DRV2624 Datasheet, PDF (27/79 Pages) Texas Instruments – DRV2624 Ultra Low Power Closed-Loop LRA/ERM Haptic Driver with Internal Memory

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DRV2624
SLOS893A – DECEMBER 2015 – REVISED DECEMBER 2015
Programming (continued)
8.6.4 Programming for Open-Loop Operation
The DRV2624 device can be used in open-loop mode and closed-loop mode. If open-loop operation is desired,
the first step is to determine which actuator type is to use, either ERM or LRA.
8.6.4.1 Programming for ERM Open-Loop Operation
To configure the DRV2624 device in ERM open-loop operation, the ERM must be selected by writing the
LRA_ERM bit to 1, and the CONTROL_LOOP bit to 1.
8.6.4.2 Programming for LRA Open-Loop Operation
To configure the DRV2624 device in LRA open-loop operation, the LRA must be selected by writing the
LRA_ERM bit to 0, and the CONTROL_LOOP bit to 1. Additionally, the OL_LRA_PERIOD parameter must be
configured with the appropriate LRA frequency.
8.6.5 Programming for Closed-Loop Operation
For closed-loop operation, the device must be calibrated according to the actuator selection. When calibrated
accordingly, the user is only required to provide the desired waveform. The DRV2624 device automatically
adjusts the level and, for the LRA, automatically adjusts the driving frequency.
8.6.6 Diagnostics Routine
The DRV2624 has a diagnostic routine that can be selected by the MODE[1:0] parameter. The purpose of the
routine is to determine if the actuator can be safely and correctly driven. If a problem is detected by the
diagnostic routine, the DIAG_RESULT bit will assert (high). After running the diagnostic routine, the
DIAG_RESULT should be checked to assess the result of the diagnostic routine. If the diagnostic routine does
not finish due to a critical condition, such as a UVLO, over temperature or over-current condition, the diagnostic
routine will be aborted and the DIAG_RESULT will be set to 1.
The diagnostic routine is composed of 2 sub-routines: a resistance measurement routine and a functional
routine.
The resistance measurement sub-routine reports the resistance of the actuator as seen from the differential
output pins (OUT+ and OUT-) and placed on the DIAG_Z_RESULT parameter. The resistance measurement
sub-routine should always be executed during the diagnostics routine and the output is reported in the
DIAG_Z_RESULT. The only exception is during an over-temperature or UVLO condition, in which case the
diagnostic routine will abort immediately and the device will go into standby state.
NOTE
An over-current condition will never happen in this sub-routine, even in the presence of a
short, because the resistance measurement injects a small current that will not be
detected by the over-current detection circuit. The resistance measurement sub-routine is
the first to be executed. Also, this sub-routine will not cause the DIAG_RESULT bit to
assert.
After the resistance measurement, the diagnostic routine plays a diagnostic waveform to determine whether the
actuator can be successfully driven. A short or open condition, as well as failure to detect a valid BEMF will
cause the DIAG_RESULT bit to assert. Note that if a critical problem is experienced during the diagnostic
routine, such as an over-current condition, the routine can be aborted, and the DIAG_RESULT will assert.
8.6.7 Calibration Routine
The DRV2624 has a calibration routine that automatically populates all critical parameters required for
successfully driving a specific actuator (the one connected and being calibrated) in closed-loop. Variation occurs
between different actuators even if the actuators are of the same model. To ensure optimal results, TI
recommends that the calibration routine be run at least once for each actuator.
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