ATMEGA644P-20PQ Atmel, ATMEGA644P-20PQ Datasheet - Page 53

• Manufacturer Part Number: ATMEGA644P-20PQ
• Description: MCU AVR 64K FLASH 20MHZ 40-PDIP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644P-20PQ

• 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)
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.5
8.6
8011O–AVR–07/10
Brown-out Detection
Watchdog Reset
ATmega164P/324P/644P has an On-chip Brown-out Detection (BOD) circuit for monitoring the
V
can be selected by the BODLEVEL Fuses. The trigger level has a hysteresis to ensure spike
free Brown-out Detection. The hysteresis on the detection level should be interpreted as V
V
When the BOD is enabled, and V
8-5 on page
trigger level (V
out period t
The BOD circuit will only detect a drop in V
ger than t
Figure 8-5.
When the Watchdog times out, it will generate a short reset pulse of one CK cycle duration. On
the falling edge of this pulse, the delay timer starts counting the Time-out period t
page 61
Figure 8-6.
CC
BOT
level during operation by comparing it to a fixed trigger level. The trigger level for the BOD
+ V
for details on operation of the Watchdog Timer.
HYST
BOD
CC
TOUT
53), the Brown-out Reset is immediately activated. When V
/2 and V
given in
Brown-out Reset During Operation
Watchdog Reset During Operation
BOT+
INTERNAL
TIME-OUT
has expired.
RESET
RESET
in
V
CC
BOT-
Figure 8-5 on page
”System and Reset Characteristics” on page
= V
BOT
- V
CC
HYST
decreases to a value below the trigger level (V
V
CK
BOT-
/2.
53), the delay counter starts the MCU after the Time-
CC
if the voltage stays below the trigger level for lon-
ATmega164P/324P/644P
V
t
TOUT
BOT+
331.
CC
increases above the
TOUT
BOT-
. Refer to
in
Figure
BOT+
53
=