ATmega3250 Atmel Corporation, ATmega3250 Datasheet - Page 31

• Manufacturer Part Number: ATmega3250
• Manufacturer: Atmel Corporation

Specifications of ATmega3250

• Flash (kbytes): 32 Kbytes
• Pin Count: 100
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 69
• Ext Interrupts: 25
• 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: No
• Crypto Engine: No
• Sram (kbytes): 2
• Eeprom (bytes): 1024
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• 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: 4
• Input Capture Channels: 1
• Pwm Channels: 4
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

9.7
9.8
2570N–AVR–05/11
Clock Output Buffer
Timer/Counter Oscillator
Figure 9-3.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table 9-10 on page
Table 9-10.
When applying an external clock, it is required to avoid sudden changes in the applied clock fre-
quency to ensure stable operation of the MCU. A variation in frequency of more than 2% from
one clock cycle to the next can lead to unpredictable behavior. It is required to ensure that the
MCU is kept in Reset during such changes in the clock frequency.
Note that the System Clock Prescaler can be used to implement run-time changes of the internal
clock frequency while still ensuring stable operation. Refer to
32
When the CKOUT Fuse is programmed, the system Clock will be output on CLKO. This mode is
suitable when the chip clock is used to drive other circuits on the system. The clock will be out-
put also during reset and the normal operation of I/O pin will be overridden when the fuse is
programmed. Any clock source, including internal RC Oscillator, can be selected when CLKO
serves as clock output. If the System Clock Prescaler is used, it is the divided system clock that
is output when the CKOUT Fuse is programmed.
Atmel ATmega325/3250/645/6450 share the Timer/Counter Oscillator Pins (TOSC1 and
TOSC2) with XTAL1 and XTAL2. This means that the Timer/Counter Oscillator can only be used
when the calibrated internal RC Oscillator is selected as system clock source. The Oscillator is
optimized for use with a 32.768kHz watch crystal. See
connection.
SUT1..0
for details.
00
01
10
11
Start-up Time from Power-
down and Power-save
External Clock Drive Configuration
Start-up Times for the External Clock Selection
31.
6 CK
6 CK
6 CK
EXTERNAL
SIGNAL
CLOCK
NC
Additional Delay from
Reset (V
Reserved
ATmega325/3250/645/6450
14CK + 4.1ms
14CK + 65ms
14CK
CC
= 5.0V)
XTAL2
XTAL1
GND
Figure 9-2 on page 28
“System Clock Prescaler” on page
BOD enabled
Fast rising power
Recommended Usage
Slowly rising power
for crystal
31