DRV2625 Datasheet, PDF (14/77 Pages) Texas Instruments – DRV2625 Ultra Low Power Closed-Loop LRA/ERM Haptic Driver with Built-In Library

DRV2625
SLOS879A – DECEMBER 2015 – REVISED DECEMBER 2015
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Feature Description (continued)
8.3.4.1 Internal Memory Interface
The DRV2625 device has two internal-ROM libraries designed by Immersion called TS2200. The first library
works in closed-loop mode, and is designed for LRA actuators. The second library is specifically tuned for ERMs
operated in open-loop mode. If additional adjustments are required to the library effect to optimize performance
of a particular actuator model, the library parametrization parameters (ODT, SPT, SNT and BRT) can be used for
fine tuning. The library selection is done by the LIB_SEL bit.
LIBRARY
A
B
ACTUATOR
LRA Closed-Loop
ERM Open-Loop
Table 2. Library Table
RATED VOLTAGE
TBD
1.3 V
OVERDRIVE
VOLTAGE
TBD
3V
RISE TIME
AUTO
40 ms to 60 ms
BRAKE TIME
AUTO
20 ms to 40 ms
Using the internal library has several advantages including:
• Offloading processing requirements, such as digital streaming (RTP).
• Improving latency by only requiring a trigger signal.
• Reducing I²C traffic by eliminating the requirement to transfer waveform data
8.3.4.1.1 Library Parameterization
The waveforms stored in the internal library are augmented by the time offset parameters. This augmentation
occurs only for the waveforms stored in the internal library and not for RTP mode. The purpose of this
functionality is to add time stretching (or time shrinking) to the waveform. This functionality is useful for
customizing the entire library of waveforms for a specific actuator rise time and fall time.
The time parameters that can be stretched or shrunk include:
ODT
Overdrive time
SPT
Sustain positive time
SNT
Sustain Negative Time
BRT
Brake Time
The time values are additive offsets and are 8-bit signed values. The default offset of these values is 0. Positive
values add and negative values subtract from the time value of the effect that is currently played. The most
positive value in the waveform is automatically interpreted as the overdrive time, and the most negative value in
the waveform is automatically interpreted as the brake time. These time-offset parameters are applied to both
voltage-time pairs and linear ramps. For linear ramps, linear interpolation is stretched (or shrunk) over the two
operative points for the period.
t_(final) = t_(orig) t_(ofs)
(4)
8.3.4.1.2 Playback Interval
The internal memory ticks are by default interpreted as 5-ms intervals. if additional granularity is desired, then a
1-ms interval can be selected by using the PLAYBACK_INTERVAL bit.
8.3.4.1.3 Waveform Sequencer
The waveform sequencer queues waveform identifiers for playback. Eight sequence registers queue up to eight
waveforms for sequential playback. A waveform identifier is an integer value referring to the index position of a
waveform in the internal library. Once the user has selected the Waveform Playback as the process to run in the
MODE[1:0] parameter, playback begins at WAV_FRM_SEQ1 when the user triggers the process (either with the
GO bit or externally, if configured to do so). When playback of that waveform ends, the waveform sequencer
plays the waveform identifier held in WAV_FRM_SEQ2 if the next waveform is non-zero. The waveform
sequencer continues in this way until it reaches an identifier value of zero or until all eight identifiers are played,
whichever scenario is reached first.
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