ATMEGA644PA-AUR Atmel, ATMEGA644PA-AUR Datasheet - Page 35
ATMEGA644PA-AUR
Manufacturer Part Number
ATMEGA644PA-AUR
Description
IC MCU AVR 64K FLASH 44TQFP
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA644PA-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
Available stocks
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Quantity:
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8.5
8272A–AVR–01/10
Low Frequency Crystal Oscillator
Table 8-6.
Notes:
The Low-frequency Crystal Oscillator is optimized for use with a 32.768 kHz watch crystal.
When selecting crystals, load capasitance and crystal’s Equivalent Series Resistance, ESR
must be taken into consideration. Both values are specified by the crystal vendor.
ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P oscillator is optimized for very low
power consumption, and thus when selecting crystals, see
ESR recommendations on 9 pF and 12.5 pF crystals.
Table 8-7.
Note:
The Low-frequency Crystal Oscillator provides an internal load capacitance, see
35
Table 8-8.
The capacitance (Ce + Ci) needed at each TOSC pin can be calculated by using:
where:
164A/164PA/324A/324PA/644A/644PA/1284/1284P
Oscillator Source /
Power Conditions
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Crystal Oscillator, BOD
enabled
Crystal Oscillator, fast
rising power
Crystal Oscillator, slowly
rising power
ATmega164A/164PA/324A/324PA/
at each TOSC pin.
644A/644PA/1284/1284P
1. These options should only be used when not operating close to the maximum frequency of the
2. These options are intended for use with ceramic resonators and will ensure frequency stability
1. Maximum ESR is typical value based on characterization
device, and only if frequency stability at start-up is not important for the application. These
options are not suitable for crystals.
at start-up. They can also be used with crystals when not operating close to the maximum fre-
quency of the device, and if frequency stability at start-up is not important for the application.
Device
Start-up Times for the Full Swing Crystal Oscillator Clock Selection
Maximum ESR Recommendation for 32.768 kHz Watch Crystal
Capacitance for Low-frequency Oscillator
Crystal CL (pF)
12.5
9.0
Start-up Time from
Power-down and
Power-save
16K CK
16K CK
16K CK
32kHz Osc. Type
1K CK
1K CK
System Osc.
Ce
Timer Osc.
+
Ci
=
2 CL
⋅
Additional Delay
–
14CK + 4.1 ms
14CK + 65 ms
14CK + 4.1 ms
14CK + 65 ms
C
(V
Cap (Xtal1/Tosc1)
from Reset
s
CC
14CK
Table 8-7 on page 35
= 5.0V)
18 pF
6 pF
Max ESR [kΩ]
(2)
(2)
65
30
CKSEL0
Cap (Xtal2/Tosc2)
(1)
0
1
1
1
1
Table on page
for maximum
8 pF
6 pF
SUT1..0
11
00
01
10
11
35
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