Mobile Display – Patrick Worfolk, CTO, Synaptics delivered a talk on the firm’s views and approach for touch and display driver integration at Touch Gesture Motion 2014 in Austin, Texas, October 28-30, 2014.
Worfolk commenced his presentation reporting that the firm’s FY14 revenue will be approximately $1.6 billion as Synaptics’ delivers its touch technology to the smartphone, tablet, notebook PC and automotive markets.
Worfolk’s talk centered on the past, present and future of touch sensing and display integration. He reviewed the stack-ups of discrete, on-cell and in-cell touch sensing approaches contrasting the strengths of the discrete versus integrated approaches. The discrete touch sensor approach is a proven, low-risk technology and supports the independent fabrication of separate touch sensor and display modules. However, the display integrated touch approach delivers thinner, lighter displays, better optics, lower cost and a simplified supply chain. Worfolk pointed out that in 2015 over half of all smartphones will employ on-cell or in-cell integrated touch sensing.
Looking at the present state of touch technology, Synaptics is taking steps to integrate both the touch controller and display driver circuitry in a single chip, an approach Synaptics calls Touch and Display Integration or TDDI. Patrick pointed out that in-cell touch sensor designs require complex co-ordination between the touch and display functions since both share common electrodes, display noise must be managed and touch performance optimized. Worfolk cited sources of noise as display noise, charger noise, and “finger noise” that arises when the finger touching the sensor couples with noise from surrounding environmental noise sources such as fluorescent lights. Touch and display driver integration allows noise mitigation techniques such as sensing during display blanking periods, and sensing noise source frequencies and then using variable touch sensing frequencies to avoid charger and finger noise.
Worfolk pointed out that Synaptics has been investing in TDDI since 2009 as the firm acquired a display drive team from National Semiconductor in 2009, a video display operations team from Integrated Device Technology in 2012 and in 2014, acquired Renesas SP Drives, Inc. a supplier of display driver ICs for small and medium sized displays. He went on to illustrate the advantages of in-cell TDDI as shown below. Notably, the full in-cell approach results in a single TDDI chip and a single display flexible printed circuit.
Source: Synaptics
In Synaptics’ view, the in-cell TDDI approach offers both the highest performance and lowest cost and thus is the best architecture for use in future products. However, he pointed out that the complex engineering design and significant investment required for the TDDI approach necessitates a close partnership between liquid crystal module and TDDI vendors. Worfolk made the point that the market needs multiple discrete versus TDDI solutions to provide OEMs room for market differentiation. The figure below illustrates how Synaptics views the unit shipments of touch and display controller solutions currently and through 2018.
Source: Synaptics
Synaptics believes that discrete touch and display driver ICs will remain the preferred solution for premium flagship smartphones and tablets. However, two-chip in-cell and TDDI will be employed to optimize the trade-offs between performance and cost for mainstream mobile markets. Worfolk concluded his talk looking to the future where he sees TDDI laying the foundation for future features such as fingerprint sensing on glass and extending Synaptics’ offerings to newer markets, such as the automotive touch market. – Phil Wright
