ATA8741 ATMEL Corporation, ATA8741 Datasheet - Page 52

• Manufacturer Part Number: ATA8741
• Manufacturer: ATMEL Corporation

15.7
15.7.1
15.7.2
15.7.3
15.7.4
15.7.5
15.7.6
52
Minimizing Power Consumption
ATA8741
Analog to Digital Converter
Analog Comparator
Brown-out Detector
Internal Voltage Reference
Watchdog Timer
Port Pins
There are several issues to consider when trying to minimize the power consumption 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 particular, 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 dis-
abled before entering any sleep mode. When the ADC is turned off and on again, the next
conversion will be an extended conversion. See
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 the 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 dis-
abled in all sleep modes. Otherwise, the Internal Voltage Reference will be enabled,
independent of sleep mode. See
ure the Analog Comparator.
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 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. See
configure the Brown-out Detector.
The Internal Voltage Reference will be enabled when needed by the Brown-out Detection, 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. See
Reference” on page 60
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. See
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
both the I/O clock (clk
will be disabled. This ensures that no power is consumed by the input logic when not needed. In
“Watchdog Timer” on page 60
I/O
for details on the start-up time.
) and the ADC clock (clk
“Analog Comparator” on page 150
“Brown-out Detection” on page 59
for details on how to configure the Watchdog Timer.
ADC
“Analog to Digital Converter” on page 154
) are stopped, the input buffers of the device
for details on how to config-
for details on how to
“Internal Voltage
9140B–INDCO–07/09
for