Since the popularization of haptic feedback, many application scenarios have been derived. After being completely popularized by smartphones, new opportunities have been found in VR/AR. Whether it is ERM, LRA or piezoelectric, it is inseparable from the key IC, tactile sensor. So in the haptic feedback experience we are pursuing today, in addition to the haptic driver requiring good performance, there are actually many pain points, such as the introduction of touch feedback increases power consumption, or lacks a real high-quality experience. These pain points can also be seen in the products of haptic driver manufacturers, and they also want to try their best to solve these problems.
How low power consumption is low
Dialog’s DA728x series is a haptic driver for LRA and ERM. There are three products: DA7280, DA7281 and DA7282. The main products are low power consumption and high resolution, but the positioning is different. All three products support a wideband LRA frequency range of 25Hz to 1kHz, resonant frequency tracking up to 300Hz, plus 0.75ms wake-up delay, the performance is sufficient for haptic feedback applications in mobile phones, notebooks, automotive and industrial fields. The DA7281 has multiple I2C addresses, so multiple (4) DA7281 devices can be used in the same system.
DA7280 / Dialog
As for Dialog’s DA7282, it is a haptic driver featuring ultra-low power consumption and high bandwidth. Unlike the DA7280 and DA7281 of the same series, the DA7282 supports entering a full standby mode, reducing the standby current to a limit of 5nA, and even in the idle state, the standby current is only 0.68µA.
This is tens of times smaller than typical haptic drivers with µA standby current, which is critical for systems powered by small batteries. To reduce system complexity, the DA7282’s integrated waveform memory allows it to be preloaded with haptic sequences, and can also be input via external sources such as I2C or PWM signals.
Audio to Haptics
Nowadays, the vibration on mobile phones may be the tactile feedback that we feel the most and most frequently in our daily life. Many mobile phone manufacturers will also advocate the linear motors they use when promoting. However, the Pixel 6 and Pixel 6 Pro models launched by Google last year have a quite noteworthy feature, that is, the so-called “audio coupled haptic effect” was introduced in the official version of Android 12 that came with it. Translating into haptic effects, which improve the quality of haptic feedback, users can also control the frequency and amplitude of vibrations more finely.
There are two reasons why such precise haptic feedback control can be achieved. One is the new haptic API and haptic generator (HapticGenerator) introduced by Google in Android 12, which acts as an audio post-processor and can generate haptic data through channels. Second, this function must also be supported by hardware. It can be seen from some dismantling videos that Google has used CirrusLogic’s CS40L25 in the Pixel6 series. This IC supports audio-2-haptics, which is also called Audio to haptic functionality.
CS40L26 / CirrusLogic
CirrusLogic also introduced the CS40L26 series of haptic driver ICs that support non-inductive rate control. This series integrates DSP and Class D digital boost converter, and also provides full compatibility with Android 12. With the support of 130MHz programmable DSP, CS40L26 can provide advanced closed-loop control of LRA motor, which can provide functions such as real-time braking, LRA consistent acceleration and vibration pattern generation. The sensorless rate control can not only achieve real-time dynamic adaptation to the LRA, optimize applications that require continuous haptic feedback, but also increase the relatively weak bandwidth of the LRA.
Some Thoughts on Haptic Feedback
Dialog’s DA7282 achieves the ultimate standby power consumption, which is even lower than that of piezoelectric drivers. It can make full use of the advantages of LRA in wake-up time. Coupled with the optional WLCSP-12 and QFN-12 packaging methods, DA7282 can be said to be a product born for applications such as smart wear. As for CirrusLogic’s haptic driver, it has added support for audio serial ports, which can be said to be a great tool for improving the touch experience for the Android phone lineup. It is hoped that more manufacturers’ haptic drivers will introduce similar designs in the future.
In fact, for most haptic feedback schemes, it is not only the haptic driver that is important, but also the adjustment of the control scheme. After all, the so-called high-quality tactile feedback today is not the one whose vibration amplitude is greater, but the spelling of “intelligence” and “adaptive”. In this regard, game console hardware manufacturers have obviously gone further. From the trigger vibration of Microsoft’s Xbox handle, to the HD vibration of Nintendo’s Switch Joy-Con, to the more delicate adaptive vibration of Sony’s PS5 handle, all of them are a haptic feedback. Another upgrade.
Of course, we can attribute these to the size of the motor, or the use of voice coil motors, but like the transition from stereo to multi-channel audio, multi-dimensional haptic feedback can get the best experience, which is why the host The reason why hardware manufacturers will start with a variety of peripherals. As a mobile phone or smart watch, as an independent device, it will inevitably be limited by volume, sensors, etc. in realizing the vibration effect, and it is understandable to use some general haptic feedback solutions. After all, one of the attributes of the mobile phone itself is versatility. It is obviously more difficult to make the system and software adapt to tactile feedback other than sliding, touch and other operations. Because of this, how to achieve multi-dimensional tactile feedback in mobile phones must find another way. As mentioned above, audio-to-vibration is a good example.
Isn’t everything involved in the “metaverse” now, and the development of haptic feedback is no exception. In the future, haptic feedback is likely to develop into touch without physical interaction, but simulate this process by stimulating electrical signals from nerves. However, this so-called “super-modal touch” is still in a relatively early experimental stage, and most of them are also used in medical scenarios, and most of them are invasive technologies. Who knows? Perhaps the development of brain-computer interfaces in the future will bring a higher-quality touch experience.