audio/videoZONE Products for the week of September 22, 2003
Fairchild Semiconductor Says . . .
FMS6417: Video Filter/Line Driver Offers Integrated
Solution For STB/DVDs
Fairchild Semiconductor announced the FMS6417, a comprehensive video filtering and line driving solution that offers more functionality than competitive parts. The FMS6417 is a five-channel, video reconstruction filter that includes selectable RGB (YUV) high definition and standard definition (HD/SD) filters with Y, C, composite, and modulator outputs. This integrated product combines video line drivers, sound notch, and multiple video input/output standards--all in one chip. The FMS6417 is ideal for applications such as cable and satellite set top boxes, DVD players, PVRs (Personal Video Recorders ), HDTVs, VODs (Video on Demand ) and TVs.
With its ability to remove high frequency noise prior to digitizing the signal (anti-aliasing) or to remove artifacts introduced during D/A conversion in the encoder (reconstruction), this monolithic device can be used for anti-aliasing or reconstructive (smoothing) filtering for RGB, component, S-video, and composite video signals.
The FMS6417 consists of a triple 6th order filter with selectable 30MHz and 8.0MHz frequencies and a dual 8.0MHz filter for filtering Y/C. The filter contains a summing circuit to generate filtered composite video, an audio trap, and group delay compensation circuits to notch-out audio and group delay predistortion for NTSC. In addition, 2-to-1 multiplexers are provided on the triple filters, as well as provisions for auxiliary inputs to the composite channel. The FMS6417 also includes DC-coupled inputs and all outputs can drive AC-coupled, 75O loads and provide 6dB of gain.
"The FMS6417 is a fully-integrated part that allows the customer
to reduce overall component cost and parts-count for their video output
requirements," said Jeremy Tole, Fairchild's technical marketing manager
for video products. "The FMS6417 is the first in a line of comprehensive
HDTV-related products, which will help enable the proliferation of HDTV
products in the marketplace."
analogZONE Says...
This is a fairly complete filter solution that will help enormously in the cross-over products between standards which are going to be frequently encountered over the next few years. And from the technologies that Fairchild has acquired I have no doubt that the specifications it provides are accurate. But the company lets itself down in definitions and raises question marks about meanings.
The data sheet and press release both suggest that the GBR channels (we have been using GBR instead of RGB in the video world for a long time) can be driven by YUV signals. U and V are the weighted color-difference signals in PAL modulation, so obviously the company means something else; a lot of people from the computer world misuse YUV instead of SMPTE Y, Pb, Pr color-difference signals. But that cannot be the case here because how could the part operate on color-difference signals when the rail is a single +3.3 V with signals related to ground?
We also have differential phase and gain measured for G, B, R, Y and C channels. Why? And SNR in SD mode is quoted as -60 dB (the minus sign is interesting just by itself) with "100 kHz highpass enabled." What 100 kHz highpass, and why? And in the HD specifications the SNR is quoted at -65 dB (that darned minus sign again) with "NTC-7 weighting 4.2 MHz lowpass." In 20-MHz channels -- why?
All the channels are set up for ac coupled inputs and outputs with a 2:1 MUX on the GBR channels to switch between A and B channel inputs (all three switch together.) There is a separate MUX on the Y and C input channels which inputs those two signals or just an auxiliary feed on the Y MUX. The GBR filters are all switchable (together) from a 5 MHz (-1 dB) filter for SD to a 20 MHz (-1 dB) filter for HD. The overall channel gains are 6 dB allowing the part to drive a double-terminated coaxial line. Delays through the GBR channels are 65 ns in SD and 20 dB (!), presumably a typo for ns, in HD, both measured at 4.5 MHz. The group delays are both typically -170 ns from 400 kHz out to 3.58 MHz and 30 MHz for the respective standards. Flatness in the GBR channels is within ±0.75 dB for SD, and is not quoted for HD -- although it is unlikely to be much different.
The filters in the YC (or AUX) channels are similar to the others (there is no indication that a bandpass filter is used for C) and they are non-switchable to a higher bandwidth, for which there would be no need. Apart from the direct outputs there is also an adder to provide a raw composite signal and a further channel with a modulator to predistort group delay and provide audio notching.
The part is specified with a 3.3 V rail and a 5.0 V output/modulator rail. Total power is a typical 133 mW. PSRR on all channels is 46 dB while GBR channel-to-channel crosstalk is worst case (SD) a typical -65 dB
In spite of the unnecessary confusions, this part will find a lot of sockets in PVRs, STBs, DVD players and recorders where the HD switching will allow multiple use with considerable simplicity. The specifications are well suited for high-end consumer equipment. Some products will inevitably have to add additional switching at the inputs using other parts, but Fairchild has a large selection of analog switches to help that choice along.
The FMS6417 is in production in a LQFP-32 and is priced at $2.70 in 1000-piece lots. A demo board is available.