Texas Instruments DRV2605EVM-CT Datenbogen
Input and output
Accleration
Ideal Open-Loop Waveform for Motor A
Output with feedback
Ideal Open-Loop Waveform for Motor B
Same simple input for
both motors
Feedback provides
optimum output drive
SLOS825C – DECEMBER 2012 – REVISED SEPTEMBER 2014
Feature Description (continued)
Figure 11. Waveform Simplification With Smart Loop
7.3.2.3.1
Startup Boost
To reduce the actuator start-time performance, the DRV2605 device has an overdrive boost feature that applies
higher loop gain to transient response of the actuator. The STARTUP_BOOST bit enables this feature.
higher loop gain to transient response of the actuator. The STARTUP_BOOST bit enables this feature.
7.3.2.3.2
Brake Factor
To reduce the actuator brake-time performance, the DRV2605 device provides a means to increase the gain
ratio between braking and driving gain. Higher feedback-gain ratios reduce the brake time, however, these ratios
also reduce the stability of the closed-loop system. The FB_BRAKE_FACTOR[2:0] bits can be adjusted to set the
brake factor.
ratio between braking and driving gain. Higher feedback-gain ratios reduce the brake time, however, these ratios
also reduce the stability of the closed-loop system. The FB_BRAKE_FACTOR[2:0] bits can be adjusted to set the
brake factor.
7.3.2.3.3
Brake Stabilizer
To improve brake stability at high brake-factor gain ratios, the DRV2605 device has a brake-stabilizer
mechanism
mechanism
that
automatically
reduces
the
loop
gain
when
the
braking
is
near
completion.
The
BRAKE_STABILIZER bit enables this feature.
7.3.2.4 Automatic Level Calibration
The smart-loop architecture uses actuator feedback by monitoring the back-EMF behavior of the actuator. The
level of back-EMF voltage can vary across actuator manufacturers because of the specific actuator construction.
Auto calibration compensates for this variation and also performs scaling for the desired actuator according to
the specified rated voltage and overdrive clamp-register settings. When auto calibration is performed, a 100%
signal level at any of the DRV2605 input interfaces supplies the rated voltage to the actuator at steady-state. The
feedback allows the output level to increase above the rated voltage level for automatic overdrive and braking,
but it does not exceed the programmable overdrive clamp voltage.
level of back-EMF voltage can vary across actuator manufacturers because of the specific actuator construction.
Auto calibration compensates for this variation and also performs scaling for the desired actuator according to
the specified rated voltage and overdrive clamp-register settings. When auto calibration is performed, a 100%
signal level at any of the DRV2605 input interfaces supplies the rated voltage to the actuator at steady-state. The
feedback allows the output level to increase above the rated voltage level for automatic overdrive and braking,
but it does not exceed the programmable overdrive clamp voltage.
In the event where the automatic level-calibration routine fails, the DIAG_RESULT bit in register 0x00 is asserted
to flag the problem. Calibration failures are typically fixed by adjusting the registers associated with the automatic
level-calibration routine or, for LRA actuators, the registers associated with the automatic-resonance detection
engine. See the
to flag the problem. Calibration failures are typically fixed by adjusting the registers associated with the automatic
level-calibration routine or, for LRA actuators, the registers associated with the automatic-resonance detection
engine. See the
section for automatic-level calibration programming .
Copyright © 2012–2014, Texas Instruments Incorporated
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