DA7281-00FVC datasheet(40/76 Pages) DIALOG

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DA7281

LRA/ERM Haptic Driver with Multiple I²C Addresses,

Integrated Waveform Memory, and Wideband Support

Datasheet

Revision 3.0

30-Jul-2019

CFR0011-120-00

40 of 76

● IMAX now corresponds to twice the value computed by the formula in Section 5.6.2.

● When setting the impedance in V2I_FACTOR_H and V2I_FACTOR_L via the formula in Section

5.6.2, use Zformula = 2*Zreal.

● When reading back from IMPEDANCE_H and IMPEDANCE_L, use an LSB of 0.03125 Ω.

5.7.13

Supply Monitoring, Reporting, and Automatic Output Limiting

DA7281 monitors the level of the supply during playback and reports it via ADC_VDD_H and

ADC_VDD_L. The two should be concatenated and read using the following formula:

�� = (��_��_�� × 128 + ��_��_��) × 0.1831 ��

(13)

DA7281 uses this information to prevent the device from clipping to supply by limiting the drive to a

value determined by the VDD_MARGIN register in 187.5 mV steps where 0x0 corresponds to no

margin, see Figure 22.

Output drive clipping to

VDD – VDD_MARGIN, not ABSMAX

Time [s]

VDD

ABSMAX

VDD - VDD_MARGIN

VDD_MARGIN

Figure 22: Automatic Output Limiting

The functionality is needed as DA7281 regulates current and if supply clipping occurs, the regulation

stops and the BEMF information is lost. Furthermore, the VDD_MARGIN register allows limiting of

the power across the actuator for low supply values to prevent the battery from discharging too fast.

5.7.14

BEMF Fault Limit

To detect malfunctioning actuators that have stopped moving due to a mechanical fault, DA7281 can

be configured to trigger an actuator fault if the BEMF voltage level falls below a threshold for long

drive durations. The threshold for detection is set in BEMF_FAULT_LIM; a zero value of the register

disables the fault checking.

5.7.15

Increasing Impedance Detection Accuracy

To increase the accuracy of the impedance reading in IMPEDANCE_H and IMPEDANCE_L, the

the acceleration algorithm. Should V2I_FACTOR_OFFSET_EN be equal to 0, ACCELERATION_EN

is recommended to be set to 0.

5.7.16

Frequency Pause during Rapid Stop

To address low mechanical time constant LRAs (start/stop times less than 20 ms) and improve the

braking behavior, DA7281 has the option to pause frequency tracking during the execution of the

Rapid Stop algorithm by setting FRQ_PAUSE_ON_POLARITY_CHANGE to 1.

DA7281-00FVC Datasheet(PDF) 40 Page - Dialog Semiconductor

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