User Manual

424
ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]
8271E–AVR–07/2012
30.5.3 ATmega168A 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 30-12 on page 449 for
other V
CC
and frequency settings than listed in Table 30-11 on page 449.
30.5.3.1 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 30-12 on page 449, third column, we see that we need to add 10.3% for the TIMER1,
20.3% for the ADC, and 17.1% for the SPI module. Reading from Figure 30-241 on page 446, we find that the idle
current consumption is ~0.027 mA at V
CC
= 2.0V and F = 1MHz. The total current consumption in idle mode with
TIMER1, ADC, and SPI enabled, gives:
Table 30-9. ATmega168A: 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 2.86uA 20.3uA 52.2uA
PRTWI 6.00uA 44.1uA 122.0uA
PRTIM2 4.97uA 33.2uA 79.8uA
PRTIM1 3.50uA 23.0uA 55.3uA
PRTIM0 1.43uA 9.2uA 21.4uA
PRSPI 5.01uA 38.6uA 111.4uA
PRADC 6.34uA 45.7uA 123.6uA
Table 30-10. ATmega168A: Additional Current Consumption (percentage) in Active and Idle mode
PRR bit
Additional Current consumption
compared to Active with external
clock (see Figure 30-236 on page
443 and Figure 30-237 on page
444)
Additional Current consumption
compared to Idle with external
clock (see Figure 30-241 on page
446 and Figure 30-242 on page
446)
PRUSART0 1.5% 8.9%
PRTWI 3.2% 19.5%
PRTIM2 2.4% 14.8%
PRTIM1 1.7% 10.3%
PRTIM0 0.7% 4.1%
PRSPI 2.9% 17.1%
PRADC 3.4% 20.3%
ICCtotal 0.027 mA (1 + 0.103 + 0.203 + 0.171) 0.040 mA