DRV8601: PWM Frequency and Rms 1.8V haptic driving

Hi Onur,

First of all I'd like to recommend you to look into our newer actuator drivers from DRV26xx family (DRV2625/DRV2624).
These devices have the ability to sense the back-EMF from the actuator to identify LRA resonance frequency and drive the actuators in an enhanced closed-loop mode called smart-loop, among other features.

Could you share your schematic? The outputs should drive the input voltage times the gain of the circuit. The PWM you mention seems to be correct. Have you tried to drive your actuator already? What is the result?

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Hi Ivan,

Thanks for your suggestion. I did my own demo board . I tried both (DRV2605 and DRV8601).

DRV2605 raises the cost. It's successful.The only problem is that it will increase the cost. I also can't use a BGA case.

I couldn't get enough information on DRV8601 datasheet. What should be the PWM frequency? I checked the output frequency of the DRV2605. The frequency was quite high. Should the control frequency be high?

10 KHz, 20 KHz etc.?

Is the optimal feed for the LRA I use is Vrms * 1.414 (Vrms 1.8V)?

Onur,

DRV2605L has VSSOP package, you could consider this part.

Regarding the PWM modulation frequency, it would depend on the actuator you're driving. Basically the actuators only "see" the average of the PWM signal, so if PWM frequency is too low, the actuator could be fluctuating around the average value. By increasing the PWM frequency the average "variation" is reduced. Different motors have different time constants. Specifically talking about LRAs, you need a PWM frequency high enough for LRA resonance frequency to be "seen" as stable as possible, same as motors.
You can try with DRV2605 PWM frequency ~20kHz.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Onur,

I'm following up on this thread.
Do you got further questions? Is your application working fine?

Thanks and Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Ivan,

Before closing to topic ; You said, "You can try with DRV2605 PWM frequency ~ 20kHz". There may be a misunderstanding. I applied 20KHz pwm to 8601. It seems good.

We haven't talked about the supply voltage yet. As I asked before;

Is the optimal supply voltage for the LRA I use is Vrms * 1.414 (Vdd = 2.5V for Vrms 1.8V)?

I tested it with two different voltages (5V and 3.3V). Will the LRA be damaged at these voltages? What is the ideal situation?

Hi Ivan,

Thanks for your attention. That's what I wanted to learn.