ATmega48P Atmel Corporation, ATmega48P Datasheet - Page 33

• Manufacturer Part Number: ATmega48P
• Manufacturer: Atmel Corporation

Specifications of ATmega48P

• 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
8025M–AVR–6/11
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 9-7.
Note:
Table 9-8.
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 9-9.
ATmega48P/88P/169P
SUT[1:0]
00
01
10
11
9-9.
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 9-2 on page
Crystal CL (pF)
Table
12.5
6.5
9.0
Table 9-7 on page 33
9-10. 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