AT32UC3L-EK Atmel, AT32UC3L-EK Datasheet - Page 668

• Manufacturer Part Number: AT32UC3L-EK
• Description: KIT EVAL AVR32 UC3 MCU
• Manufacturer: Atmel
• Type: MCUr

Specifications of AT32UC3L-EK

• Contents: *
• Silicon Manufacturer: Atmel
• Core Architecture: AVR
• Core Sub-architecture: UC3L
• Kit Contents: Board
• Features: USB / Battery Powered, Board Controller / Bootloader
• Svhc: No SVHC (15-Dec-2010)
• Rohs Compliant: Yes
• Tool Type: Starter Kit
• Cpu Core: AVR 8
• Data Bus Width: 8 bit
• Processor Series: AT32
• Processor To Be Evaluated: AT32UC3L064
• Interface Type: USB, Capacitive Touch
• For Use With/related Products: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AT32UC3L016/32/64
Problems with QMatrix acquisition of small sense capapcitor 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 comparisions. When the comparators are inactive, the
VDIVEN output is zero. This minimizes the power consumed by the voltage divider.
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