ATUC128L4U Atmel Corporation, ATUC128L4U Datasheet - Page 780

• Manufacturer Part Number: ATUC128L4U
• Manufacturer: Atmel Corporation

Specifications of ATUC128L4U

• Flash (kbytes): 128 Kbytes
• Pin Count: 48
• Max. Operating Frequency: 50 MHz
• Cpu: 32-bit AVR
• # Of Touch Channels: 17
• Hardware Qtouch Acquisition: Yes
• Max I/o Pins: 36
• Ext Interrupts: 36
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 1
• Twi (i2c): 2
• Uart: 4
• Lin: 4
• Ssc: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 12
• Adc Speed (ksps): 460
• Analog Comparators: 8
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 16
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: Yes
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.62 to 3.6
• Operating Voltage (vcc): 1.62 to 3.6
• Fpu: No
• Mpu / Mmu: Yes / No
• Timers: 6
• Output Compare Channels: 18
• Input Capture Channels: 12
• Pwm Channels: 35
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

ATUC64/128/256L3/4U
Problems with QMatrix acquisition of small sense capacitor voltages can be solved by connect-
ing the negative reference pin (ACREFN) to a voltage divider that produces a small positive
voltage (20 mV, typically) to cancel any negative input offset voltage. With a 3.3V supply, recom-
mended values for the voltage divider are Ra (resistor from positive supply to ACREFN) of 8200
ohm and Rb (resistor from ACREFN to ground) of 50 ohm. These recommended values will pro-
duce 20 mV on the ACREFN pin, which should generally be enough to compensate for the
worst-case negative input offset of the analog comparators.
Unfortunately, such a voltage divider constantly draws a small current from the power supply,
reducing battery life in portable applications. In order to prevent this constant power drain, the
CAT module provides a voltage divider enable pin (VDIVEN) that can be used for driving the
voltage divider. The VDIVEN pin provides power to the voltage divider only when the compara-
tors are actually performing QMatrix comparisons. When the comparators are inactive, the
VDIVEN output is zero. This minimizes the power consumed by the voltage divider.
780
32142A–12/2011