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Video filter/driver eliminates dozens of discrete devices

Posted: 08 Sep 2005 ?? ?Print Version ?Bookmark and Share


Fairchild Semiconductor's FMS6406 is the industry's most highly integrated standard definition, low-pass reconstruction video filter/driver. This device features an integrated sound notch and output drivers that meet the latest cable and satellite set-top box performance requirements of 170ns group delay predistortion.

The FMS6406 compensates for the inherent distortion in the TV receiver by including a group delay and chroma-luma delay FCC predistortion circuit that prevents the image's high-frequency edges from appearing distorted on the TV screen. The notch filter creates a window in the video signal at approximately 4.5MHz to eliminate interference between the audio and video before these signals are combined in the channel 3/4 RF modulator.

"Fairchild's highly integrated video filter reduces board space by 30 to 40 percent by effectively replacing discrete reconstruction filters, an external sound notch and group delay compensation circuits and cable drivers, while increasing system reliability in set-top box and personal video recorder (PVR) applications. This integration translates into significant board savings," says Jeremy Tole, Fairchild's technical marketing manager for video products. "The FMS6406 answers a pressing need in the STB and PVR market by providing a highly efficient and inherently low-cost system solution."

Fairchild's FMS6406, a 5th order video filter, eliminates unwanted digital artifacts by significantly reducing the clock and image frequencies after the digital-to-analog conversion process occurs on an MPEG chip. This video filter/driver is also capable of DC coupling on the outputs to improve the low-frequency video, while at the same time eliminating the need for three large capacitors.

Typical designs for set-top boxes offer both S-video and composite-video outputs. Fairchild's FMS6406 offers separate chrominance and luminance outputs to directly drive the S-video output. These outputs are also internally summed to form a composite video signal. The composite- and S-video outputs provide a fixed gain of 6dB and offer the flexibility of either AC or DC coupling.

Key features include:

? dual 5th order 7.6MHz low-pass filters eliminate unwanted digital artifacts;

? integrated equalizer and sound notch filter for driving the RF modulator;

? 4.5MHz sound trap removes video noise in the spectral location of the subsequent FM audio carrier;

? 170ns group delay/chroma-luma delay predistortion for NTSC applications (as required for broadcast transmitters by the FCC) compensates for the inherent receiver IF filter's group delay distortion;

? AC-coupled inputs and a DC restoration circuit for low tilt;

? the inputs are Y/C and include a Y sync tip clamp and chroma blanking clamp;

? the filtered outputs are Y/C and CV with 50dB stopband attenuation at 27MHz and better than 0.5dB flatness to 4.2MHz;

? all outputs are capable of driving 2Vpp, AC- or DC-coupled, into either a single or dual 75-ohm video load; and

? internal chroma-luma summing circuit for driving composite video outputs.

The FMS6406 is offered in an 8-pin SOIC package. This product is Pb-free and meets or exceeds the requirements of the joint IPC/JEDEC standard J-STD-020B and is compliant with European Union requirements now in effect.

Already available, the FMS6406CS (rail) and FMS6406CSX (tape reel) are priced at $1.69 each in 1,000-piece quantities. Delivery is 12 to 16 weeks ARO.

- Janine Love


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