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
, 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
, 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
Additional Current consumption
compared to Idle with external clock
(see
)
PRTIM1
17.3%
68.4 %
PRTIM0
1.8 %
7.3 %
PRUSI
1.6 %
6.4 %
PRADC
5.4 %
21.4 %
I
CC
total
0,25
(
)
mA
1
0,064
0,073
0,214
+
+
+
(
)
•
0,337
mA
≈
≈