DA7280-Automotive

Wideband LRA/ERM Haptic Driver for Automotive

Applications

Datasheet

Revision 1.4

01-Mar-2022

CFR0011-120-00

36 of 79

© 2022 Renesas Electronics

5.7.3

Initial Impedance Update

DA7280-A performs an impedance measurement at the very first half-period of drive at the start of

playback. This allows a one-shot update of V2I_FACTOR_H/L to take into account specific actuator

variation for increased voltage accuracy of the drive. The result is reported to IMPEDANCE_H/L,

which can be read by the host and converted to impedance using the following formula:

������������������������������������������������ ������������������������������������������������������(������������������������������������������) = (������������������������������������������������������_������ × 4 + ������������������������������������������������������_������) × 0.0625Ω

(12)

To disable this feature, set V2I_FACTOR_FREEZE and CALIB_IMPEDANCE_DIS = 1.

5.7.4

Amplitude PID

Some cylinder based ERMs generate excessively large-amplitude BEMF voltages. DA7280-A can

compensate for this by reducing the drive current level, set AMP_PID_EN = 1. The result is an

improved haptic response. Figure 17 describes how the actuator voltage and current differs when

AMP_PID_EN enabled or disabled.

Time [s]

VOUT

IOUT

AMP_PID_EN = 0

Time [s]

BEMF Voltage

Time [s]

VOUT

IOUT

AMP_PID_EN = 1

Time [s]

IOUT drops automatically to compensate

BEMF and keep VOUT constant

Figure 17: Output Voltage and Current for Different AMP_PID_EN Values

Note: This is not usually required for LRAs as the amplitude of the BEMF is typically very low.

5.7.5

Wideband Operation

DA7280-A natively supports wideband LRAs and allows continuous frequency updates to the output

signal while driving. Amplitude and frequency data use parallel data paths, for configuration see

Section 5.6.5. This section describes how to use the frequency component only.

For wideband operation, frequency tracking must be disabled, by setting FREQ_TRACK_EN = 0,

because drive at frequencies different from the actuator resonant frequency is required. Rapid Stop

and Active Acceleration also rely on frequency tracking so must be deactivated by setting

ACCELERATION_EN = 0 and RAPID_STOP_EN = 0. There are two ways to operate DA7280-A

during wideband operation:

● In the limited frequency range of 25 Hz to 300 Hz:

○ No further settings are required in RTWM and ETWM modes if the frequency information is

already stored in the Waveform Memory frame data as described in Section 5.8.3. If the

Waveform Memory does not contain frequency information, then each sequence can be

played at a different frequency by setting LRA_PER_H and LRA_PER_L to the desired value

via the formulae in Section 5.6.2 before triggering playback using the method described in

Sections 5.6.5.4 and 5.6.5.5.

○ In the DRO and PWM modes, the frequency information can be updated via the LRA_PER_H

and LRA_PER_L using the formulae in Section 5.6.2 either before triggering playback of

each sequence, see Sections 5.6.5.2 and 5.6.5.3, or during the playback itself. As with

amplitude, the one half-period uncertainty on the output frequency update also applies.

● In the full range of 25 Hz to 1024 Hz, the same procedures apply for all modes, but the following

registers need to be set:

○ BEMF_SENSE_EN = 0