ATmega48PA Atmel Corporation, ATmega48PA Datasheet - Page 33

• Manufacturer Part Number: ATmega48PA
• Manufacturer: Atmel Corporation

Specifications of ATmega48PA

• Flash (kbytes): 4 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 23
• Ext Interrupts: 24
• Usb Speed: No
• Usb Interface: No
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 0.5
• Eeprom (bytes): 256
• Self Program Memory: NO
• Dram Memory: No
• Nand Interface: No
• Picopower: Yes
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 6
• Input Capture Channels: 1
• Pwm Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

9.5
8271D–AVR–05/11
Low Frequency Crystal Oscillator
The Low-frequency Crystal Oscillator is optimized for use with a 32.768kHz watch crystal. When
selecting crystals, load capacitance and crystal’s Equivalent Series Resistance, ESR must be
t a k e n i n t o c o n s i d e r a t i o n . B o t h v a l u e s a r e s p e c i f i e d b y t h e c r y s t a l v e n d o r .
ATmega48A/PA/88A/PA/168A/PA/328/P oscillator is optimized for very low power consumption,
and thus when selecting crystals, see
9.0pF and 12.5pF crystals
Table 9-7.
Note:
The Low-frequency Crystal Oscillator provides an internal load capacitance, see
each TOSC pin.
Table 9-8.
The capacitance (Ce+Ci) needed at each TOSC pin can be calculated by using:
where:
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
shown in
Table 9-9.
C
ATmega48A/PA/88A/PA/168A/PA/3
=
SUT1...0
– 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
– CS - is the total stray capacitance for one TOSC pin.
2 CL
00
01
10
11
⋅
1. Maximum ESR is typical value based on characterization
Table
–
C
s
Device
Maximum ESR Recommendation for 32.768kHz Crystal
Capacitance for Low-frequency Oscillator
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
28/P
Additional Delay from Reset (V
Figure 9-2 on page
9-9.
Crystal CL (pF)
Table 9-10 on page
ATmega48A/PA/88A/PA/168A/PA/328/P
12.5
6.5
9.0
4 CK + 4.1ms
4 CK + 65ms
4 CK
Table 9-8
30.
32kHz Osc. Type
System Osc.
Table
Timer Osc.
34. Start-up times are determined by the SUT Fuses as
CC
for maximum ESR recommendations on 6.5pF,
= 5.0V)
Reserved
Recommended Usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
Cap(Xtal1/Tosc1)
Figure 9-2 on page 30
18pF
18pF
Max ESR [kΩ]
75
65
30
Cap(Xtal2/Tosc2)
(1)
Table 9-8
8pF
8pF
33
at