VDD

GND

LRA or

DC Motor

VDD

C

R

OUT-

OUT+

IN2

REFOUT

IN1

EN

DRV8601

SE PWM

Shutdown

Control

10k

47k

2k

R

I

R

F

C

F

+

–

PWM

F

O,DIFF

IN

I

F

F

R

V

1

V

=

V

2

R

1 + sR C

æ

ö

-

´

´

ç

÷

è

ø

DRV8601

www.ti.com

SLOS629B

– JULY 2010 – REVISED JANUARY 2012

PSEUDO-DIFFERENTIAL FEEDBACK WITH LEVEL-SHIFTER

This configuration is desirable when a regulated supply voltage for the DRV8601 (VDD) is availble, but that

still recommended in this scenario. If the supply voltage varies, the PWM level shifter output will follow, and this

will, in turn, cause a change in vibration strength. However, if the variance is acceptable, the DRV8601 will still

operate properly when connected directly to a battery, for example. A 50% duty cycle will still translate to zero

voltage of VDD is achieved when the PWM duty cycle is set to 100%.

Figure 16. Pseudo-Differential Feedback with Level-Shifter

DIFFERENTIAL FEEDBACK WITH EXTERNAL REFERENCE

This configuration is useful for connecting the DRV8601 to an unregulated power supply, most commonly a

battery. The gain can then be independently set so that the required motor overdrive voltage can be achieved

above. Note that VDD must be greater than or equal to the desired overdrive voltage. A resistor divider can be

drawn by the divider in shutdown.

In this configuration, feedback is taken from both output pins. The output voltage is given by Equation 3 (where s

(3)

Note that this differs from Equation 1 for the pseudo-differential configuration by a factor of 2 because of

the PWM frequency in order to eliminate the PWM frequency and its harmonics from entering the motor. This is

desirable when driving motors which do not sufficiently reject the PWM frequency by themselves. When driving a

low-pass cutoff frequency is higher than the resonant frequency of the linear vibrator.

Copyright

© 2010–2012, Texas Instruments Incorporated

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