ATMEGA644P-A15MZ Atmel, ATMEGA644P-A15MZ Datasheet - Page 37

• Manufacturer Part Number: ATMEGA644P-A15MZ
• Description: MCU AVR 64KB FLASH 16MHZ 44QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644P-A15MZ

• Package / Case: 44-VQFN Exposed Pad
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Speed: 16MHz
• Number Of I /o: 32
• Eeprom Size: 2K x 8
• Core Processor: AVR
• Program Memory Type: FLASH
• Ram Size: 4K x 8
• Program Memory Size: 64KB (64K x 8)
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Connectivity: I²C, SPI, UART/USART
• Core Size: 8-Bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

7.7
7.8
7674F–AVR–09/09
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 7-12.
Note:
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 7-13.
To drive the device from an external clock source, XTAL1 should be driven as shown in
7-4. To run the device on an external clock, the CKSEL Fuses must be programmed to “0000”.
Figure 7-4.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 7-14.
BOD enabled
Fast rising power
Slowly rising power
Power Conditions
7-13.
7-15.
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
External Clock Drive Configuration
Crystal Oscillator Clock Frequency
Nominal Frequency
Nominal Frequency
0 - 20 kHz
128 kHz
EXTERNAL
Power-down and Power-save
SIGNAL
CLOCK
NC
Start-up Time from
Reserved
6 CK
6 CK
6 CK
ATmega164P/324P/644P
XTAL2
XTAL1
GND
Table
7-12.
Additional Delay from
14CK + 64 ms
14CK + 4 ms
Reset
14CK
CKSEL3..0
CKSEL3..0
0011
0000
SUT1..0
01
10
00
11
Figure
37