ATmega48/88/168
Table 29-2. Additional Current Consumption (percentage) in Active and Idle mode
Additional Current consumption
compared to Active with external
clock
Additional Current consumption
compared to Idle with external clock
(see Figure 29-7 and Figure 29-8)
PRR bit
PRUSART0
PRTWI
(see Figure 29-1 and Figure 29-2)
3.3%
4.8%
4.7%
2.0%
1.6%
6.1%
4.9%
18%
26%
25%
11%
8.5%
33%
26%
PRTIM2
PRTIM1
PRTIM0
PRSPI
PRADC
It is possible to calculate the typical current consumption based on the numbers from Table 2 for
other VCC and frequency settings than listed in Table 1.
29.3.0.1
29.3.0.2
29.3.0.3
Example 1
Example 2
Example 3
Calculate the expected current consumption in idle mode with USART0, TIMER1, and TWI
enabled at VCC = 3.0V and F = 1MHz. From Table 2, third column, we see that we need to add
18% for the USART0, 26% for the TWI, and 11% for the TIMER1 module. Reading from Figure
3, we find that the idle current consumption is ~0,075mA at VCC = 3.0V and F = 1MHz. The total
current consumption in idle mode with USART0, TIMER1, and TWI enabled, gives:
ICCtotal ≈ 0,075mA • (1 + 0,18 + 0,26 + 0,11) ≈ 0,116mA
Same conditions as in example 1, but in active mode instead. From Table 2, second column we
see that we need to add 3.3% for the USART0, 4.8% for the TWI, and 2.0% for the TIMER1
module. Reading from Figure 1, we find that the active current consumption is ~0,42mA at VCC
=
3.0V and F = 1MHz. The total current consumption in idle mode with USART0, TIMER1, and
TWI enabled, gives:
ICCtotal ≈ 0,42mA • (1 + 0,033 + 0,048 + 0,02) ≈ 0,46mA
All I/O modules should be enabled. Calculate the expected current consumption in active mode
at VCC = 3.6V and F = 10MHz. We find the active current consumption without the I/O modules
to be ~ 4.0mA (from Figure 2). Then, by using the numbers from Table 2 - second column, we
find the total current consumption:
ICCtotal ≈ 4,0mA • (1 + 0,033 + 0,048 + 0,047 + 0,02 + 0,016 + 0,061 + 0,049) ≈ 5,1mA
323
2545M–AVR–09/07
ATMEL [ ATMEL ]
