As more OEM designs move away from button or switch interfaces to haptic feedback, there is growing demand for advanced haptic technologies that deliver an easier way to create “virtual” buttons across a variety of applications, from smartphones to automotive. Cirrus Logic Inc. believes that it has the answer to this challenge with the new CS40L25 haptic driver solutions for driving high-performance linear resonant actuators (LRAs) and voice coil motors (VCMs).
The CS40L25 devices integrate a high-performance haptic driver, a digital signal processor (DSP), and a boost converter. The programmable DSP runs real-time algorithms with low latency and offers a larger memory for more haptic effects — storing more than 50 programmable waveforms in RAM. The ultra-low-power (<20-μA sleep mode) CS40L25 devices also support always-on listening for haptic trigger.
The Class H digital boost converter provides 85% overall efficiency boost and programmable boost voltages up to 11 V. Other features include a high-bandwidth digital control loop, 2-MHz switching frequency, and pulse-skipping mode for improved efficiency during low-power quiescent operation.
Cirrus Logic’s CS40L25 boosted haptic solution integrates a high-performance haptic driver, a digital signal processor, and a driver voltage boost converter, delivering enhanced user experiences for a variety of applications, including mobile, automotive, PCs, wearables, and gaming/VR.
Leveraging its low-power, low-latency, and mixed-signal–processing technology, Cirrus Logic’s new family of boosted haptic drivers are designed to enable richer, immersive user experiences. The new devices are available in several variants to meet a variety of applications, including mobile/portable devices, PCs/laptops, and automotive.
“Haptic technology is literally in billions of people’s hands every day,” said Shahram Tadayon, product marketing manager, at Cirrus Logic. “A few years ago, cellphone manufacturers started removing the home button and instead replaced it with a virtual button, and it provided a nice, sleek, buttonless design and also a nice sharp click.
“Since then, more and more cellphone manufacturers have removed that button and added virtual buttons,” he added. “In addition to just virtual buttons for cellphones, haptics has gone beyond that into wearables, into PC track pads, and into automotive for touchscreens. And these all started off with a simple click, but within the next few years, you’re going to start seeing more and more gestures incorporated into haptics as well.”
A complete solution
Cirrus Logic differentiates its solution by offering a complete haptic driver solution that includes the hardware, firmware, and tools. One thing that makes the solution unique compared to a lot of others is that not only is Cirrus Logic incorporating the hardware — driving the actuator — but it is also incorporating the DSP algorithms, said Tadayon. “Generally, you’ll find that the driver for the actuator doesn’t provide the algorithms and the different firmware.
“We also offer tools that quickly enable customers to provide their own sensation or feeling for the haptics,” he said. “We make it easy for them to modify the haptics with the tools and the hardware and the software, so we really provide a full package for them.”
The waveform creation tools go beyond the virtual button click to provide effects like scrolling or a zoom pinch, said Tadayon. The solution can recreate any of the familiar buttons using almost any actuator that is an LRA or VCM type, he added.
The haptic waveforms include virtual button clicks, scrolling, sensor effects, haptic bumps, high-fidelity alerts, and camera clicks. A ringtone builder is also included.
Tadayon said that there is a lot of engineering that goes into making a haptic effect that the brain perceives to be a button. A great haptic solution needs a boost converter, a closed-loop system, and low latency, he said, enabling customized waveforms for a variety of haptic feedback responses that deliver a crisp and strong feel for a better user experience.
The solution’s ultra-low latency (<5 ms for GPI trigger) provides real-time control of the haptic motor to provide users with a more immediate sensation or response, while the closed-loop algorithms maximize the LRA with a “crisper” effect and simplify the tuning.
“Haptics is generated from an actuator, usually an LRA that moves back and forth quickly,” said Tadayon. “It’s important for the haptic driver IC to have enough voltage to drive this quickly for a strong response. Many applications such as phones and wearables have low-voltage batteries, so it’s important that the technology has a boost converter to drive the voltages higher to make that strong, sharp feeling.”
By having a boost voltage that goes up to 11 V, it ramps up that actuator very quickly and allows it to have a fast, crisp feel, he added. “But what’s just as important is to be able to stop an actuator from moving very fast, and for that, we have a closed-loop algorithm. So we’re constantly monitoring the position of the actuator, and we can make it stop very quickly, and that’s what gives it that sharp feel.”
The most important aspect of a design is having a sharp and strong feel, said Tadayon, which is thanks to the company’s boosted technology and closed loop-algorithm. This means stopping that LRA as quickly as possible, which can be achieved through the DSP and closed-loop algorithms, and it needs to happen fast — within 25 milliseconds, he said.
“From the time when you press the screen to when your finger feels the haptics sensation, if that’s within 25 ms, it feels like a real button click,” he said. “So having that fast latency is really important. Once you’ve started getting beyond 50 ms, then your brain knows something’s not quite right. This doesn’t feel like a real button.”
Cirrus Logic’s chip was designed to react within 4 ms, which Tadayon attributes to the waveforms stored in memory and the boosted driver.
In addition, instead of having the microcontroller do all the heavy lifting, which takes time and impacts latency, the haptics solution can store 50 different and customizable waveforms (effects) in RAM thanks to “a good amount of internal memory.”
Cirrus Logic developed several variants to address different product applications. These include the CS40L25-CWZR and CS40L25B-CWZR ICs in 30-ball WLCSP packages for mobile and portable applications, which are now shipping in volume. The commercial-grade CS40L25B-CNZR in a 32-pin QFN product addresses PC/laptop and other general market applications, while the automotive-qualified CS40L25B-DNZ AEC-Q100 in a 32-pin QFN package with wettable flanks is designed for infotainment applications such as touch buttons and touchscreens. Both the commercial-grade and automotive-qualified devices are sampling.
“Over the next several years, more and more users are going to experience a richer experience with their electronics,” said Tadayon. The company’s roadmap includes bringing in integrated force-sensing technology along with the haptics and algorithms to reduce size, power consumption, and latency.
>> This article was originally published on our sister site, Electronic Products.