ATMEGA169P_1 Datasheet, PDF (329/393 Pages) ATMEL Corporation – 8-bit Microcontroller with 16K Bytes In-System Programmable Flash

ATmega169P
28.3 Speed Grades
Maximum frequency is depending on V_CC. As shown in Figure 28-1 and Figure 28-2, the Maxi-
mum 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:
Frequency = a • (V – Vx) + Fy
To calculate required voltage for a given frequency, use this equation::
Voltage = b • (F – Fy) + Vx
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
1.8 < V_CC < 2.7 or 4 < Frq < 8
2.7
8
8/1.8
1.8/8
1.8
4
At 3 Volt, this gives:Frequency
=
---⁸----
1.8
•
(
3
–
2.7 )
+
8
=
9.33
Thus, when V_CC = 3V, maximum frequency will be 9.33 MHz.
At 6 MHz this gives: Voltage
=
1_----._-8_--
8
•
(6
–
4
)
+
1.8
=
2.25
Thus, a maximum frequency of 6 MHz requires V_CC = 2.25V.
Figure 28-1. Maximum Frequency vs. V_CC, ATmega169PV
8 MHz
4 MHz
1.8V
Safe Operating Area
2.7V
5.5V
8018N–AVR–08/09
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