DRV2603_14 Datasheet, PDF (9/19 Pages) Texas Instruments – Haptic Drive with Auto-Resonance Detection for Linear Resonance Actuators (LRA)

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DRV2603
SLOS754A – JUNE 2012 – REVISED JANUARY 2014
ECCENTRIC ROTATING MASS MOTORS (ERM)
Eccentric Rotating Mass motors, or ERMs, are typically DC-controlled motors of the bar or coin type. ERMs can
be driven in the clockwise direction or counter-clockwise depending on the polarity of voltage across its two
terminals. Bi-directional drive is made possible in a single-supply system by differential outputs that are capable
of sourcing and sinking current. This feature helps eliminate long vibration tails which are undesirable in haptic
feedback systems..
Figure 13. Reversal of Motor Direction
Another common approach to driving DC motors is the concept of overdrive voltage. To overcome the inertia of
the motor's mass, they are often overdriven for a short amount of time before returning to the motor's rated
voltage to sustain the motor's rotation. Negative overdrive is also used to stop (or brake) an ERM quickly by
reversing the magnetic field of the driving coil(s).
ERM MODE
The DRV2603 is a compact, cost-effective driver solution for ERM motors. Most competing solutions require
external components for biasing or level-shifting, but the DRV2603 requires only one decoupling capacitor giving
a total approximate circuit size of 2 mm by 2 mm. This small solution size still comes packed with features such
as a level-shifted input, differential outputs for braking, constant drive strength over supply, edge rate control, and
a wide input PWM frequency range.
When in ERM mode, the DRV2603 employs a simple control scheme. A 100% input duty cycle gives full-strength
forward rotation, a 50% input duty cycle give no rotation strength, and a 0% duty cycle give full-strength reverse
rotation. Forcing the motor velocity towards reverse rotation is used to implement motor braking in ERMs. By
stringing together various duty cycles over varying amounts of time, a haptic motor control signal will be
constructed at the output to precisely drive the motor.
Output Drive
3.3 V
0V
-3.3 V
0%
Copyright © 2012–2014, Texas Instruments Incorporated
50%
PWM Input Duty Cycle
Figure 14. ERM Mode
Product Folder Links :DRV2603
Input
100%
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