wm9712l Wolfson Microelectronics plc, wm9712l Datasheet - Page 38

• Manufacturer Part Number: wm9712l
• Description: Ac?97 Audio And Touchpanel Codec
• Manufacturer: Wolfson Microelectronics plc

WM9712L
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TOUCHPANEL INTERFACE
PRINCIPLE OF OPERATION - FOUR-WIRE TOUCHPANEL
The WM9712L includes a touchpanel driver and digitiser circuit for use with 4-wire or 5-wire resistive
touchpanels. The following functions are implemented:
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•
•
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•
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 5 Touchpanel Switch Matrix
Four-wire touchpanels are connected to the WM9712L as follows:
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•
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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)
Right side contact = X+ (pin 14)
Left side contact = X- (pin 16)
Top side contact = Y+ (pin 15)
Bottom side contact = Y- (pin 17)
I
P
R
20K
PU
comparator
zero power
10K
SAR
ADC
DOWN
PEN
PD Rev 4.5 August 2006
Production Data
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