[Technology Report]
Digital TV, Audio Boost Analog/Mixed-Signal
Innovation in the analog domain has never been stronger thanks to a series of new applications from the digital side.
It's next to impossible to encapsulate the concept of "high-performance" analog in a few simple datasheet specs like bandwidth or conversion rate or resolution. Dimensions of performance, to borrow a term from Analog Devices, expand and contract according to the application, and they include less obvious factors like power consumption, package size, and even price.
FOLLOWING THE APPS One way to sort out performance issues is to sort new analog products by application area to see where they cluster and what specs are emphasized. If you do that, innovation and competition are clearly strongest in the multimedia market. In fact, many new analog products don't fit the traditional amplifier/data converter categories.
There are new competitors as well. Fairchild Semiconductor now has its own Korean fab and is making monolithic amplifiers for digital video. Cirrus Logic continues to redefine itself as a performance leader in high-end audio and digital TV. Meanwhile, the established analog players, including ADI, National Semiconductor, Linear, Intersil, Maxim, and Texas Instruments, continue to innovate.
VIDEO Let's start with a look at new products for video that are destined for OEM products from cell phones to HDTV receivers. Fairchild Semiconductor's 210-MHz FHP3x50 family (triples and quads) and 50-MHz FHP3x30 family (single, dual, and quad) target high-definition (HD) and standard-definition (SD) video applications, respectively (Fig. 1).
The HD devices exhibit 210-MHz, −3-dB bandwidth, and 1100-V/µs slew rates, along with 0.07%/0.03° differential gain and phase errors. Their 0.1-dB gain flatness extends to 50 MHz. Both consume 3.6 mA of supply current per amplifier. Additionally, a ±55-mA output current rating supports multiple video loads.
The SD family is characterized by 16-MHz, 0.1-dB gain flatness, greater than 100-dB open loop gain, power-supply rejection ratio (PSRR), and common-mode rejection ratios (CMRRs). They draw 2.5-mA supply current per amplifier while providing ±100-mA output capability—enough to support four video loads. Thousand-piece unit pricing is $0.71 and $0.83 for the triple and quad HD parts and from $0.63 to $0.86 on the SD parts, depending on the number of amps and package type.
The LT6557 single-supply, triple video amplifier from Linear Technology fits high-resolution LCD projectors and monitors as well as automotive display systems (Fig. 2). Its input swing extends to 0.8 V of the rails, enabling it to amplify a full video signal when operating from one 5-V supply. Its 23-dB bandwidth is 500 MHz, slew rate is 2200 V/µs, and settling time is 4 ns. And, its 0.1-dB gain flatness extends to 120 MHz.
An internal biasing feature lets circuit designers program the inputs of all three amplifiers to the same dc voltage level with a single resistor. Pricing starts at $2.50 each in 1000-piece quantities.
Also for applications in projectors and monitors, National Semiconductor's LMH6582 (gain = 1) and LMH6583 (gain = 2) 16-by-8 analog crosspoint switches also achieve a 500-MHz, −3-dB bandwidth, with 0.1-dB gain flatness out to 100 MHz and slew rates up to 3000 V/µs. Channel-to-channel crosstalk is −50 dBc at 100 MHz. Each buffered output can drive up to two back-terminated, 75-Ω ½ video loads.
One of the really clever features of the chips is their pin arrangement Essentially, diagonal symmetry in pin assignments makes it easy to use direct pin-to-pin vias when the parts are mounted on opposite sides of a board. As a result, a pair of chips forms either a 16-by-16 crosspoint or a 32-by-8 crosspoint. Both devices cost $39.95 in 100-unit quantities.
National also introduced a low-jitter sync separator IC for high-definition video formats that eliminates the need for extra filtering and jitter-cleaning stages. The LMH1981 accepts video signals from composite (CVBS), S-video (Y/C), component (YPbPr), and computer interfaces, providing horizontal, vertical, and composite sync, odd/even field, and burst/back porch clamping.
It accepts both bi-and tri-level sync video inputs. Proper, 50% slicing ensures accurate separation of signals that vary in amplitude, offset, and noise. Based on National's inputreferred jitter testing of high-definition video inputs, horizontal-sync jitter can be as much as 30% lower than approaches that use multiple stages or FPGAs after sync separation to clean and filter jitter.
Automatic video-format detection can be used to inform the downstream video system of format changes so the system can dynamically adjust system parameters, such as color space or scalar conversions. An output pin on the chip outputs the total vertical resolution or line count through an 11-bit binary data stream.
The LMH1981 operates on single-supply voltages between 3.3 and 5 V. It's compatible with the Macrovision Video Copy Protection System commonly used in VHS and DVD video sources. Sampling now, the LMH1981 will cost $3.79 in 1000-unit lots.
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