ATMEGA644PA-AUR Atmel, ATMEGA644PA-AUR Datasheet - Page 33
![IC MCU AVR 64K FLASH 44TQFP](/photos/6/70/67042/313-44-tqfp_sml.jpg)
ATMEGA644PA-AUR
Manufacturer Part Number
ATMEGA644PA-AUR
Description
IC MCU AVR 64K FLASH 44TQFP
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA644PA-AUR
Core Processor
AVR
Core Size
8-Bit
Speed
20MHz
Connectivity
I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
32
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
44-TQFP, 44-VQFP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
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8.3
8272A–AVR–01/10
Low Power Crystal Oscillator
This Crystal Oscillator is a low power oscillator, with reduced voltage swing on the XTAL2 out-
put. It gives the lowest power consumption, but is not capable of driving other clock inputs, and
may be more susceptible to noise in noisy environments. In these cases, refer to the
Crystal Oscillator” on page
Some initial guidelines for choosing capacitors for use with crystals are given in
crystal should be connected as described in
The Low Power Oscillator can operate in three different modes, each optimized for a specific fre-
quency range. The operating mode is selected by the fuses CKSEL3..1 as shown in
Table 8-3.
Notes:
The CKSEL0 Fuse together with the SUT1..0 Fuses select the start-up times as shown in
8-4.
Table 8-4.
164A/164PA/324A/324PA/644A/644PA/1284/1284P
Oscillator Source /
Power Conditions
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Ceramic resonator, BOD
enabled
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Frequency Range (MHz)
1. If the crystal frequency exceeds the specification of the device (depends on V
2. This is the recommended CKSEL settings for the different frequency ranges.
3. This option should not be used with crystals, only with ceramic resonators.
Fuse can be programmed in order to divide the internal frequency by 8. It must be ensured
that the resulting divided clock meets the frequency specification of the device.
8.0 - 16.0
0.4 - 0.9
0.9 - 3.0
3.0 - 8.0
Low Power Crystal Oscillator Operating Modes
Start-up Times for the Low Power Crystal Oscillator Clock Selection
34.
Start-up Time from
Power-down and
Power-save
258 CK
258 CK
1K CK
1K CK
1K CK
CKSEL3..1
100
101
110
111
”Clock Source Connections” on page
(3)
(2)
Additional Delay
14CK + 4.1 ms
14CK + 4.1 ms
Recommended Range for Capacitors C1
14CK + 65 ms
14CK + 65 ms
(V
from Reset
CC
14CK
= 5.0V)
(1)
(2)
(1)
(2)
(1)
(2)
and C2 (pF)
12 - 22
12 - 22
12 - 22
–
CKSEL0
0
0
0
0
1
CC
Table
32.
), the CKDIV8
Table
”Full Swing
SUT1..0
8-3. The
00
01
10
11
00
Table
8-3.
33
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