ATMEGA644A-AUR Atmel, ATMEGA644A-AUR Datasheet - Page 38
![IC MCU AVR 64K FLASH 44TQFP](/photos/6/70/67042/313-44-tqfp_sml.jpg)
ATMEGA644A-AUR
Manufacturer Part Number
ATMEGA644A-AUR
Description
IC MCU AVR 64K FLASH 44TQFP
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA644A-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
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Manufacturer
Quantity
Price
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8.7
8.8
8272A–AVR–01/10
128 kHz Internal Oscillator
External Clock
The 128 kHz internal Oscillator is a low power Oscillator providing a clock of 128 kHz. The fre-
quency is nominal at 3V and 25°C. This clock may be select as the system clock by
programming the CKSEL Fuses to “0011” as shown in
Table 8-12.
Note:
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 8-13.
To drive the device from an external clock source, XTAL1 should be driven as shown in
8-4. To run the device on an external clock, the CKSEL Fuses must be programmed to “0000”.
Figure 8-4.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
164A/164PA/324A/324PA/644A/644PA/1284/1284P
BOD enabled
Fast rising power
Slowly rising power
Power Conditions
8-13.
8-15.
1. Note that the 128kHz oscillator is a very low power clock source, and is not designed for high
accuracy.
128 kHz Internal Oscillator Operating Modes
Start-up Times for the 128 kHz Internal Oscillator
External Clock Drive Configuration
Nominal Frequency
EXTERNAL
128 kHz
SIGNAL
CLOCK
Start-up Time from Power-
down and Power-save
NC
Reserved
6 CK
6 CK
6 CK
XTAL2
XTAL1
GND
Table
(2)
Additional Delay from
8-12.
14CK + 64 ms
14CK + 4 ms
Reset
14CK
CKSEL3..0
0011
SUT1..0
00
01
10
11
Figure
38
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