ATAVRQTOUCHX Atmel, ATAVRQTOUCHX Datasheet - Page 112

• Manufacturer Part Number: ATAVRQTOUCHX
• Description: BOARD EVAL CAPACITIVE TOUCH
• Manufacturer: Atmel
• Series: QTouch™r

Specifications of ATAVRQTOUCHX

• Sensor Type: Touch, Capacitive
• Sensing Range: 1 Slider, 1 Wheel, 2 Buttons
• Interface: USB
• Voltage - Supply: 5V, USB
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: AT90USB1287, ATxmega128A1
• Silicon Manufacturer: Atmel
• Silicon Family Name: ATxmega
• Kit Contents: Board
• Svhc: No SVHC (15-Dec-2010)
• Core Architecture: AVR
• Core Sub-architecture: AVR19
• Kit Features: One Slider, One Wheel And 2
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Sensitivity: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

6.3.7.2.2
When the External Discharge arrangement is used, a logic-level (DIS) pin is connected to an
external resistor (Rdis) that can be used to control the discharge of the Capacitors. A typical
value for Rdis is 100 kOhm. This value of Rdis will give a discharge current of approximately
1.1V/(100 kOhm) = 11 microAmp. The case C shows this arrangement. The Resistive drive
option on the X and Yk lines can be optionally enabled or disabled with this arrangement. When
the Resistive drive is option is not enabled, it is recommended to use 1kOhm resistors on X and
Yk Lines external to the UC3L device.
6.3.7.2.3
When the SMP Discharge mode arrangement is used, a logic-level (SMP) pin is connected to the
capacitors through external high value resistors for the discharge of the capacitors. The case D
shows this arrangement. The Resistive drive option on the X and Yk lines can be optionally
enabled or disabled with this arrangement. When the Resistive drive is option is not enabled, it is
recommended to use 1kOhm resistors on X and Yk Lines external to the UC3L device.
6.3.7.2.4
The VDIV pin provides an option to make ACREFN a small positive voltage if required. The VDIV
pin is driven when the analog comparators are in use, and this signal can be used along with a
voltage divider arrangement to create a small positive offset on the ACREFN pin. The VDIVEN
option can be used optionally with any of the QMatrix modes discussed in the previous sections.
Typical values for Ra and Rb are Ra=16500 ohm and Rb = 50 ohm. Assuming a 3.3V I/O supply,
this will shift the comparator threshold by 3.3V*(Rb/(Ra+Rb)) which is 10 mV. The VDIVEN pin
option usage in the Internal Discharge mode scenario is shown in case E.
6.3.7.2.5
In order to prevent interference from the 50 or 60 Hz mains line the CAT can optionally trigger
QMatrix acquisition on the external SYNC input signal. The SYNC signal should be derived from
the mains line and the acquisition will trigger on a falling edge of this signal. The SYNC pin
option can be used with any of the QMatrix modes discussed in the previous sections. The
SYNC pin usage in the Internal Discharge mode scenario is shown in case F.
For QMatrix method SMP, DIS, VDIV and SYNC pin options discussed in this Section, Refer to
Section
112
6.3.15.2.13.
SMP Discharge Mode
VDIVEN Voltage Divider Enable option
External Discharge mode
SYNC pin option
8207J-AT42-02/11