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DA7280

LRA/ERM Haptic Driver with Multiple Input Triggers,

Integrated Waveform Memory and Wideband Support

Datasheet

Revision 3.0

30-Jul-2019

CFR0011-120-00

21 of 76

When driving a wideband LRA in DRO mode, resonant frequency tracking can be turned off. This

enables wideband operation and two-dimensional effects using DMAs, see Sections 5.7.5 and 5.7.6.

During playback, if a value written to OVERRIDE_VAL results in the output driving strength being

maintained at 0 %, DA7280 will disable its output stage to save power. Drive is re-enabled

automatically, with one LRA half-period delay, when a non-zero OVERRIDE_VAL value I2C input is

received.

5.2.5

Pulse Width Modulation Mode

PWM mode is used to stream haptic sequences to DA7280 via the GPI_0/PWM input pin where the

output drive level is determined by the duty cycle of the PWM signal. For optimal start-up timing, the

PWM input signal needs to be provided before setting OPERATION_MODE = 2. The PWM duty

cycle can be interpreted in two ways as follows:

If ACCELERATION_EN = 1, the output drive level is equal to the input signal duty cycle multiplied by

the voltage stored in ACTUATOR_NOMMAX. In this case the duty cycle is interpreted as a

proportion between 0 % and 100 %, see Figure 30. The automatic Active Acceleration and Rapid

Stop (if enabled) features will take the output up to the voltage in ACTUATOR_ABSMAX and/or

reverse the drive level to be negative during level transitions, but in steady state the final value will

always scale to the voltage in ACTUATOR_NOMMAX.

If ACCELERATION_EN = 0, the output drive level is equal to the input signal duty cycle multiplied by

the voltage stored in ACTUATOR_ABSMAX. In this case the duty cycle is interpreted as a proportion

between -100 % and 100 % where 50 % duty cycle is 0 %, see Figure 31. When DA7280 is set up to

drive an ERM, the negative value represents a change in drive voltage polarity, while for an LRA it

represents a phase shift of 180° in the drive signal. Negative drive can be used to speed up output

acceleration level changes without the use of the Active Acceleration and Rapid Stop. Note that in

the ACCELERATION_EN = 0 case Rapid Stop can still be enabled if an automatic stop to zero

actuator acceleration is required.

Note: The output PWM frequency is always independent of the PWM input frequency regardless of

whether frequency tracking is enabled or disabled. To maximize accuracy and minimize power

consumption and noise, it is best to keep the input PWM frequency as low as possible.

The PWM demodulator is rising edge sensitive. The minimum duty cycle that can be used to create

the drive level can be configured in FULL_BRAKE_THR; any duty cycle below that value will produce

a 0 % drive level.

During playback streaming in PWM mode, if a 0 % drive level is maintained by applying a 0 % (or

50 % if Active Acceleration is disabled) duty cycle PWM input, the DA7280 output stage is disabled

to save power. Drive is re-enabled automatically, with one LRA half-period delay, when the duty

cycle forces the drive level to be greater than 0 %.

ACCELERATION_EN = 0,

60% Duty Cycle

ACCELERATION_EN = 0,

90% Duty Cycle

ACCELERATION_EN = 0,

50% Duty Cycle

ACCELERATION_EN = 0,

40% Duty Cycle

ACCELERATION_EN = 0,

10% Duty Cycle

PWM

Signal

DA7280

Output

Figure 9: Example PWM Inputs with ACCELERATION_EN = 0

Note the 180° phase difference between driving > 50 % and < 50 %.

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