June 1999 PRELIMINARY ML6423* Dual S-Video Lowpass Filter with Phase and Sinx/x Equalization GENERAL DESCRIPTION FEATURES The ML6423 monolithic BiCMOS 6th-order filter provides a two-channel fixed frequency lowpass filtering for video applications. This dual phase equalized filter with sinx/x correction is designed for reconstruction filtering at the output of a Video DAC. A composite sum output eliminates the need for a third DAC. ■ 5.5 or 9.6MHz bandwidth with 6dB gain Cutoff frequencies are either 5.5MHz or 9.6MHz. Each channel incorporates a 6th-order lowpass filter, a first order allpass filter, a gain boost circuit, and a 75W coax cable driver. A control pin (RANGE) is provided to allow the inputs to swing from 0 to 1V, or 0.5 to 1.5V, by providing a 0.5V offset to the input. The 2X gain filters are powered from a single 5V supply, and can drive 1VP-P into 75W (0.5V to 1.5V), or 2VP-P into 150W (0.5V to 2.5V) with the internal coax drivers. ■ >40dB stopband rejection ■ No external components or clocks ■ ±10% frequency accuracy over maximum supply and temperature variation ■ <2% differential gain, <2° differential phase ■ <20ns group delay variation ■ 5V ±10% operation ■ Composite (sum) output ■ High sink current for AC coupled loads, ML6423-5 * This Product Is End Of Life As Of August 1, 2000 BLOCK DIAGRAM 10 7 4 13 VCCB VCCC VCC VCCA VOUTA (Y) VINA (Y) 16 LOWPASS FILTER A BUF ALLPASS FILTER SINX/X EQUALIZER 2X BUF 2kΩ 12 3.43kΩ IBIAS 2kΩ ∑ 15 RANGE 2X BUF VOUTB (CV) 8 3.43kΩ VINC (C) 1 LOWPASS FILTER C BUF ALLPASS FILTER SINX/X EQUALIZER 2X BUF 2kΩ VOUTC (C) 6 3.43kΩ IBIAS 2kΩ GND GNDA 2 14 Filter A Filter C ML6423-1 5.50MHz 5.50MHz GNDC 3 ML6423-2 9.6MHz 9.6MHz GNDB 9 ML6423-5 9.6MHz 9.6MHz 1 ML6423 PIN CONFIGURATION ML6423 16-Pin Wide SOIC (S16W) VINC 1 16 VINA GND 2 15 RANGE GNDC 3 14 GNDA VCC 4 13 VCCA NC 5 12 VOUTA VOUTC 6 11 NC VCCC 7 10 VCCB VOUTB 8 9 GNDB TOP VIEW PIN DESCRIPTION PIN NAME FUNCTION PIN NAME FUNCTION 1 VINC Signal input to filter C. Input impedance is 4kW. 10 VCCB Power supply voltage for output B. 11 NC No Connect 2 GND Power and logic ground. 12 3 GNDC Ground pin for filter C. VOUTA Output of filter A. Drive is 1VP-P into 75W (0.5V to 1.5V) or 2VP-P into 150W (0.5V to 2.5V). 4 VCC Positive supply: 4.5V to 5.5V. 13 NC No Connect VCCA Power supply voltage for filter A. 5 14 GNDA Ground pin for filter A. 6 VOUTC Output of filter C. Drive is 1VP-P into 75W (0.5V to 1.5V) or 2VP-P into 150W (0.5V to 2.5V). 15 RANGE 7 VCCC Power supply voltage for filter C. 8 VOUTB Sum of Filter A and Filter C. Drive is 1VP-P into 75W (0.5V to 1.5V) or 2VP-P into 150W (0.5V to 2.5V). Input signal range select. When RANGE is low (0), the input signal range is 0.5V to 1.5V, with an output range of 0.5V to 2.5V. When RANGE is high (1) the input signal range is 0V to 1V, while the output range is 0.5V to 2.5V. 16 9 GNDB Ground pin for output B. VINA Signal input to filter A. Input impedance is 4kW. 2 ML6423 ABSOLUTE MAXIMUM RATINGS Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. Storage Temperature .................................. –65° to 150°C Lead Temperature (Soldering 10 sec) ..................... 150°C Thermal Resistance (qJA) ..................................... 65°C/W Supply Voltage (VCC) ...................................... –0.3 to 7V GND .................................................. –0.3 to VCC +0.3V Logic Inputs ........................................ –0.3 to VCC +0.3V Input Current per Pin ............................................ ±25mA Supply Voltage ................................................. 5V ±10% Temperature Range ...................................... 0°C to 70°C OPERATING CONDITIONS ELECTRICAL CHARACTERISTICS Unless otherwise specified VCC = 5V ± 10%, RL =75W or 150W, VOUT = 2VP-P for 150W Load and VOUT = 1VP-P for 75W Load, TA = Operating Temperature Range (Notes 1, 2, 3) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 3k 4 5 kW ±2 % GENERAL RIN Input Impedance DR/RIN Input R Matching IBIAS Input Current VIN = 0.5V, RANGE = low VIN = 0.0V, RANGE = high Differential Gain Differential Phase V IN CL Input Range 45 –210 µA µA VIN = 0.8V to 1.5V at 3.58 & 4.43 MHz 1 % VIN = 0.8V to 1.5V at 3.58 & 4.43 MHz 1 deg RANGE = Low 0.5 1.5 V RANGE = High 0.0 1.0 V Peak Overshoot 2T, 0.7VP-P pulse 2.0 Crosstalk Rejection fIN = 3.58, fIN = 4.43MHz Channel to Channel Group Delay Matching (fC = 5.5MHz) fIN = 100kHz ±3 ns Channel to Channel Gain Matching fIN = 100kHz ±1.5 % Output Current RL = 0 (short circuit) 75 mA 45 dB Load Capacitance Composite Chroma/Luma delay % 35 pF fC = 5.5MHz ±15 ns fC = 9.6MHz ±8 ns 5.50MHZ FILTER Bandwidth (monotonic passband) –0.55dB (Note 4) 4.95 5.50 6.05 MHz Subcarrier Frequency Gain fIN = 3.58MHz 0.9 1.4 2.3 dB ML6423-1 fIN = 4.43MHz 1.1 1.6 2.5 dB Attenuation fIN = 10MHz 20 25 dB fIN = 50MHz 45 55 dB Output Noise Group Delay BW = 30MHz 1 180 mVRMS ns 3 ML6423 ELECTRICAL CHARACTERISTICS SYMBOL (Continued) PARAMETER CONDITIONS MIN TYP MAX UNITS 5.50MHZ FILTER (Continued) Small Signal Gain VIN = 100mVP-P at 100kHz, Filter A or C 5.5 6 6.5 dB Composite (CV) Small Signal Gain VINA, C = 100mVP-P at 100kHz 11 12 13 dB Bandwidth (monotonic passband) –2dB (Note 4) 8.6 9.6 10.6 MHz Subcarrier Frequency Gain fIN = 3.58MHz –0.1 0.4 1.1 dB ML6423-2 fIN = 4.43MHz –0.1 0.6 1.3 dB Subcarrier Frequncy Gain fIN = 3.58MHz –0.1 0.4 1.9 dB ML6423-5 fIN = 4.43MHz –0.1 0.6 1.1 dB Attenuation fIN = 17MHz 20 25 dB fIN = 85MHz 45 55 dB 9.6MHZ FILTER Output Noise BW = 30MHz 1 mVRMS 100 ns 12 13 dB Group Delay I CC Composite (CV) Small Signal Gain VINA, C = 100mVP-P at 100kHz 11 ML6423-5 Supply Current RL = 150W VIN = 0.5V (Note 5) 140 175 mA VIN = 1.5V 170 215 mA ML6423-5 VOUTA, VOUTB sink current VIN = 0.5V 8.3 11.5 mA ML6423-5 VOUTC sink current VIN = 0.5V 4.3 6.5 mA ML6423-5 Output DC Level VIN = 0.5V, Range = Low 0.5 V DIGITAL AND DC VIL Logic Input Low Range VIH Logic Input High Range IIL Logic Input Low VIN = GND IIL Logic Input High VIN = VCC ICC Supply Current RL = 150W VIN = 0.5V (Note 5) VIN = 1.5V Note 1: Limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions. Note 2: Maximum resistance on the outputs is 500W in order to improve step response. Note 3: Connect all ground pins to the ground plane via the shortest path. Note 4: The bandwidth is the –3dB frequency of the unboosted filter. This represents the attenuation that results from boosting the gain from the –3dB point at the specified frequency. Note 5: Power dissipation: PD = (ICC ´ VCC) – [3(VOUT2/RL)] 4 0.8 V VCC – 0.8 V –1 µA 1 µA 110 135 mA 140 175 mA 16 16 6 6 –4 –4 –14 –14 AMPLITUDE (dB) AMPLITUDE (dB) ML6423 –24 –34 –44 –24 –34 –44 –54 –54 –64 –64 –74 –74 –84 100K 1M 10M FREQUENCY (Hz) –84 100K 100M Figure 1a. Stop-Band Amplitude vs. Frequency (fC = 5.5MHz) 1M 10M FREQUENCY (Hz) 100M Figure 1b. Stop-Band Amplitude vs. Frequency (fC = 9.6MHz) 7.5 7.5 7.0 7.0 6.5 6.5 ML6423-2 ML6423-1 5.5 5.0 4.5 ML6422-2 5.5 5.0 4.5 4.0 4.0 3.5 3.5 3.0 3.0 2.5 100K 1M FREQUENCY (Hz) 2.5 100K 5.5MHz 10M 1M FREQUENCY (Hz) 5.5MHz 10M Figure 2a. Pass-Band Amplitude vs. Frequency (fC = 5.5MHz) Figure 2b. Pass-Band Amplitude vs. Frequency (fC = 9.6MHz) 220 130 200 125 180 120 160 115 GROUP DELAY (ns) GROUP DELAY (ns) 6.0 AMPLITUDE (dB) AMPLITUDE (dB) 6.0 140 120 100 110 105 100 80 95 60 90 40 85 20 100K 5.5MHz FREQUENCY (Hz) Figure 3a. Group Delay vs. Frequency (fC = 5.5MHz) 10MHz 80 100K 5M FREQUENCY (Hz) 9.3M 10M Figure 3b. Group Delay vs. Frequency (fC = 9.6MHz) 5 ML6423 FUNCTIONAL DESCRIPTION APPLICATION GUIDELINES The ML6423 single-chip dual video filter is intended for low cost professional and consumer video applications. Each of the two channels incorporates an input buffer amplifier, a 6th-order lowpass filter, a 1st-order allpass equalizer, sinx/x equalizer and an output 2X gain amplifier capable of driving 75W to ground. A third output (B) is the sum of the A and C inputs and have the identical output amplifier as the A and C channels. OUTPUT & INPUT CONSIDERATIONS The ML6423 can be driven by a DAC with RANGE down to 0V. When RANGE is low the input range is 0.5V to 1.5V. When the input signal range is 0V to 0.1V, RANGE should be tied high. In this case, an offset is added to the input so that the output swing is kept between 0.5V to 2.5V. The output amplifier is capable of driving up to 24mA of peak current; therefore the output voltage should not exceed 1.8V when driving 75W to ground. The dual filters have 2X gain. The circuit has 2X gain (6dB) when connected to a 150W load, and 0dB gain when driving a 75W load via a 75W series output resistor. The output may be either AC or DC coupled. For AC coupling, the –3dB point should be 5Hz or less. There must also be a DC path of £500W to ground for output biasing. The ML6423-5 provides higher sink current to better drive AC coupled loads. The input resistance is 4kW. The input may be either DC or AC coupled. (Note that each input sources 80 to 125µA of bias current). The ML6423 is designed to be directly driven by a DAC. For current output video DACs, a 75W or 150W resistor to ground may need to be added to the DAC output (filter input). SUPPLY NOISE CLAMPING +5V FB2 + 0.1µF 1nF 1µF INPUT DECOUPLING 0.1µF VINC + 100µF INPUT SIGNAL = 1VP-P 85Ω 100Ω 100Ω 100µF 1 DC BIAS VINC VINA 16 1k 2 1nF 3 0.1µF VOUTC 4 6 75Ω 0.1µF 7 1nF 8 GND GNDC VCC NC VOUTC VCCC VOUTB RANGE GNDA VCCA VOUTA NC VCCB GNDB 15 14 0.1µF 13 1nF 12 75Ω 11 10 0.1µF 9 1nF 75Ω Figure 4. ML6423 AC Coupled DC Bias Test Circuit 6 VINA 0.1µF 1kΩ 5 VOUTB 100µF + 85Ω 2.56kΩ INPUT TERMINATION RESISTOR FB1 1µF 2.56kΩ VOUTA ML6423 APPLICATION GUIDELINES (Continued) LAYOUT CONSIDERATIONS In order to obtain full performance from these dual filters, layout is very important. Good high frequency decoupling is required between each power supply and ground. Otherwise, oscillations and/or excessive crosstalk may occur. A ground plane is recommended. Each filter has its own supply and ground pins. In the test circuit, 0.1µF capacitors are connected in parallel with 1nF capacitors on all VCC pins for maximum noise rejection (Figure 4). Further noise reduction is achieved by using series ferrite beads. In typical applications, this degree of bypassing may not be necessary. Since there are two filters and a sum output driver in one package, space the signal leads away from each other as much as possible. Composite: When one or more composite signals need to be filtered, then the 5.5MHz and 9.6MHz filters permit filtering of one, two, or three composite signals. Over Sampling: While the ML6423 filters can eliminate the need for over sampling combined with digital filtering, there are times when over sampling is used. For these situations, 9.3MHz could be used in place of 5.5MHz. NTSC/PAL: A 5.5MHz cutoff frequency provides good filtering for 4.2MHz, 5.0MHz and 5.5MHz signals without the need to change filters on a production basis. Sinx/x: For digital video system with output D/A converters, there is a fall off in response with frequency due to discrete sampling. The fall off follows a sinx/x response (Figure 5a). The ML6423 filters have a complementary boost to provide a flatter overall response. The boost is designed for 13.5MHz Y/C and CV sampling and 6.75MHz U/V sampling. POWER CONSIDERATIONS The ML6423 power dissipation follows the formula: PD = (ICC VCC ) - V ! RL OUT 2 "# #$ 3 This is a measure of the amount of current the part sinks (current in – current out to the load). In a typical application (Figure 5b) the ML6423 is used as the final output device in a video processing chain. In this case, inputs to the ML6423 are supplied by DAC outputs with their associated load resistors (typically 75W or 150W). Resistance values should be adjusted to provide 1VP-P at the input of the ML6423. The ML6423 will drive 75W source termination resistors (making the total load 150W) so that no external drivers or amplifiers are required. Under worst case conditions: PD = (0.175 5.5) - 4 15. 3 "# = 8725. mW ! 75 #$ THEORETICAL SINX/X CORRECTION FOR 13.5MHz SAMPLING 2 2 The ML6423 provides several choices in filter cutoff frequencies depending on the application. S-Video: For Y/C (S-video) and Y/C + CV (Composite Video) systems the 5.5MHz or 9.6MHz filters are appropriate. In NTSC the C signal occupies the bandwidth from about 2.6MHz to about 4.6MHz, while in PAL the C signal occupies the bandwidth from about 3.4MHz to about 5.4MHz. In both cases, a 5.5MHz lowpass filter provides adequate rejection for both sampling and reconstruction. In addition, using the same filter for both Y/C and CV maintains identical signal timing without adjustments. AMPLITUDE FILTER SELECTION 0 –2 SINX/X ERROR FOR TYPICAL DAC AT 13.5MHz –4 0 1 2 3 4 5 FREQUENCY (MHz) 6 7 Figure 5a. Sinx/x Frequency Response 7 ML6423 10 IDEAL SINX/X RESPONSE 0 –3dB REFERENCE MARKER AMPLITUDE (dB) –10 A. ML6423 AMPLITUDE RESPONSE –20 B. SIGNAL DISTORTION SPECTRUM –30 C. RECONSTRUCTED SIGNAL SPECTRUM –40 –50 –60 0 5 10 15 20 25 FREQUENCY (MHz) Figure 6. ML6423 Reconstruction Performance in the Frequency Domain FILTER PERFORMANCE The reconstruction performance of a filter is based on its ability to remove the high band spectral artifacts that result from the sampling process without distorting the valid signal spectral contents within the passband. For video signals, the effect of these artifacts is a variation of the amplitude of small detail elements in the picture (such as highlights or fine pattern details) as the elements move relative to the sampling clock. The result is similar to the aliasing problem and causes a “winking” of details as they move in the picture. +5V DAC INPUTS Y DAC (CURRENT SOURCING ML6423 75Ω + C DAC (CURRENT SOURCING ANALOG OUTPUTS Y CV 75Ω C 75Ω DAC LOAD ADJUSTED FOR 1VP-P Figure 5b. Typical ML6423 Reconstruction Application 8 Figure 6 shows the problem in the frequency domain. Curve A shows the amplitude response of the ML6423 filter, while curve B shows the signal spectrum as it is distorted by the sampling process. Curve C shows the composite of the two curves which is the result of passing the sampled waveform through the ML6423. It is clear that the distortion artifacts are reduced significantly. Ultimately it is the time domain signal that is viewed on a TV monitor, so the effect of the reconstruction filter on the time domain signal is important. Figure 7 shows the sampling artifacts in the time domain. Curve A is the original signal, curve B is the result of CCIR601 sampling, and curve C is the same signal filtered through the ML6423. Again the distortions in the signal are essentially removed by the filter. In an effort to measure the time domain effectiveness of a reconstruction filter, Figure 8 was generated from a swept frequency waveform. Curves A, B, and C are generated as in Figure 7, but additional curves D and E help quantify the effect of filtering in the time domain. Curves D and E represent the envelopes (instantaneous amplitudes) of curves B and C. Again, it is evident in curve D that the envelope varies significantly due to the sampling process. In curve E, filtering with the ML6423 removes these artifacts and generates an analog output signal that rivals the oversampled (and more ideal) signal waveforms. The ML6423 reduces the amplitude variation from over 6% to less than 1%. ML6423 A. OVERSAMPLED WAVEFORMS B. CCIR601 SAMPLED WAVEFORMS C. ML6423 RECONSTRUCTED WAVEFORMS Figure 7. ML6423 Reconstruction Performance in the Time Domain A. OVERSAMPLED SIGNAL B. CCIR601 SAMPLED SIGNAL C. ML6423 FILTERED SIGNAL D. CCIR601 SAMPLED WAVEFORM >6% E. ML6423 FILTERED WAVEFORM <1% Figure 8. Amplitude Ripple of Reconstructed Swept Pulses 9 ML6423 PHYSICAL DIMENSIONS inches (millimeters) Package: S16W 16-Pin Wide SOIC 0.400 - 0.414 (10.16 - 10.52) 16 0.291 - 0.301 0.398 - 0.412 (7.39 - 7.65) (10.11 - 10.47) PIN 1 ID 1 0.024 - 0.034 (0.61 - 0.86) (4 PLACES) 0.050 BSC (1.27 BSC) 0.095 - 0.107 (2.41 - 2.72) 0º - 8º 0.090 - 0.094 (2.28 - 2.39) 0.012 - 0.020 (0.30 - 0.51) SEATING PLANE 0.005 - 0.013 (0.13 - 0.33) 0.022 - 0.042 (0.56 - 1.07) 0.009 - 0.013 (0.22 - 0.33) ORDERING INFORMATION PART NUMBER BW (MHZ) TEMPERATURE RANGE PACKAGE ML6423CS-1 (EOL) ML6423CS-2 (EOL) ML6423CS-5 (Obsolete) 5.5/5.5 9.6/9.6 9.6/9.6 0°C to 70°C 0°C to 70°C 0°C to 70°C 16-pin Wide SOIC (S16W) 16-pin Wide SOIC (S16W) 16-pin Wide SOIC (S16W) © Micro Linear 2000. property of their respective owners. is a registered trademark of Micro Linear Corporation. All other trademarks are the Products described herein may be covered by one or more of the following U.S. patents: 4,897,611; 4,964,026; 5,027,116; 5,281,862; 5,283,483; 5,418,502; 5,508,570; 5,510,727; 5,523,940; 5,546,017; 5,559,470; 5,565,761; 5,592,128; 5,594,376; 5,652,479; 5,661,427; 5,663,874; 5,672,959; 5,689,167; 5,714,897; 5,717,798; 5,742,151; 5,747,977; 5,754,012; 5,757,174; 5,767,653; 5,777,514; 5,793,168; 5,798,635; 5,804,950; 5,808,455; 5,811,999; 5,818,207; 5,818,669; 5,825,165; 5,825,223; 5,838,723; 5.844,378; 5,844,941. Japan: 2,598,946; 2,619,299; 2,704,176; 2,821,714. Other patents are pending. Micro Linear makes no representations or warranties with respect to the accuracy, utility, or completeness of the contents of this publication and reserves the right to make changes to specifications and product descriptions at any time without notice. No license, express or implied, by estoppel or otherwise, to any patents or other intellectual property rights is granted by this document. The circuits contained in this document are offered as possible applications only. Particular uses or applications may invalidate some of the specifications and/or product descriptions contained herein. The customer is urged to perform its own engineering review before deciding on a particular application. Micro Linear assumes no liability whatsoever, and disclaims any express or implied warranty, relating to sale and/or use of Micro Linear products including liability or warranties relating to merchantability, fitness for a particular purpose, or infringement of any intellectual property right. Micro Linear products are not designed for use in medical, life saving, or life sustaining applications. 2092 Concourse Drive San Jose, CA 95131 Tel: 408/433-5200 Fax: 408/432-0295 www.microlinear.com 10 DS6423-01