ATMEGA88-20MUR Atmel, ATMEGA88-20MUR Datasheet - Page 33

• Manufacturer Part Number: ATMEGA88-20MUR
• Description: MCU AVR 8K FLASH 20MHZ 32QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA88-20MUR

• 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: 23
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1K 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: *
• Cpu Family: ATmega
• Device Core: AVR
• Device Core Size: 8b
• Frequency (max): 20MHz
• Interface Type: SPI/TWI/USART
• Total Internal Ram Size: 1KB
• # I/os (max): 23
• Number Of Timers - General Purpose: 3
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 2.7V
• On-chip Adc: 8-chx10-bit
• Instruction Set Architecture: RISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 32
• Package Type: MLF EP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

9.5
9.6
2545T–AVR–05/11
Low frequency crystal oscillator
Calibrated internal RC oscillator
The device can utilize a 32.768kHz watch crystal as clock source by a dedicated low frequency
crystal oscillator. The crystal should be connected as shown in
oscillator is selected, start-up times are determined by the SUT fuses and CKSEL0 as shown in
Table
Table 9-7.
Note:
By default, the internal RC oscillator provides an approximate 8.0MHz 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 9-8 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
When this oscillator is used as the chip clock, the Watchdog Oscillator will still be used for the
watchdog timer and for the reset time-out. For more information on the pre-programmed calibra-
tion value, see the section
Power conditions
BOD enabled
Fast rising power
Slowly rising power
BOD enabled
Fast rising power
Slowly rising power
37, it is possible to get a higher calibration accuracy than by using the factory calibration.
9-7.
1. These options should only be used if frequency stability at start-up is not important for the
application.
Table 29-1 on page
Start-up times for the low frequency crystal oscillator clock selection.
34. If selected, it will operate with no external components. During reset,
“Calibration byte” on page
Start-up time from
power-down and
Reserved
Reserved
power-save
306.
32KCK
32KCK
32KCK
1KCK
1KCK
1KCK
“OSCCAL – Oscillator calibration register” on
288.
Additional delay
“System clock prescaler” on page 36
14CK + 4.1ms
14CK + 65ms
14CK + 4.1ms
14CK + 65ms
(V
from reset
CC
14CK
14CK
= 5.0V)
ATmega48/88/168
Figure 9-2 on page
Table 29-1 on page
(1)
(1)
(1)
CKSEL0
1
1
0
0
0
0
1
1
30. When this
306.
SUT1..0
00
01
10
11
00
01
10
11
for
33