sx8652 Semtech Corporation, sx8652 Datasheet - Page 13

• Manufacturer Part Number: sx8652
• Description: 15kv Esd Low Power 4-wire / 5-wire Resistive Touchscreen Controller With Spi Interface
• Manufacturer: Semtech Corporation

4. 4-wire Touch Screen Detailed Description
4.1. Touch Screen Operation
A 4-wire resistive touch screen consists of two (resistive) conductive sheets separated by an insulator when not pressed.
Each sheet is connected through 2 electrodes at the border of the sheet (Figure 12). When a pressure is applied on the top
sheet, a connection with the lower sheet is established. Figure 13 shows how the Y coordinate can be measured. The
electrode plates are connected through terminals X+, X- and Y+, Y- to an analog to digital converter (ADC) and a reference
voltage. The resistance between the terminals X+ and X- is defined by Rxtot. Rxtot will be split in 2 resistors, R1 and R2, in
case the screen is touched. The resistance between the terminals Y+ and Y- is represented by R3 and R4. The connection
between the top and bottom sheet is represented by the touch resistance (R
Revision V1.6/July 2010
©2010 Semtech Corp.
ADVANCED COMMUNICATIONS & SENSING
Vref
electrodes
+
-
Figure 13. Touch Screen Operation ordinate measurement (Y)
X-
R2
Figure 12. 4-wire Touch Screen
X-
R4
Y+
Y+
Y-
15kV ESD Low Power 4-Wire / 5-Wire Resistive
R
R3
T
Page 13
Y-
bottom conductive sheet
Touchscreen Controller with SPI Interface
R1
X+
top conductive sheet
X+
T
).
electrodes
+
-
ADC
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SX8652
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