The Panasonic PT-50LCX63 is a 50-inch digital high-definition television (HDTV) direct-view projection system loaded with picture-in-picture (PIP), split-screen, and an array of audio, video, and memory card inputs. While our full analysis extends to the much more complex total system, this column's focus is on the critical role of analog technology in getting your favorite programming onto the big screen.
Three high-resolution LCD panels"one for each of the red, green, and blue primary colors"generate the final picture. A high-intensity lamp is collimated, split, and color-filtered to pass through each of the LCDs which act as light valves for modulating the desired on-screen image. A series of complex prisms and lenses recombines the output of the LCD panels and projects them via a reflecting mirror onto the large front screen panel, itself a trick piece of optics engineering.
Driving the LCD panels remains the key piece of analog artistry. Supplying information to refresh the high-resolution picture around 30 times per second while accommodating 16.7 million colors means a whole lot of data. Back on the main system board"not shown"a National Semiconductor Low Voltage Differential Signaling (LVDS) driver (#DS90C385MTD) sends serialized RGB data to the LCD driver board at a blazing 1.4Gbits/sec. While LVDS is a digital transmission, mixed-signal finesse is needed to reliably transmit the high-speed bit stream, in essence a wideband analog signal-integrity challenge.
Once data arrives on the LCD board, a National Semiconductor LVDS Receiver (#DS90CF386NTD) recreates a 24-bit parallel data stream for delivery to a Kawasaki ASIC. The Kawasaki chip (#E07050K0B) shuttles data to a set of 10-bit high voltage D-A converters from Analog Devices (#AD8383) which directly interface to the LCD panels as shown with the red arrows. With such a huge color palette, precise control of the analog signal levels driving the LCDs is critical to keep hues, brightness, and uniformity all up to spec.
At $2500 or more the Panasonic isn't cheap, but in the end this digital TV relies on analog technology to get the picture to the finish line and serve up a beautiful viewing experience.
David Carey is President of Portelligent. The Austin, Texas company produces teardown reports and related industry research on Wireless, Mobile, and Personal Electronics. (www.teardown.com)