WM8311GEB/V Wolfson Microelectronics, WM8311GEB/V Datasheet - Page 124

• 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
19 TOUCH PANEL CONTROLLER
19.1 GENERAL DESCRIPTION
19.2 TOUCH PANEL CONFIGURATION
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The WM8311 incorporates a Touch Panel controller interface, supporting standard resistive 4-wire
and 5-wire panel types. The controller supports X, Y co-ordinate measurement and Pen Down
detection. The 4-wire configuration also supports Touch Pressure (Z-axis) measurement.
The Touch Panel interfaces via GPIO pins 13-16. (In 5-wire mode, the AUXADCIN4 pin is also used.)
The controller provides high resolution digitiser measurements, using the same 12-bit AUXADC as
described in Section 18. Touch Panel conversion requests are interleaved with AUXADC
measurement requests.
The Touch Panel can be enabled or disabled in the SLEEP state; Pen Down detection can be used
to issue a WAKE request, including when the Touch Panel is disabled.
Touch Panel Interrupts can be generated on completion of a set of measurements, or on Pen Down
detection. Read access to the Touch Panel measurement data is controlled in order to ensure the
host always reads a complete set of data, and does not read mixed data that relates to separate
measurement events.
An overview of Touch Panel operating principles is provided in Section 19.6.
The Touch Panel interface uses GPIO pins 13-16. When the Touch Panel is enabled, the GPIO
functionality on these pins must be disabled by tri-stating the GPIO using GPn_TRI (see
Section 21.3).
When the Touch Panel is enabled, then TPVDD should be connected to the LDO13VOUT (INTVDD)
power domain. It is important that TPVDD is not connected to a higher voltage than this. Note that,
due to the ratiometric measurement method, the accuracy of the supply voltage does not affect the
measurement accuracy.
The 5-wire Touch Panel interface also uses the AUXADCIN4 pin; in this case, the AUXADCIN4 input
is not available to the AUXADC function.
The Touch Panel pin configuration differs between 4-wire and 5-wire modes as follows:
Table 70 Touch Panel Pin Configuration
The Touch Panel 4-wire or 5-wire mode is selected using the TCH_5WIRE bit.
Pressure measurement (4-wire mode only) uses a constant current source to measure the resistance
between the top and bottom sheets of the touch panel. The current is selectable using TCH_ISEL, to
suit different types of touch panel.
Pen Down detection sensitivity can be controlled using TCH_RPU. Decreasing the resistance makes
the touch panel less sensitive; increasing the resistance makes the touch panel more sensitive.
The Touch Panel configuration register bits are defined in Table 71.
AUXADCIN4
PIN NAME
GPIO13
GPIO14
GPIO15
GPIO16
4-WIRE FUNCTION
Bottom contact
Right contact
Top contact
Left contact
n/a
Bottom Right contact
5-WIRE FUNCTION
Bottom Left contact
Top Right contact
Top Left contact
Wiper Contact
PP, December 2009, Rev 3.0
Pre-Production
124