ATMEGA329P-20MN Atmel, ATMEGA329P-20MN Datasheet - Page 31

• Manufacturer Part Number: ATMEGA329P-20MN
• Description: IC MCU AVR 32K 20MHZ 64QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA329P-20MN

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 54
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2K 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: 64-MLF®, 64-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.6
8021G–AVR–03/11
Calibrated Internal RC Oscillator
The capacitance (Ce + Ci) needed at each TOSC pin can be calculated by using:
where
Ce - is optional external capacitors as described in
Ci - is the pin capacitance in
CL - is the load capacitance for a 32.768kHz crystal specified by the crystal vendor.
C
Crystals specifying load capacitance (CL) higher than the ones given in the
30, require external capacitors applied as described in
To find suitable load capacitance for a 32.768kHz crystal, please consult the crystal datasheet.
The Low-frequency Crystal Oscillator must be selected by setting the CKSEL Fuses to “0110” or
“0111” as shown in
Table
Table 8-7.
Table 8-8.
Note:
By default, the Internal RC Oscillator provides an approximate 8MHz clock. Though voltage and
temperature dependent, this clock can be very accurately calibrated by the user. The device is
shipped with the CKDIV8 Fuse programmed. See
more details.
This clock may be selected as the system clock by programming the CKSEL Fuses as shown in
Table 8-9 on page
hardware loads the pre-programmed calibration value into the OSCCAL Register and thereby
automatically calibrates the RC Oscillator. The accuracy of this calibration is shown as Factory
calibration in
By changing the OSCCAL register from SW, see
page
The accuracy of this calibration is shown as User calibration in
S
CKSEL3...
SUT1..0
- is the total stray capacitance for one TOSC pin.
0110
0111
00
01
10
11
35, it is possible to get a higher calibration accuracy than by using the factory calibration.
0
8-7.
(1)
1. This option should only be used if frequency stability at start-up is not important for the
application
Table 28-4 on page
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Additional Delay from Reset (V
32. If selected, it will operate with no external components. During reset,
Power-down and Power-save
Table
Start-up Time from
8-8. Start-up times are determined by the SUT Fuses as shown in
4 CK + 4.1ms
4 CK + 65ms
Table 8-7 on page 31
32K CK
1K CK
4 CK
335.
Ce
+
Ci
CC
=
= 5.0V)
2 CL
”OSCCAL – Oscillator Calibration Register” on
⋅
Reserved
Figure 8-2 on page 29
”System Clock Prescaler” on page 33
–
Figure 8-2 on page
C
s
Recommended Usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
Recommended Usage
Stable frequency at start-up
ATmega329P/3290P
Table 28-4 on page
29.
Table 8-6 on page
335.
for
31