Datasheet

291
ATmega48PA/88PA/168PA [DATASHEET]
9223F–AVR–04/14
30.2.3 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
Section 10.9 “Power Reduction Register” on page 37 for details.
It is possible to calculate the typical current consumption based on the numbers from Table 30-2 on page 281 for other V
CC
and frequency settings than listed in Table 30-1 on page 281.
30.2.3.1 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 30-2 on page 281, third column, we see that we need to add 11.2% for the TIMER1, 22.1% for the ADC, and
17.6% for the SPI module. Reading from Figure 30-3 on page 280, we find that the idle current consumption is ~0.028mA at
V
CC
= 2.0V and F = 1MHz. The total current consumption in idle mode with TIMER1, ADC, and SPI enabled, gives:
I
CCtotal
≈ 0.028mA (1 + 0.112 + 0221 + 0.176) ≈ 0.042mA
Table 30-3. 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 2.9µA 20.7µA 97.4µA
PRTWI 6.0µA 44.8µA 219.7µA
PRTIM2 5.0µA 34.5µA 141.3µA
PRTIM1 3.6µA 24.4µA 107.7µA
PRTIM0 1.4µA 9.5µA 38.4µA
PRSPI 5.0µA 38.0µA 190.4µA
PRADC 6.1µA 47.4µA 244.7µA
Table 30-4. Additional Current Consumption (Percentage) in Active and Idle Mode
PRR bit
Additional Current Consumption Compared
to Active with External Clock (see Figure 30-1
on page 279 and Figure 30-2 on page 279)
Additional Current Consumption Compared
to Idle with External Clock (see Figure 30-3
on page 280 and Figure 30-4 on page 280)
PRUSART0 1.8% 11.4%
PRTWI 3.9% 20.6%
PRTIM2 2.9% 15.7%
PRTIM1 2.1% 11.2%
PRTIM0 0.8% 4.2%
PRSPI 3.3% 17.6%
PRADC 4.2% 22.1%