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
for other V
CC
and frequency settings than listed in
Example
Calculate the expected current consumption in idle mode with TIMER1, ADC, and SPI enabled
at V
CC
= 2.0V and F = 1MHz. From
, 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
, 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
and
)
Additional Current consumption
compared to Idle with external
clock (see
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 %
I
CC
total
0.045 mA (1 + 0.145 + 0.221 + 0.157)
⋅
0.069 mA
≈
≈