358
8025I–AVR–02/09
ATmega48P/88P/168P/328P
27.2.3 Supply Current of IO Modules
The tables and formulas below can be used to calculate the additional current consumption for
the different I/O modules in Active and Idle mode. The enabling or disabling of the I/O modules
are controlled by the Power Reduction Register. See ”Power Reduction Register” on page 42 for
details.
It is possible to calculate the typical current consumption based on the numbers from Table 27-4
on page 358 for other V
CC
and frequency settings than listed in Table 27-3 on page 358.
Example Calculate the expected current consumption in idle mode with TIMER1, ADC, and SPI enabled
at V
CC
= 2.0V and F = 1MHz. From Table 27-4 on page 358, third column, we see that we need
to add 17.0% for the TIMER1, 17.6% for the ADC, and 17.5% for the SPI module. Reading from
Figure 27-52 on page 355, we find that the idle current consumption is ~0.055 mA at V
CC
= 2.0V
and F = 1MHz. The total current consumption in idle mode with TIMER1, ADC, and SPI enabled,
gives:
Table 27-3. Additional Current Consumption for the different I/O modules (absolute values)
PRR bit Typical numbers
V
CC
= 2V, F = 1MHz V
CC
= 3V, F = 4MHz V
CC
= 5V, F = 8MHz
PRUSART0 4.12 uA 26.7 uA 108.3 uA
PRTWI 8.96 uA 58.6 uA 238.2 uA
PRTIM2 9.94 uA 64.1 uA 256.3 uA
PRTIM1 8.81 uA 56.9 uA 227.0 uA
PRTIM0 2.29 uA 15.5 uA 62.3 uA
PRSPI 8.31 uA 56.8 uA 260.4 uA
PRADC 9.27 uA 58.4 uA 230.8 uA
Table 27-4. Additional Current Consumption (percentage) in Active and Idle mode
PRR bit
Additional Current consumption
compared to Active with external
clock (see Figure 27-47 on page
353 and Figure 27-48 on page
353)
Additional Current consumption
compared to Idle with external
clock (see Figure 27-52 on page
355 and Figure 27-53 on page
356)
PRUSART0 1.3% 8.0%
PRTWI 2.9% 17.6%
PRTIM2 3.2% 19.2%
PRTIM1 2.8% 17.0%
PRTIM0 0.8% 4.6%
PRSPI 3.0% 17.5%
PRADC 2.9% 17.6%
ICCtotal 0.055 mA (1 + 0.170 + 0.176 + 0.175)⋅ 0.084 mA≈≈
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