Datasheet

331
8018P–AVR–08/10
ATmega169P
28.3 Speed Grades
Maximum frequency is depending on V
CC.
As shown in Figure 28-1 and Figure 28-2 on page
332, the Maximum Frequency vs. V
CC
curve is linear between 1.8V < V
CC
< 4.5V. To calculate
the maximum frequency at a given voltage in this interval, use this equation:
To calculate required voltage for a given frequency, use this equation::
At 3 Volt, this gives:
Thus, when V
CC
= 3V, maximum frequency will be 9.33 MHz.
At 6 MHz this gives:
Thus, a maximum frequency of 6 MHz requires V
CC
= 2.25V.
Figure 28-1. Maximum Frequency vs. V
CC
, ATmega169PV
Table 28-1. Constants used to calculate maximum speed vs. V
CC
Voltage and Frequency range a b Vx Fy
2.7 < V
CC
< 4.5 or 8 < Frq < 16
8/1.8 1.8/8
2.7 8
1.8 < V
CC
< 2.7 or 4 < Frq < 8 1.8 4
Frequency a V Vx–()• Fy+=
Voltage b F Fy–()• Vx+=
Frequency
8
1.8
--------
32.7–()• 8+ 9.33==
Voltage
1.8
8
--------
64–()• 1.8+ 2.25==
8 MHz
4 MHz
1.8V 2.7V 5.5V
Safe Operating Area