ATMEGA649A-AU Atmel, ATMEGA649A-AU Datasheet - Page 35

• 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

8.7
8284A–AVR–10/10
External Clock
The Low-frequency Crystal Oscillator provides an internal load capacitance,
each TOSC pin.
Table 8-9.
The capacitance (Ce + Ci) needed at each TOSC pin can be calculated by using:
where
Ce - is optional external capacitors as described in
Ci - is the pin capacitance in
CL - is the load capacitance for a 32.768 kHz crystal specified by the crystal vendor.
C
Crystals specifying load capacitance (CL) higher than the ones given in the
external capacitors applied as described in
To find suitable load capacitance for a 32.768 kHz crystal, please consult the crystal datasheet.
The Low-frequency Crystal Oscillator must be selected by setting the CKSEL Fuses to “0110” or
“0111” as shown in
shown in
Table 8-10.
Table 8-11.
Note:
To drive the device from an external clock source, XTAL1 should be driven as shown in
8-3. To run the device on an external clock, the CKSEL Fuses must be programmed to “0000”.
ATmega169A/169PA/329A/329PA/3290A
S
CKSEL3...
ATmega169A/169PA/329A/329PA/649A/649P/3290A/3290PA/6490A/6490P
SUT1..0
- is the total stray capacitance for one TOSC pin.
0110
/3290PA/649A/649P/6490A/6490P
0111
00
01
10
11
0
(1)
1. This option should only be used if frequency stability at start-up is not important for the
Table
application
Capacitance for Low-frequency Oscillator.
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Additional Delay from Reset (V
8-10.
Device
Table 8-11 on page
Power-down and Power-save
Start-up Time from
4 CK + 4.1 ms
4 CK + 65 ms
Table 8-10
32K CK
1K CK
4 CK
Ce
35. Start-up times are determined by the SUT Fuses as
+
32kHz Osc. Type
Ci
System Osc.
Figure 8-2 on page
Timer Osc.
CC
=
= 5.0V)
2 CL
⋅
Reserved
Figure 8-2 on page 33
–
C
s
Recommended Usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
Recommended Usage
Stable frequency at start-up
Cap(Xtal1/Tosc1)
33.
16 pF
16 pF
Table
Cap(Xtal2/Tosc2)
seeTable 8-9
8-9, require
6 pF
6 pF
Figure
35
at