ATmega32U4 Atmel Corporation, ATmega32U4 Datasheet - Page 39

• Manufacturer Part Number: ATmega32U4
• Manufacturer: Atmel Corporation

Specifications of ATmega32U4

• Flash (kbytes): 32 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 14
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 26
• Ext Interrupts: 13
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 12
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 3.3
• 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: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 4
• Output Compare Channels: 12
• Input Capture Channels: 2
• Pwm Channels: 8
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

6.10
6.10.1
7766F–AVR–11/10
PLL
Internal PLL
the selected clock source has a higher frequency than the maximum frequency of the device at
the present operating conditions. The device is shipped with the CKDIV8 Fuse programmed.
Table 6-10.
The PLL is used to generate internal high frequency (up to 96MHz) clock for USB interface
and/or High Speed Timer module, the PLL input is supplied from an external low-frequency
clock (the crystal oscillator or external clock input pin from XTAL1).
The internal PLL in ATmega16U4/ATmega32U4 generates a clock frequency between 32MHz
and 96 MHz from nominally 8MHz input.
The source of the 8MHz PLL input clock is the output of the internal PLL clock prescaler that
generates the 8MHz from the clock source multiplexer output (See
face). The PLL prescaler allows a direct connection (8MHz oscillator) or a divide-by-2 stage for a
16MHz clock input.
The PLL output signal enters the PLL Postcaler stage before being distributed to the USB and
High Speed Timer modules. Each of these modules can choose an independent division ratio.
CLKPS3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Clock Prescaler Select
CLKPS2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
CLKPS1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
CLKPS0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Clock Division Factor
ATmega16/32U4
Section 6.10.2
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
128
256
16
32
64
1
2
4
8
for PLL inter-
39