Datasheet

538
ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET]
8284E–AVR–02/2013
31.7.3 Atmel ATmega649A: Supply current of I/O 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 ”PRR – Power Reduction Register” on page 45 for details.
It is possible to calculate the typical current consumption based on the numbers from Table 31-14 on page 538 for
other V
CC
and frequency settings than listed in Table 31-13 on page 538.
31.7.3.1 Example 1
Calculate the expected current consumption in idle mode with USART0, TIMER1, and SPI enabled at V
CC
= 3.0V
and F = 1MHz. From Table 31-14 on page 538, second column, we see that we need to add 49.8% for the
USART0, 48.6% for the SPI, and 46.3% for the TIMER1 module. Reading from Figure 31-371 on page 536, we find
that the idle current consumption is ~0.13mA at V
CC
= 3.0V and F = 1MHz. The total current consumption in idle
mode with USART0, TIMER1, and SPI enabled, gives:
Table 31-13. 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
PRADC 23.75µA 212.1µA 938µA
PRUSART0 36.7µA 210.4µA 939µA
PRSPI 32.1µA 213µA 940µA
PRTIM1 24.2µA 217µA 940µA
PRLCD 27.3µA 208.8µA 935µA
Table 31-14. Additional current consumption (percentage) in Active and Idle mode.
PRR bit
Additional current consumption
compared to Active with external clock
(see Figure 31-365 on page 533 and
Figure 31-366 on page 533)
Additional current consumption
compared to Idle with external clock
(see Figure 31-370 on page 535 and
Figure 31-371 on page 536)
PRADC 11.9% 45.7%
PRUSART0 13.2% 49.8%
PRSPI 12.8% 48.6%
PRTIM1 12.1% 46.3%
PRLCD 12.3% 46.7%
ICCtotal 0.13mA 1 0.498 0.486 0.463+++ 0.45mA