feature

7.6MHz fifth-order RGB/YUV/YC Cv filter 50dB stop-band attenuation on all outputs at 27MHz Better than 0.5dB flatness on all outputs up to 4.2MHz No external frequency selection components or clocks AC-coupled input and AC or DC-coupled Output supports NTSC and PAL luma bandwidth Continuous-time low-pass filter for video anti-aliasing or reconstruction applications <1% differential gain, 0.5° differential phase on all channels Low tilt

application

Cable STB Satellite STB Terrestrial STB DVD Player Personal Video Recorder (PVR) Video On Demand (VOD)

illustrate

The FMS6408 provides three video signal paths; including dual input mux, video filter and 6db gain output driver. The filter bandwidth supports rgb and YUV signals in NTSC or PAL format. The video filter approximates the 5th order Butterworth minimum optimized low-pass characteristic overshoot and flat group delay to provide excellent image quality. Four different peaking options are available. Video filters can be bypassed if desired. In a typical application, the rgb or yuv dac output is AC coupled into the filter through the input multiplexer. All channels have DC restoration circuitry to clamp the input level during DC video sync. The resulting clamp pulse feeds back the clamp from the selected Y input control. All outputs can drive 2VPP, AC or DC coupled, for single ( 150Ω ) or dual (75Ω) video loading. The FMS6408 clamp levels can be factory programmed for YUV/RGB (all 250 mV channels), YC/YPBPR (1.125V on channels 1 and 2 and 3, or YC Cv (250 mV on channels 1 and 3 and on channel 2) 1.125V).

Function description introduction: This product is a three-channel monolithic continuous temporal video filter used to reconstruct yuv, yc cv or rgb signal from video d/a source. The input should be AC coupled, while the output can be AC or DC coupled. The reconstruction filter approximates the A5 order Butterworth response, optimized for minimum overshoot and flat group delay. This provides delay and maximum flat response amplitude. Each of the three outputs is capable of driving 2vpp into a 75Ω load. All channels are clamped during the sync interval to set the proper DC output level. Synchronous tip clamping greatly reduces the effective input time constant, allowing the use of small, low-cost input coupling capacitors. There is a dc shift in a typical video signal. In most applications, the input coupling capacitor is 0.1µF. The input is usually in the active video. For the yuv signal, this translates to 2mv sloping along the horizontal line at the Y output. During synchronization, the clamp passes an average of 20 µA from the clamp interval. Any change in coupling capacitor value affects the amount of tilt per line. Any reduction in tilt comes with resolution time. The input input is typically driven by a low impedance source of 1vpp or a termination line of 75Ω driven by the output of the current dac. In either case, the input must be capacitively coupled to allow the synchronization detection and DC restoration circuits to operate properly. Outputs The outputs are low impedance voltage drivers that can handle single or dual loads. One load consists of a 75Ω series terminating resistor to form a 75Ω-150Ω partial total load termination line. Even in the presence of two loads (75Ω), the driver produces a full 2vpp signal on its output pins. Drivers are also available to drive AC-coupled single or dual loads. When driving dual loads, if the other output connection is accidentally shorted, if those loads are AC coupled.

Application note introduction: FMS6408 can drive dual 75Ω loads, where the load consists of a 75Ω resistor and a 75Ω resistor in series to form a terminating resistor in the drive device. This one shows a 150Ω load to the output, so the two are similar from the output to ground. In some cases, driving a single load on one or more outputs and a double load on the remaining outputs. This is an acceptable loading condition, but may result in slightly degraded gain matching. Device Power Consumption The FMS6408 specification provides a quiescent no-load supply current of 52MA (typ). With a nominal 5V supply, this results in 260 megawatts. The overall power dissipation can be significantly affected by the applied load, especially in DC coupled applications. Calculate the total power dissipation typical of the output voltage and must know the loading conditions. The power dissipation of YUV video is highest coupled to the DC signal in the dual video load (see diagram). Assuming that there is a video signal on the Y channel with an average brightness of 50%, the output voltage is

1.55V, then calculate the load current: Set the average DC level of the U and V channels to 1.125V through the clamp circuit. signal is

Symmetrical to this voltage, so: Equipment losses due to this load are internal

Voltage drop times load current: Because the power dissipation of u and v is approximately the same due to

Load can be estimated by: This brings the typical total equipment power dissipation to 260mw (static power) + 187.55MW (load power) or 447.55MW . It is recommended to calculate the quiescent power consumption current and the maximum allowable power supply voltage for the maximum possible power bad case. When calculating the mold temperature rise provides θja, the thermal resistance value. Field Time Distortion In AC-coupled output applications, the coupling capacitor controls the field time distortion. Use 220µf coupling specified performance capacitors; if better performance is required, add capacitors or output DC coupling.