160
7598H–AVR–07/09
ATtiny25/45/85
23.2.1 Using the Power Reduction Register
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 33 for
details.
It is possible to calculate the typical current consumption based on the numbers from Table 2 for
other V
CC
and frequency settings than listed in Table 1.
23.2.1.1 Example 1
Calculate the expected current consumption in idle mode with USI, TIMER0, and ADC enabled
at V
CC
= 2.0V and F = 1MHz. From Table 23-2, third column, we see that we need to add 6.4%
for the USI, 7.3% for the TIMER0 module, and 21.4% for the ADC module. Reading from Figure
23-9, we find that the idle current consumption is ~0,25mA at V
CC
= 3.0V and F = 1MHz. The
total current consumption in idle mode with USI, TIMER0, and ADC enabled, gives:
Table 23-1. 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
PRTIM1 43 uA 270 uA 1090 uA
PRTIM0 5.0 uA 28 uA 116 uA
PRUSI 4.0 uA 25 uA 102 uA
PRADC 13 uA 84 uA 351 uA
Table 23-2.
Additional Current Consumption (percentage) in Active and Idle mode
PRR bit
Additional Current consumption
compared to Active with external
clock
(see Figure 23-1 and Figure 23-2)
Additional Current consumption
compared to Idle with external clock
(see Figure 23-6 and Figure 23-7)
PRTIM1 17.3% 68.4 %
PRTIM0 1.8 % 7.3 %
PRUSI 1.6 % 6.4 %
PRADC 5.4 % 21.4 %
ICCtotal 0,25()mA 1 0,064 0,073 0,214+++()• 0,337mA≈≈
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