WM9712LGEFLSLASHV datasheet(38/77 Pages) WOLFSON

38 / 77 page

WM9712L

Production Data

PD Rev 4.5 August 2006

TOUCHPANEL INTERFACE

The WM9712L includes a touchpanel driver and digitiser circuit for use with 4-wire or 5-wire resistive

touchpanels. The following functions are implemented:

•

X co-ordinate measurement

•

Y co-ordinate measurement

•

Pen down detection, with programmable sensitivity

•

Touch pressure measurement (4-wire touchpanel only)

•

Auxiliary measurement from COMP1/AUX1 (pin 29), COMP2/AUX2 (pin 30),

BMON/AUX3 (pin 31), or WIPER/AUX4 (pin 12)

The touchpanel digitiser uses a very low power, 12-bit successive approximation type ADC. The

same ADC can also be used for battery and auxiliary measurements (see the “Battery Alarm and

Battery Measurement” and “Auxiliary ADC Inputs” sections).

An on-chip switch matrix connects each touchpanel terminal to the supply voltage TPVDD, to ground

(TPGND), or to the ADC input, as required.

SAR

ADC

zero power

comparator

PEN

DOWN

20K

10K

Figure 5 Touchpanel Switch Matrix

PRINCIPLE OF OPERATION - FOUR-WIRE TOUCHPANEL

Four-wire touchpanels are connected to the WM9712L as follows:

•

Right side contact = X+ (pin 14)

•

Left side contact = X- (pin 16)

•

Top side contact = Y+ (pin 15)

•

Bottom side contact = Y- (pin 17)

WM9712LGEFL/V 데이터시트(PDF) 38 Page - Wolfson Microelectronics plc