WM8311GEB/V Wolfson Microelectronics, WM8311GEB/V Datasheet - Page 130

• Manufacturer Part Number: WM8311GEB/V
• Description: POWER MANAGEMENT SUBSYSTEM, 121BGA
• Manufacturer: Wolfson Microelectronics

Specifications of WM8311GEB/V

• Supply Voltage: 5.5V
• No. Of Step-down Dc - Dc Converters: 4
• No. Of Ldo Regulators: 7
• Digital Ic Case Style: BGA
• No. Of Pins: 121
• No. Of Regulated Outputs: 9
• Operating Temperature Range: -40°C To
• Rohs Compliant: Yes
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

WM8311
w
Touch pressure can only be determined indirectly, using the results of two separate measurements.
A constant current is applied through the plates, and the voltage on each plate is measured. The
difference between the two voltages is proportional to the resistance between the plates, which is a
measure of the pressure being applied to the panel.
The configuration is illustrated in Figure 31. In this example, a constant current flows from the Top
(Y
turn, and the difference, V
resistance between the plates. The smaller the measured resistance, the greater the pressure being
applied.
Figure 31 Z-axis (Pressure) Measurement on 4-wire Touch Panel
19.6.2 5-WIRE TOUCH PANEL OPERATION
In 5-wire operation, the Touch Panel interface connects to the four separate corners of one sheet
and to a single point on the other sheet. The illustrations show the top sheet for wiper contact and the
bottom sheet for corner contacts, but the reverse is also possible.
The principles of operation are the same for 5-wire and 4-wire modes, but different configuration of
the switching matrix within the Touch Panel controller is required in order to implement the equivalent
functionality.
X-axis measurement is performed by applying a potential difference between the Left and Right sides
of the touch panel. This requires the two Left corners to be connected to one potential and the two
Right corners connected to another. When contact is made between the two sheets, the voltage
present on the Wiper connection is a measure of the X-axis position of the contact. The configuration
is illustrated in Figure 32.
Figure 32 X-axis Measurement on 5-wire Touch Panel
Y-axis measurement is performed by applying a potential difference between the Top and Bottom
sides of the touch panel. This requires the two Top corners to be connected to one potential and the
two Bottom corners connected to another. When contact is made between the two sheets, the
voltage present on the Wiper connection is a measure of the Y-axis position of the contact. The
configuration is illustrated in Figure 33.
+
) connection to the Left (X
X
- V
-
) connection. The Right (X
Y
is equal to I
Y
X
Y
X
+
+
-
-
(GPIO14)
(GPIO13)
(GPIO16)
(GPIO15)
P
x R
C
, where I
+
) and Bottom (Y
WM8311
ADC
AUX
P
is the current applied and R
TPVDD
TPGND
Pressure
PP, December 2009, Rev 3.0
-
) points are measured in
Pre-Production
C
is the
130