WM9713 datasheet(59/111 Pages) WOLFSON

59 / 111 page

Preliminary Technical Data

WM9713L

PTD, March 2004, Rev 2.2

TOUCHPANEL INTERFACE

The WM9713L 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.

Figure 16 Touchpanel Switch Matrix

PRINCIPLE OF OPERATION - FOUR-WIRE TOUCHPANEL

Four-wire touchpanels are connected to the WM9713L 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)

The principle of operation is illustrated below (Note: the illustrations assume that the top plate is used

for X and the bottom plate for Y measurements, although the reverse is also possible).

WM9713 Datasheet(PDF) 59 Page - Wolfson Microelectronics plc