The first time that I saw the Texas Instruments (TI) micromirror-based Digital Light Processor (DLP) in action was during the late 1980s when I visited the company’s headquarters in Texas. Back then, the company had incorporated DLP into a thermal ticket printer for airline ticketing. It would be another ten years before another company, Digital Projection Ltd, would introduce a video projector based on TI’s DLP technology. The following year, 1998, Digital Projection and TI would win an Emmy award from the National Academy of Television Arts & Sciences for Outstanding Achievement in Engineering Development, for the DLP projector and the associated technology as used in DLP cinema projection. Years later, in 2014, Dr. Larry Hornbeck, who invented DLP at TI back in 1987, received the Scientific and Technical Academy Award of Merit (an Oscar) for the initial invention of DMD technology.
TI says its DLPC8445DLP controller chip will enable a new generation of gaming projectors with 1 msec display latency and support for fast and variable frame rates. Image credit: Texas Instruments
Since its initial development, the cost of DLP technology has dropped, allowing DLP-based projectors to permeate many product niches including video projectors for enterprise and cinema applications, home video projectors, heads-up displays in vehicles, and even 3D printers. That evolution continues with TI’s announcement of a new, smaller DLP controller chip, the DLPC8445, which acts as a companion to its DLP472TP 4K digital micromirror device (DMD) and its DLPA3085 power management chip and LED driver.
DMDs are fascinating devices. They employ semiconductor manufacturing technology and micromachining to produce a large array of electrostatically pointable MEMS mirrors made from aluminum on the surface of a large slice of silicon. The 3840 × 2160-mirror active array on the 0.47-inch DLP472TP 4K DMD is 10.368mm wide by 5.832mm tall. (The 0.47-inch rating is the diagonal measurement of the DMD array.) The position of each mirror is controlled by one bit in a CMOS SRAM built into the DMD. Because the mirrors are either on or off, intensity control requires the use of PWM to modulate each mirror’s on and off time.
TI’s DLPC8445 DMD controller chip positions each of the DLP472TP DMD’s 8,294,400 mirrors independently so that each mirror either reflects light along the projection axis or diverts the reflected light away from the projection axis. Using a 600MHz pixel clock, the DLPC8445 DMD controller chip can project 4K video at 60Hz or 1080p video at 240Hz. The controller chip manages each mirror’s PWM timing needed for pixel-by-pixel intensity control. The controller chip also performs gamma correction to adjust intensity levels to match human perception.
The controller chip’s list price is $60 in 1000-unit quantities, and the chip measures a mere 9mm on a side, which is considerably smaller than the company’s previous generation controller chip. That earlier DMD controller measured 31mm on a side. The DLPC8445 DMD controller’s small size suggests TI’s recommended use for this chip, for a small 4K gaming projector, but also suggests additional applications such as laser TVs, heads-up displays in vehicles and aircraft, tabletop video kiosks, digital signage, and wearable devices. (TI doesn’t currently offer DMDs small enough for wearable devices, but the controller is ready when and if it does.)
TI has incorporated several new features into the DLPC8445 DMD controller – including support for high frame rates, low display latency, and support for variable refresh rates – that especially cater to the needs of gaming displays. Gaming enthusiasts are constantly seeking higher display frame rates, with 120 Hz rates now commonly found in high-end gaming displays. The image below graphically illustrates the reason that gamers want higher frame rates.
Motion blur decreases with frame rate. Image credit: Texas Instruments
According to TI, motion blur decreases with frame rate, as illustrated in the triptych image above. Media displays often operate with 60 Hz frame rates, but gamers value picture clarity, which can be important when you’re aiming at a target, so faster frame rates are better for gaming. The DLPC8445 DMD controller IC supports frame rates as fast as 240 Hz, but only for 1080p video. For 4K UHD video streams, the DLPC8445 DMD controller IC’s maximum frame rate drops to 60 Hz. The companion DLP472TP 0.47-Inch 4K UHD DMD, which measures 24.50×11.00mm. supports these same frame rates.
A 240Hz frame rate means that the images change as quickly as once every 4.2 msec. Consequently, the display controller also needs a low display latency, which is the amount of time it takes for the display controller to change the image after it receives a new frame. Previous TI DLP controllers employed a double frame buffer with a ping-pong architecture that added a 1-frame delay to the display latency.
TI’s new DLPC8445 DMD controller IC does not employ a ping-pong buffer. It has a rolling buffer that reduces display latency to less than 1 msec, which is well below the frame period at 240 Hz. I’m going to guess that the new architecture used for the DLPC8445 DMD controller IC exploits the fact that the DLP472TP 0.47-Inch 4K UHD DMD’s integrated CMOS SRAM is also a frame buffer. In fact, the DLPC8445 DMD controller IC may be taking advantage of the fact that it’s writing to an SRAM in the DMD and not a display to achieve some of the other benefits discussed above.
Gaming displays also need to support variable frame rates because the GPU will output video frames at varying rates as the computational load waxes and wanes. According to TI, if a video stream with a varying frame rate is used to drive a display with a fixed frame rate, unwanted image artifacts such as image stuttering and tearing can result. In addition, displays designed for fixed frame rates can lose video synchronization when confronted with video streams that have varying frame rates. Loss of video sync can ruin game play. TI’s DLPC8445 DMD controller architecture can accommodate variable frame rates.
Reference
Jesse Richuso, “Big-screen gaming anywhere: making portable 4K UHD, 240Hz gaming projectors a reality,” Texas Instruments, July 2024
