ATMEGA644-20PU Atmel, ATMEGA644-20PU Datasheet - Page 34

• Manufacturer Part Number: ATMEGA644-20PU
• Description: IC AVR MCU FLASH 64K 40DIP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644-20PU

• 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): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-DIP (0.600", 15.24mm)
• Processor Series: ATMEGA64x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: 2-Wire/SPI/USART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 32
• Number Of Timers: 3
• Operating Supply Voltage: 2.7 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT, ATAVRRZ541, ATAVRRAVEN, ATAVRRZRAVEN, ATAVRRZUSBSTICK, ATAVRRZ201
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 8-ch x 10-bit
• Controller Family/series: AVR MEGA
• No. Of I/o's: 32
• Eeprom Memory Size: 2KB
• Ram Memory Size: 4KB
• Cpu Speed: 20MHz
• No. Of Timers: 3
• Rohs Compliant: Yes
• Package: 40PDIP
• Device Core: AVR
• Family Name: ATmega
• Maximum Speed: 20 MHz
• For Use With: ATSTK600-TQFP44 - STK600 SOCKET/ADAPTER 44-TQFPATSTK600-DIP40 - STK600 SOCKET/ADAPTER 40-PDIP770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAGATAVRISP2 - PROGRAMMER AVR IN SYSTEM
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

7.7
34
128 kHz Internal Oscillator
ATmega644
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 7-10.
Note:
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 7-11.
BOD enabled
Fast rising power
Slowly rising power
Power Conditions
7-11.
1. The frequency is preliminary value. Actual value is TBD.
128 kHz Internal Oscillator Operating Modes
Start-up Times for the 128 kHz Internal Oscillator
Nominal Frequency
128 kHz
Start-up Time from Power-
down and Power-save
Reserved
6 CK
6 CK
6 CK
Table
Additional Delay from
7-10.
14CK + 64 ms
14CK + 4 ms
Reset
14CK
CKSEL3..0
0011
2593N–AVR–07/10
SUT1..0
00
01
10
11