Revision V1.7/October 2010

©2010 Semtech Corp.

SX8652

www.semtech.com

Page 11

ADVANCED COMMUNICATIONS & SENSING

DATASHEET

15kV ESD Low Power 4-Wire / 5-Wire Resistive

Touchscreen Controller with SPI Interface

3.2. Device Interface and ESD protection

The touch screen controller inputs have been specially designed to provide robust on-chip ESD protection of up to ±15kV

in both HBM and Contact Discharge.

3.2.1. Touchscreen interface

The X+/BR, X-/TL, Y+/TR,Y-/BL, AUX/WIPER are the pins dedicated for the touchscreen interface. It provides the voltage

sequence in order to obtain the coordinates and pressure measurement.

The five pins are connected to BR, TL, TR, BL, WIPER on a 5-wire touchscreen. They are the electrodes on the 4 corners

of the bottom layer of the touchscreen plus the electrode on the top layer.

On a 4-wire touchscreen, only 4 electrodes are used: X+,X-,Y+,Y-. The AUX pin is not needed and therefore can be used

to convert an analog signal (range GND - VDD) into 12-bit digital value. The touchscreen interface pins are the most

exposed pins for an ESD event.

As shown in Figure 7, theses pins have internal ESD protection to GROUND and VDD.

3.2.2. Host Interface and Control Pins

The SX8652 is a slave device configured via the SPI interface.

NIRQ provides an interrupt to the host processor when a pen is detected or when channel data is available. The NIRQ pin

is an active low, open drain output to facilitate interfacing to different supply voltages and thus requires an external pull-up

resistor (1-10 kOhm).

The host can reset the chip via the SPI interface or with the dedicated pin NRST. The NRST pin is an active low input that

provides a hardware reset. An internal pull-up enables the interfacing with devices at different supply voltage.

NRST and NIRQ pins are protected to GROUND.

Figure 7. ESD protection

T o u c h

S c r e e n

D r i v e r s

I n t e r f a c e

A

D

C

C o n t r o l

D a t a P r o c e s s in g

X + / B R

X - / T L

Y + / T R

Y - / B L

A U X /

W i p e r

M U X

P o w e r

M a n a g e m e n t

V D D

G N D

N R S T

N I R Q

S P I