DRV2605L-Q1 Datasheet, PDF (13/67 Pages) Texas Instruments – Automotive Haptic Driver for LRA and ERM

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DRV2605L-Q1
SLOS874A – OCTOBER 2015 – REVISED OCTOBER 2015
Feature Description (continued)
7.3.3 Open-Loop Operation for LRA
In the event that open-loop operation is desired (such as for off-resonance driving) the DRV2605L-Q1 device
includes an open-loop LRA drive mode that is available through the PWM input or through the digital interface.
When using the PWM input in open-loop mode, the DRV2605L-Q1 device employs a fixed divider that observes
the PWM signal and commutates the output drive signal at the PWM frequency divided by 128. To accomplish
LRA drive, the host should drive the PWM frequency at 128 times the desired operating frequency.
When activated, the digital open-loop mode is available for pre-stored waveforms as well as for RTP mode. The
OL_LRA_PERIOD bit in register 0x20 programs the operating frequency, which is derived from the PWM output
frequency, ƒ_O(PWM). Use Equation 1 to calculate the driving frequency. The open-loop mode does not receive the
benefits of the smart-loop architecture.
7.3.4 Open-Loop Operation for ERM
The DRV2605L-Q1 device offers ERM open-loop operation through the PWM input. The output voltage is based
on the duty cycle of the provided PWM signal, where the OD_CLAMP[7:0] bit in register 0x17 sets the full-scale
amplitude. For details see the Rated Voltage Programming section.
7.3.5 Flexible Front-End Interface
The DRV2605L-Q1 device offers multiple ways to launch and control haptic effects. The MODE[2:0] bit in register
0x01 is used to select the interface mode.
7.3.5.1 PWM Interface
When the DRV2605L-Q1 device is in PWM interface mode, the device accepts PWM data at the IN/TRIG pin.
The DRV2605L-Q1 device drives the actuator continuously in PWM interface mode until the user sets the device
to standby mode or to enter another interface mode. In standby mode, the strength of vibration is determined by
the duty cycle.
For the LRA, the DRV2605L-Q1 device automatically tracks the resonance frequency unless the
LRA_OPEN_LOOP bit in register 0x1D is set. If the LRA_OPEN_LOOP bit is set, the LRA is driven according to
the frequency of the PWM input signal. Specifically, the driving frequency is the PWM frequency divided by 128.
7.3.5.2 Internal Memory Interface
The DRV2605L-Q1 device has seven internal-ROM libraries designed by Immersion called TS2200. The first five
libraries and the last library are specifically tuned for six categories of ERMs operated in open-loop mode (see
Table 1). Library 6 is a closed-loop library tuned for LRAs. The library selection occurs through register 0x03 (see
the (Address: 0x03) section).
ERM Library A
LIBRARY_SEL[2:0] = 1
ERM Library E
LIBRARY_SEL[2:0] = 5
LRA Library
LIBRARY_SEL[2:0] = 6
ERM Library F
LIBRARY_SEL[2:0] = 7
Figure 12. Library Selection
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