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Single and Dual Video Line Drivers with Integrated Filters Replace Discrete Components to Save Board Space, Reduce Cost
| The manufacturer says . . . | ChipCenter's Paul O'Shea says . . . |
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Fairchild Semiconductor International introduces the FMS6413 (single channel) and the FMS6414 (dual channel) video line drivers with integrated video low pass filters for standard definition composite and S-video applications. These monolithic devices combine 75 ohm cable drivers with integrated filters, allowing them to remove artifacts introduced during D/A conversion in the encoder. These low-cost, space-saving devices replace discrete filters and line drivers in CCTV, set top box, DVD player, video camera and television applications. The FMS6413 is a single channel filter-driver. It features 1.0dB flatness across the pass band, a 7.1 MHz cutoff frequency, and 37 dB stop-band rejection at 27 MHz. The filter approximates the performance of a 4th order Butterworth filter with an optimization toward low overshoot and flat group delay. The driver is capable of driving 2Vp-p into a 150 ohm load and offers less than 0.4% differential gain and 0.4% differential phase for the video signal. The FMS6413 is ideally suited for composite video applications where only a single video signal is involved. This monolithic device includes DC restore/sync-tip clamp circuitry for proper operation. The FMS6414 is a dual channel filter-driver. It has the same filter characteristics as the single filter FMS6413, but adds the flexibility of a second channel that is generally used for the Chroma signal. The FMS6414 is perfectly suited for S-Video and other similar applications where the chrominance (chroma) and luminance (luma) are separated. Both the FMS6413 and the FMS6414 are offered in a space- and cost-saving 8-pin SOIC package. Price: FMS6413 is U.S. $0.79 and the FMS6414 is U.S. $0.91 (1,000 pcs.) Availability: Now Delivery: 4 weeks ARO For more information, contact Fairchild Semiconductor's Customer Support Center at 888-522-5372, Fax 972-910-8036, or visit Fairchild's website at www.fairchildsemi.com |
The real value in these line driver products is in the video driver. The filter is important, but in terms of the cost component of the chip ę the real value is added in the video driver. This introduction rounds out a family of line driver parts from Fairchild Semiconductor. Spec and performance wise the two filters, the FMS6413 and 6414, are intended for the exact same purpose with one difference ę the 6413 has a single path and the 6414 has a dual path. They are intended for the designer that doesnęt want/need a three channel driver and for those that need a single channel. They also compete pretty much head to head with similar parts from Maxim. Fairchild says that their line drivers are easier to use and donęt require a busing sequence to set up their filters. These video drivers from Fairchild have integrated low-pass filters and have a DC restore circuit. It is useful for an input circuit because it has a DC restore clamp, so it can be used by someone needing to DC restore their video. For example, with DC restore you may not be sure at what DC level your video comes in, so you need to AC couple the signal at the input, put a capacitor in the path, then clamp on the sync tip, which is the lowest level video to a DC level that the chip can use. Thatęs useful especially for a TV set because you donęt know what the video level be will since it comes from a random source. The line drivers can be used in set top boxes (STBs) and placed after a digital-to-analog converter for reconstruction of the signal. It allows the user to drive a 75 ohm video cable directly between the STB and TV set. Fairchild says they are also targeting digital still cameras, closed circuit TVs, DVDs, and personal video recorders. Additionally, when you perform a digital-to-analog conversion you get some quantization artifacts. When a signal comes out of an 8-bit D-to-A converter you typically see some high frequency artifacts or noise. The filter component of the chip blocks or filters out that noise. The Fairchild design uses that pass filter to get rid of anything above 7.1 MHz. The 7.1 MHz cut off frequency allows enough bandwidth for a typical NTSC or PAL video signal. There are other cutoffs that could be used but 7.1 MHz works well for a composite signal. If you are only looking for a composite out then you need only the single channel FMS6413. Fairchild thinks that the single channel version will be more popular than the dual channel FMS6414. The dual channel is appropriate for S-video applications. Your purchasing department will also like these components because both parts use the same footprint, which means you can just drop-in the appropriate part without any redesign. That way you keep your inventory in check and get a better economy of scale for volume pricing. |
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