User Manual

324
ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]
8271E–AVR–07/2012
30.1.3 ATmega48A: 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 Reduc-
tion Register. See ”Power Reduction Register” on page 41 for details.
It is possible to calculate the typical current consumption based on the numbers from Table 30-2 on page 324 for
other V
CC
and frequency settings than listed in Table 30-1 on page 324.
30.1.3.1 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 30-4 on page 349, 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 30-53 on page 346, we find that the idle current
consumption is ~0.028 mA at V
CC
= 2.0V and F = 1MHz. The total current consumption in idle mode with TIMER1,
ADC, and SPI enabled, gives:
Table 30-1. ATmega48PA: 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 2.9uA 20.7uA 97.4uA
PRTWI 6.0uA 44.8uA 219.7uA
PRTIM2 5.0uA 34.5uA 141.3uA
PRTIM1 3.6uA 24.4uA 107.7uA
PRTIM0 1.4uA 9.5uA 38.4uA
PRSPI 5.0uA 38.0uA 190.4uA
PRADC 6.1uA 47.4uA 244.7uA
Table 30-2. ATmega48PA: Additional Current Consumption (percentage) in Active and Idle mode
PRR bit
Additional Current consumption
compared to Active with external
clock (see Figure 30-48 on page
344 and Figure 30-49 on page
344)
Additional Current consumption
compared to Idle with external
clock (see Figure 30-53 on page
346 and Figure 30-54 on page
347)
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%
ICCtotal 0.028 mA (1 + 0.112 + 0.221 + 0.176) 0.042 mA