Industry’s Most Highly Integrated Piezo Haptic DriverEric Siegel

Product Marketing Engineer, Touch Screen Controllers and Haptics

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What is Haptics?• Touch screens are replacing traditional user interfaces

• Touch screens have one major disadvantage– No physical or mechanical feedback when

the screen is pressed or an event occurs– Loss of tactile or haptic feedback

• The solution is haptics….– Haptics refers to the sense of touch and is a

technology that provides mechanical feedback through the use of vibrations to simulate specific events or effects.

• Benefits of Haptics– Improves task performance – Increases user satisfaction – Provides a more realistic experience

Cell Phones & Handhelds Tablets

Laptops & Desktops Portable Gaming Devices

Touch ecosystem

Touch Panel and Display

Applications Processor/Chipset reference design

HapticsSW

TSC

Haptics Driver

Touch Location

Haptics effects

Haptics actuators

HapticsSW

Touch Screen

Controller

Haptics Driver

Note: Haptics Software stored in only one of two locations

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Piezo actuator-based haptics

• Enables high-definition and localized Haptics effect generation

• Piezo actuators are very thin (<1mm)

• Piezo actuators are either single-layer or multi-layer– Single Layer

• Need up to 200 Vp-p to drive• More cost effective• Have low capacitance and can be driven with lower current

– Multi-layer• Need up to 50Vp-p to drive multi-layer piezos• Cost scales linearly with the number of piezo layers• Have high capacitance and needs higher current drive

Introducing the DRV8662

•High analog integration (boost converter, diode)–50% smaller solution size than leading competition

•Does not need an external transformer–40% lower system solution cost than leading competition

•Analog input –Can be driven by DAC or filtered pulse width modulation

(PWM)•GPIO gain control

–Supports wide range of piezo actuator voltages•50-200 - volt peak to peak (Vpp) differential outputs

–Drive high-definition inaudible haptics effects•Haptics frequencies up to 500-Hz

–Enables wide variety of high-resolution haptics effects

Industry’s most integrated single-chip piezo haptic driver

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Feel the difference

• Get haptic feedback from the smallest actions onscreen

• Feel each time your “bird missile” ruffles its feathers or slams into the wooden blocks

• Localized responses on the screen

• Pluck a string on your guitar app and feel the frequency associated with that string, in the exact spot you’re touching

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Applications

Actuator response

Inertial • Low bandwidth

• Start-up and response times are slower

• Lower bandwidth limits types of effects

• Motor (ERM) or linear actuator (LRA)

• DRV8601

Piezo• High bandwidth

• Fastest response time and largest bandwidth

• Wider range of effects

• Piezo bender or piezo module

• DRV8662

Response and accuracy of haptics effects

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Frequency

Streng

th

LRAdirect drive

ERMspinning

ERM/LRApulsing

Bandwidth profilesPiezo actuators offer higher bandwidth than inertial actuators

50Hz 175Hz 300Hz

<1ms ~30-60ms

Faster response time Piezo (DRV8662)

ERM, LRA

Response time of the DRV8662Inertial Actuators vs. Piezo Actuators

Time

Streng

th

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Competition vs. DRV8662

FlybackSolutionBaseband

1:N

R3

EN

IN+

IN-

VBAT

SW

FB

GATE

SOURCE

GND

BATTERY VOLTAGE

R2

R1

C2

C1

HapticPiezo

Competition’s flyback solution TI DRV8662 Integrated, high-voltage process solution

• Low voltage process

• Transformer – bulky, expensive

• External FET

• External eiode

• Difficult charge/discharge control schemes that are separated

• Total board space ~200mm2

• High voltage process

• Transformer-less

• Integrated FET

• Integrated diode

• Simple Op-Amp voltage controlled feedback allowing adjustable gain

• Total Board Space ~100mm2

DRV8662 evaluation kit

Touch panel glass with Piezo Actuator assembly

DRV8662 MSP430G2253

Complete Haptics Evaluation• I2C Interface through MSP430

• Analog / PWM input option to the DRV8662 with I2C bypass

• Programmable MSP430 with sample code

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Summary

Small solution size

50 to 200-Vpp differential drive

Flexible architecture

Low solution cost

50% smaller with no external transformer

40% lower cost with no expensive external transformer

High-definition haptics effects

Can drive single or multi-layer piezo actuators

For your readers

• DRV8662 Product Folder– www.ti.com/drv8662-pr

• “What is haptics?” video– www.ti.com/drv8662video-pr

• Technical support for touch products– www.ti.com/touchforum-pr

Thank You