ATMEGA649A-AU Atmel, ATMEGA649A-AU Datasheet - Page 36

• Manufacturer Part Number: ATMEGA649A-AU
• Description: IC MCU AVR 64K FLASH 64TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA649A-AU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 54
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-TQFP
• Processor Series: ATmega
• Core: AVR
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: SPI, USART
• Maximum Clock Frequency: 16 MHz
• Number Of Programmable I/os: 54
• Number Of Timers: 3
• Operating Supply Voltage: 3.3 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Operating Temperature Range: - 40 C to + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.8
8284A–AVR–10/10
Clock Output Buffer
Figure 8-3.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 8-12.
Table 8-13.
When applying an external clock, it is required to avoid sudden changes in the applied clock fre-
quency to ensure stable operation of the MCU. A variation in frequency of more than 2% from
one clock cycle to the next can lead to unpredictable behavior. It is required to ensure that the
MCU is kept in Reset during such changes in the clock frequency.
Note that the System Clock Prescaler can be used to implement run-time changes of the internal
clock frequency while still ensuring stable operation. Refer to
37
When the CKOUT Fuse is programmed, the system Clock will be output on CLKO. This mode is
suitable when the chip clock is used to drive other circuits on the system. The clock will be out-
put also during reset and the normal operation of I/O pin will be overridden when the fuse is
programmed. Any clock source, including internal RC Oscillator, can be selected when CLKO
serves as clock output. If the System Clock Prescaler is used, it is the divided system clock that
is output when the CKOUT Fuse is programmed.
ATmega169A/169PA/649A/649P
ATmega329A/329PA/3290A/3290PA/6490A/6490P
SUT1..0
ATmega169A/169PA/329A/329PA/649A/649P/3290A/3290PA/6490A/6490P
for details.
00
01
10
11
8-13.
Start-up Time from Power-
External Clock Drive Configuration
Crystal Oscillator Clock Frequency
Start-up Times for the External Clock Selection
down and Power-save
6 CK
6 CK
6 CK
EXTERNAL
SIGNAL
CLOCK
NC
Additional Delay from
Reset (V
Reserved
14CK + 4.1 ms
14CK + 65 ms
CKSEL3:0
0000
0000
XTAL2
XTAL1
GND
14CK
CC
= 5.0V)
”System Clock Prescaler” on page
Frequency Range
0 - 16 MHz
0 - 20 MHZ
BOD enabled
Fast rising power
Slowly rising power
Recommended Usage
36