29. Typical Characteristics
The following charts show typical behavior. These figures are not tested during manufacturing.
All current consumption measurements are performed with all I/O pins configured as inputs and
with internal pull-ups enabled. A square wave generator with rail-to-rail output is used as clock
source.
All Active- and Idle current consumption measurements are done with all bits in the PRR register
set and thus, the corresponding I/O modules are turned off. Also the Analog Comparator is dis-
abled during these measurements. Table 29-1 on page 322 and Table 29-2 on page 323 show
the additional current consumption compared to ICC Active and ICC Idle for every I/O module con-
trolled by the Power Reduction Register. See “Power Reduction Register” on page 42 for details.
The power consumption in Power-down mode is independent of clock selection.
The current consumption is a function of several factors such as: operating voltage, operating
frequency, loading of I/O pins, switching rate of I/O pins, code executed and ambient tempera-
ture. The dominating factors are operating voltage and frequency.
The current drawn from capacitive loaded pins may be estimated (for one pin) as CL*VCC*f where
CL = load capacitance, VCC = operating voltage and f = average switching frequency of I/O pin.
The parts are characterized at frequencies higher than test limits. Parts are not guaranteed to
function properly at frequencies higher than the ordering code indicates.
The difference between current consumption in Power-down mode with Watchdog Timer
enabled and Power-down mode with Watchdog Timer disabled represents the differential cur-
rent drawn by the Watchdog Timer.
29.1 Active Supply Current
Figure 29-1. Active Supply Current vs. Frequency (0.1 - 1.0 MHz)
ACTIVE SUPPLY CURRENT vs. FREQUENCY
0.1 - 1.0 MHz
1.2
1
5.5 V
5.0 V
4.5 V
4.0 V
0.8
0.6
0.4
0.2
0
3.3 V
2.7 V
1.8 V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Frequency (MHz)
316
ATmega48/88/168
2545M–AVR–09/07
ATMEL [ ATMEL ]
