SX8674ICSTRT datasheet(18/64 Pages) SEMTECH

18 / 64 page

ADVANCED COMMUNICATIONS & SENSING

Rev 1 – 25

th July 2011

www.semtech.com

SX8674/SX8675/SX8676

Haptics Enabled Multitouch 4/5-Wire

Resistive Touchscreen Controller with Proximity Sensing

Rxtot

Rytot

Figure 17 – Dual-touch Simplified Model

The two contacts create touch resistances Rt1 and Rt2 between the two layers of the touchscreen.

The SX8674/75/76 perform on-chip specific multitouch measurements which the host retrieves and processes

with a specific software enabling the detection of the gestures described in §13.3.

For optimum gesture detection, RmSelX and RmSelY parameters should be set according to table below.

X/Y Panel Resistance ( )

RmSelX/Y

100-187

000

188-312

001

313-938

010

939-1875

011

1876-4375

100

4376-9375

101

9376-18780

110

>18780

111

Table 5 – RmSelX/Y Selection Table

4.6

Digital Processing

The chip offers 4 types of data processing which allows the user to make trade-offs between data throughput,

power consumption and noise rejection.

The parameter FILT is used to select the filter order Nfilt. The noise rejection will be improved with a high order

to the detriment of power consumption. Each channel can be sampled up to 7 times and then processed to get a

single consolidated coordinate.

∑

−

⋅

≈

Figure 18 – Digital Processing Block Diagram

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