406
8025I–AVR–02/09
ATmega48P/88P/168P/328P
27.4.3 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 27-8
on page 406 for other V
CC
and frequency settings than listed in Table 27-7 on page 406.
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 27-8 on page 406, third column, we see that we need
to add 14.5% for the TIMER1, 22.1% for the ADC, and 15.7% for the SPI module. Reading from
Figure 27-145 on page 404, 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 27-7. 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 3.20 µA 22.17 µA 100.25 µA
PRTWI 7.34 µA 46.55 µA 199.25 µA
PRTIM2 7.34 µA 50.79 µA 224.25 µA
PRTIM1 6.19 µA 41.25 µA 176.25 µA
PRTIM0 1.89 µA 14.28 µA 61.13 µA
PRSPI 6.94 µA 43.84 µA 186.50 µA
PRADC 8.66 µA 61.80 µA 295.38 µA
Table 27-8. Additional Current Consumption (percentage) in Active and Idle mode
PRR bit
Additional Current consumption
compared to Active with external
clock (see Figure 27-139 on page
401 and Figure 27-140 on page
401)
Additional Current consumption
compared to Idle with external
clock (see Figure 27-144 on page
403 and Figure 27-145 on page
404)
PRUSART0 1.4 % 7.8%
PRTWI 3.0 % 16.6 %
PRTIM2 3.3 % 17.8 %
PRTIM1 2.7 % 14.5 %
PRTIM0 0.9 % 4.8 %
PRSPI 2.9 % 15.7 %
PRADC 4.1 % 22.1 %
ICCtotal 0.045 mA (1 + 0.145 + 0.221 + 0.157)⋅ 0.069 mA≈≈
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