

Analog Comparator

Brown-out Detector

Internal Voltage Reference

Watchdog Timer

• Bit 2 - PRSPI: Power Reduction Serial Peripheral Interface

Writing logic one to this bit shuts down the Serial Peripheral Interface by stopping the

clock to the module. When waking up the SPI again, the SPI should be re-initialized to

ensure proper operation.

• Bit 1 - PRUSART: Power Reduction USART

Writing logic one to this bit shuts down the USART by stopping the clock to the module.

When waking up the USART again, the USART should be re-initialized to ensure proper

operation.

• Bit 0 - PRADC: Power Reduction ADC

Writing logic one to this bit shuts down the ADC. The ADC must be disabled before shut

down. The analog comparator cannot use the ADC input MUX when the ADC is shut

down.

Note: The Analog Comparator is disabled using the ACD-bit in the “Analog Comparator Control

and Status Register – ACSR” on page 189.

There are several possibilities to consider when trying to minimize the power consump-

tion in an AVR controlled system. In general, sleep modes should be used as much as

possible, and the sleep mode should be selected so that as few as possible of the

device’s functions are operating. All functions not needed should be disabled. In particu-

lar, the following modules may need special consideration when trying to achieve the

lowest possible power consumption.

If enabled, the ADC will be enabled in all sleep modes. To save power, the ADC should

be disabled before entering any sleep mode. When the ADC is turned off and on again,

the next conversion will be an extended conversion. Refer to “Analog to Digital Con-

verter” on page 193 for details on ADC operation.

When entering Idle mode, the Analog Comparator should be disabled if not used. When

entering ADC Noise Reduction mode, the Analog Comparator should be disabled. In

other sleep modes, the Analog Comparator is automatically disabled. However, if the

Analog Comparator is set up to use the Internal Voltage Reference as input, the Analog

Comparator should be disabled in all sleep modes. Otherwise, the Internal Voltage Ref-

erence will be enabled, independent of sleep mode. Refer to “Analog Comparator” on

page 189 for details on how to configure the Analog Comparator.

If the Brown-out Detector is not needed by the application, this module should be turned

off. If the Brown-out Detector is enabled by the BODLEVEL Fuses, it will be enabled in

all sleep modes, and hence, always consume power. In the deeper sleep modes, this

will contribute significantly to the total current consumption. Refer to “Brown-out Detec-

tion” on page 40 for details on how to configure the Brown-out Detector.

The Internal Voltage Reference will be enabled when needed by the Brown-out Detec-

tion, the Analog Comparator or the ADC. If these modules are disabled as described in

the sections above, the internal voltage reference will be disabled and it will not be con-

suming power. When turned on again, the user must allow the reference to start up

before the output is used. If the reference is kept on in sleep mode, the output can be

used immediately. Refer to “Internal Voltage Reference” on page 43 for details on the

start-up time.

If the Watchdog Timer is not needed in the application, the module should be turned off.

If the Watchdog Timer is enabled, it will be enabled in all sleep modes, and hence,

36 ATmega325/3250/645/6450

2570A–AVR–09/04

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