SX8674ICSTRT datasheet(37/64 Pages) SEMTECH

37 / 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

HAPTICS INTERFACE (SX8674/75)

6.1

Introduction

Haptics technology is commonly used in systems which include a touchscreen interface. Its purpose is to provide

tactile feedback to the user to acknowledge a touch event hence improving greatly the robustness of the system

and user comfort and perception.

The on-chip haptics interface is designed to drive two common actuator types: Eccentric Rotating Mass (ERM)

and Linear Resonant Actuator (LRA). This is performed without any external component due to fully embedded

analog processing and with very limited host interaction due to the embedded digital processing block.

Figure 48 – Haptics Interface Overview

The host configures drive parameters from the I2C port according to the particular haptics load to be used. The

haptics drive level is then controlled in real time by either of two methods: by a dedicated digital pin, MIN, which

accepts a pulse-width-modulated (PWM) digital signal; or by writing the desired output level directly to a register

via the I2C interface.

This digital information is filtered to prevent fast transitions and hence high current spikes (HAPTBW), converted

into the analog domain by an 8-bit DAC, and finally amplified (HAPTGAIN) to provide a differential signal

between MOUTP and MOUTN pins which can be directly connected to the motor thanks to their high drive

current capability.

For better isolation from the rest of the chip, the haptics interface analog block has its own power supply pins

MVDD and MGND.

The haptics interface is enabled when HAPTTYPEEN != 0.

6.2

ERM Load

6.2.1

Introduction

An ERM is a DC motor with an off-balance load to create a vibration. Speed and direction are controlled by the

applied voltage. The ERM load is selected when HAPTTYPEEN = 10.

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