ATMEGA1284P-MUR Atmel, ATMEGA1284P-MUR Datasheet - Page 35

• Manufacturer Part Number: ATMEGA1284P-MUR
• Description: MCU AVR 128KB FLASH 20MHZ 44VQFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA1284P-MUR

• 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: 128KB (64K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 4K x 8
• Ram Size: 16K 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-VQFN Exposed Pad
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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