ATmega644 Atmel Corporation, ATmega644 Datasheet - Page 34

• Manufacturer Part Number: ATmega644
• Manufacturer: Atmel Corporation

Specifications of ATmega644

• Flash (kbytes): 64 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 32
• Ext Interrupts: 32
• Usb Speed: No
• Usb Interface: No
• Spi: 3
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 4
• Eeprom (bytes): 2048
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 6
• Input Capture Channels: 1
• Pwm Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

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