ATMEGA8_08 Datasheet, PDF(36/308 Page) ATMEL Corporation – 8-bit with 8K Bytes In-System Programmable Flash

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ATMEGA8_08 Datasheet, PDF (36/308 Pages) ATMEL Corporation – 8-bit with 8K Bytes In-System Programmable Flash

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Brown-out Detector

Internal Voltage

Reference

Watchdog Timer

Port Pins

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

Brown-out Detector is enabled by the BODEN Fuse, 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 âBrown-out Detectionâ 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 Detector, 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 consuming 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 âInternal Volt-

age Referenceâ on page 42 for details on the start-up time.

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

Watchdog Timer is enabled, 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 consump-

tion. Refer to âWatchdog Timerâ on page 43 for details on how to configure the Watchdog Timer.

When entering a sleep mode, all port pins should be configured to use minimum power. The

most important thing is then to ensure that no pins drive resistive loads. In sleep modes where

the both the I/O clock (clkI/O) and the ADC clock (clkADC) are stopped, the input buffers of the

device will be disabled. This ensures that no power is consumed by the input logic when not

needed. In some cases, the input logic is needed for detecting wake-up conditions, and it will

then be enabled. Refer to the section âDigital Input Enable and Sleep Modesâ on page 55 for

details on which pins are enabled. If the input buffer is enabled and the input signal is left floating

or have an analog signal level close to VCC/2, the input buffer will use excessive power.

36 ATmega8(L)

2486TâAVRâ05/08

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