ATMEGA88P-20AUR Atmel, ATMEGA88P-20AUR Datasheet - Page 33

• Manufacturer Part Number: ATMEGA88P-20AUR
• Description: MCU AVR 8KB FLASH 20MHZ 32TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA88P-20AUR

• 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: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.5
8025L–AVR–7/10
Low Frequency Crystal Oscillator
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.
ATmega48P/88P/168P oscillator is optimized for very low power consumption, and thus when
selecting crystals, see
9.0 pF and 12.5 pF crystals
Table 8-7.
Note:
Table 8-8.
The Low-frequency Crystal Oscillator provides an internal load capacitance of typical 6 pF at
each TOSC pin. The external capacitance (C) needed at each TOSC pin can be calculated by
using:
where CL is the load capacitance for a 32.768 kHz crystal specified by the crystal vendor and C
is the total stray capacitance for one TOSC pin.
Crystals specifying load capacitance (CL) higher than 6 pF, require external capacitors applied
as described in
The Low-frequency Crystal Oscillator must be selected by setting the CKSEL Fuses to “0110” or
“0111”, as shown in
Table
Table 8-9.
ATmega48P/88P/169P
SUT[1:0]
00
01
10
11
8-9.
1. Maximum ESR is typical value based on characterization
Device
Maximum ESR Recommendation for 32.768 kHz Crystal
Capacitance for the Low-frequency Crystal Oscillator
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Additional Delay from Reset (V
Figure 8-2 on page
Crystal CL (pF)
Table
12.5
6.5
9.0
Table 8-7 on page 33
8-10. Start-up times are determined by the SUT Fuses as shown in
4 CK + 4.1 ms
4 CK + 65 ms
System Osc.
32 kHz Osc.
Timer Osc.
4 CK
Type
30.
C
=
CC
2 CL
for maximum ESR recommendations on 6.5 pF,
⋅
= 5.0V)
Reserved
–
C
(Xtal1/Tosc1)
ATmega48P/88P/168P
s
Recommended Usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
18 pF
18 pF
Cap
Max ESR [kΩ]
75
65
30
(Xtal2/Tosc2)
(1)
8 pF
8 pF
Cap
33
S