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| GT4122 Video Multiplier DATA SHEET FEATURES * broadcast quality video multiplier * 30 MHz at -1.0 dB video and control channel bandwidth * one external frequency compensation adjustment * ultra low differential gain and differential phase, (typically 0.01 % and 0.01 deg.) * external DC offset and span trims * 20 pin PDIP and SOIC packaging APPLICATIONS * Production switcher video mixers * Linear Keyers PIN CONNECTIONS TOP VIEW TOP VIEW -VS +VS COMP COS1 COS2 S1 VREF S2 VC GND 10 11 PIN 1 20 OUT BOS2 -IN B +IN B BOS1 AOS2 -IN A +IN A AOS1 REXT DESCRIPTION The GT4122 multiplier is a monolithic dual-channel, broadcast quality video mixer. Featuring two wideband video inputs and a single control input, the GT4122 achieves high quality video mixing of the two video input signals to a single output by implementing the function: V OUT = V A * VC + V B (1 - V C) where VC is the control input voltage, which may be varied continuously over the control range and VA and VB are the video input signals. The GT4122 operates with power supply voltages of 10 volts and typically draws 24 mA of current. The GT4122 is available in a 20 pin DIP and 20 pin SOIC packaging. An Application Note entitled `Using the GT4122 and GT4124 Video Mixer ICs' (Gennum Document 520-44) is available from Gennum Corporation. ORDERING INFORMATION Part No. GT4122 - CDF GT4122 - CKF Package Type 20 PDIP 20 SOIC Temperature 0 to 70C 0 to 70C 20 PIN DIP / SOIC +IN A - IN A A OS1 A OS2 + AMP 1 PIN DESIGNATION 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 -VS negative supply voltage +V S positive supply voltage COMPoutput freq'y comp'n R-C COS1 control input offset adjust COS2 control input offset adjust S1 span adjust VREF 0.5volt reference input S2 span adjust VC control signal input GND ground REXT current setting resistor AOS1 A black level adjust (OFFSET) +IN A A video + input signal -IN A A video - signal input AOS2 A black level adjust (OFFSET) BOS1 B black level adjust (OFFSET) +IN B B video + signal input -IN B B video - signal input BOS2 B black level adjust (OFFSET) OUT multiplier output XA VCA=0.5 + VK COMP + 1 AMP 4 OUT + + AMP 2 +IN B - IN B B OS1 REXT XB BIAS + VCB=0.5 - VK - VK 2 + 3 AMP 3 + VK VNOM AK + B OS2 VREF VC S1 S2 COS2 COS1 - VS VNOM + + 0.5V + +VS GND - - Device Function: V OUT = V INA * [VNOM + AK (V C - VREF)] + VINB * [VNOM - AK (VC - VREF)] FUNCTIONAL BLOCK DIAGRAM Document No. 520 - 25 - 4 Revision Date: January 1994. GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-5946 Japan Branch: A-302, Miyamae Village, 2-10-42 Miyamae, Suginami-ku, Tokyo 168, Japan tel. (03) 3334-7700 fax: (03) 3247-8839 ABSOLUTE MAXIMUM RATINGS PARAMETER Supply Voltage (VS) Operating Temperature Range Storage Temperature Range VALUE 13.5 V 0 C TA 70 C -65 C TS 150 C 260 C 5 V 5 V 5 V 5 V Lead Temperature (Soldering, 10 Sec) Video Input Voltage (VA,V B) to ground Control Input Voltage (VC) to ground Video Input Differential Voltage (VA - VB ) Control Input Differential Voltage (VC -VREF) ELECTRICAL CHARACTERISTICS (+VS = -V S =10V, 0C TA 70C unless otherwise shown) PARAMETER Supply Voltage POWER SUPPLIES SYMBOL VS I+ IBW CONDITIONS Operating Range R EXT = 1 k REXT = 1 k at 0.1 dB V SIG =150 mVp-p DC - 10 MHz MIN 9 25 64 54 -0.01 - TYP 10 24 18 30 0.05 0.01 0.01 70 60 -0.005 85 95 30 1 -55 3 - MAX 12 28 20 0.03 0.03 66 10 10 -50 5 +5 UNITS volts mA mA MHz dB % degrees dB dB dB ns dB dB MHz ns % dB mVpp V + Supply Current - Supply Current Bandwidth Frequency Response Differential Gain Differential Phase g p S/N AOL ACL td SIG VA or B/VO VC /VA or B V IN = 40 IRE at 3.58 MHz V IN = 40 IRE at 3.58 MHz V SIG = 1 volt, BW = 5 MHz 100 kHz ( = 0%) 100 kHz ( = 100%) SIGNAL CHANNEL Signal to Noise Gain - open loop Gain - closed loop Delay Off Isolation & Crosstalk SIG = 5 MHz (see note 1) SIG = 5 MHz (see note 2) at 0.1 dB V SIG =150 mVp-p 80 90 25 - Bandwidth Delay CONTROL CHANNEL BW t d CONT Linearity Control Breakthrough Crossfade Balance Control Range V CONT VCONT = 0-1 V = 1-10 MHz V CONT = 0-1 V = 3.58 MHz 0 NOTE: 1 VA or B =1 Vp-p output taken from OUTPUT 2 VCONT =1 Vp-p output taken from VA or VB 520 - 25 - 4 2 DETAILED DESCRIPTION The GT4122 is a broadcast quality monolithic integrated circuit specifically designed to linearly mix two video signals under the control of a third signal. Referring to the block diagram, the input signals are applied to conventional differential amplifiers (AMP1 and AMP2). Each amplifier has provisions for individually adjusting the DC offset (OFFSET). Following each input amplifier, the signals are applied to linear multiplier circuits (XA and XB) whose outputs are the product of the incoming signals and controlling voltages (VCA) or (VCB ). The controlling voltage VCA is the sum of a nominal 0.5V source (VNOM ) and a variable source VK while VCB is made up of the sum of the nominal voltage VNOM and -VK. VK and -VK are themselves proportional to the difference between an externally applied reference voltage (VREF) and an externally applied CONTROL voltage (VC). The voltages VK and -VK are produced by a differential amplifier (AMP3) whose gain is AK. This gain can be altered by two external resistors, REXT and RSPAN according to the following formula: 0.85 * REXT AK ---------- RSPAN [1k < REXT < 3k] When they are exactly 0.5V and when VC = V REF, the gain of each signal channel of the mixer is 0.5 (50%). By connecting the ends of an external potentiometer (CONTROL OFFSET) between the offset pins COS1 and COS2, the voltage sources can be altered differentially. If a second potentiometer (50% GAIN) is connected between the wiper of the CONTROL OFFSET potentiometer and the supply voltage, the voltage sources can be varied in a common mode fashion. In this way not only can the control range of the mixer be varied but also the point at which 50% of each input signal appears at the output. The outputs from the multiplier circuits (XA and XB) are then applied to a summing circuit (1) whose output feeds a wideband amplifier (AMP4) and presents the mixed signals to the outside world. Although there are two separate differential inputs, the usual operational amplifier gain-setting methods can be applied to determine the closed loop gain of the mixer. Usually the mixer will be configured for unity gain by connecting both inverting inputs (-IN A , -IN B) to the common output (OUT). In this case, the general transfer function is: VO = VA *[VNOM + AK*(VC - VREF)] + VB*[VNOM - AK*(VC VREF)] (Unity gain configuration) Where VA and VB are the input analog signals applied to +IN A and +IN B respectively, and VC is the CONTROL voltage. Note that VNOM ranges between 0.45V < VNOM < 0.55. Note that REXT is connected between the REXT pin and ground and RSPAN is connected between the pins S1 and S2. Each of the voltages (+VK and -VK) is applied to summing circuits (2 and 3) whose second inputs are DC voltage sources that can also be slightly varied. The nominal value of these voltage sources is 0.5 volts. +IN A - IN A A OS1 A OS2 + AMP 1 XA VCA=0.5 + VK COMP + 1 AMP 4 OUT + + AMP 2 +IN B - IN B B OS1 REXT XB BIAS + VCB=0.5 - VK - VK 2 + 3 AMP 3 + VK VNOM AK + B OS2 VREF VC S1 S2 COS2 COS1 - VS VNOM + + 0.5V + +VS GND - - Device Function: VOUT = VINA * [VNOM + AK (VC - VREF)] + VINB * [VNOM - AK (VC - VREF)] FUNCTIONAL BLOCK DIAGRAM 3 520 - 25 - 4 For normal video mixer operation, the control range (SPAN) is usually 0 to 1V and will occur when AK=1, VREF= 0.5V and VNOM=0.5 volts. A change in VC from 0 to 1V will then produce an effect such that the output signal contains 100% of Channel B when VC is 0V and 100% of Channel A when VC is 1 volt. For the above conditions, the general unity gain transfer function reduces to: VO = VA*VC + VB*(1-VC) Since the operation of the mixer is limited to two quadrants, no signal inversions occur if the control voltage exceeds the range zero to one volt in either direction. The topology is designed so that once the control voltage reaches either end of its range, the channel which is ON remains fully ON and the OFF channel remains fully OFF. +10V C5 47 -10V +5V GT4122 1 -V S 2 +VS 3 COMP 4C OS1 5C OS2 6 S1 7 1K 8 9 VREF S2 VC GND OUT B OS2 -IN B +IN B B OS1 A OS2 -IN A +IN A AOS1 REXT 12 11 R2 1k 75 if required CONTROL INPUT 75 if required 20 19 18 17 16 15 14 13 RV5 500 A BLACK LEVEL ADJUST 75 if required A VIDEO INPUT RV4 500 IC2 CLC110 4 ROUT 10k or OPEN 5 1 8 VIDEO OUT C7 0.1 C6 0.1 C5 47 + -10V C1 0.1 + C2 0.1 0.1 or LINK COUT B BLACK LEVEL ADJUST R1 RV1 200 5 - 25pF CCOMP 50% GAIN CONTROL OFFSET 560 RV2 100 -5V B VIDEO INPUT R3 1k RV3 SPAN C3 ADJUST 0.1 R4 5.6k RV6 1k (0.5V) C5 0.1 VREF ADJUST 10 Z1 6.2V NOTE: C5 is used when the CONTROL VOLTAGE (V C) is derived from a power supply. All resistors in ohms, all capacitors in F unless otherwise stated. Fig. 1 Test Circuit 520 - 25 - 4 4 TYPICAL PERFORMANCE CURVES FOR GT4122 (Unless otherwise shown, VS = 10 V, RL = 10 k) -20 0.5 0.4 0.3 0.2 V IN = 150 mVp-p R COMP = 560 CCOMP = 18 pF CH-A -30 VIN = 1 Vp-p -40 GAIN (dB) GAIN (dB) 0.1 0.0 -0.1 -0.2 -0.3 -0.4 -0.5 1 1 60 60 -50 CH-A -60 -70 CH-B CH-B -80 -90 10 -100 1 1 100 10 100 FREQUENCY (MHz) FREQUENCY (MHz) Fig. 2 Frequency Response 0.03 -20 -30 -40 0.01 Fig. 3 Crosstalk vs Frequency 0.02 dg (%) / dp (deg) V C = 1Vp-p+0.5 VDC REF = 1Vp-p (0dB) 0.00 GAIN (dB) dg 10 -50 -60 -70 -80 -90 dp -0.01 -0.02 -0.03 1 3 5 -100 1 1 3 5 10 10 FREQUENCY (MHz) FREQUENCY (MHz) Fig. 4 Differential Gain & Phase vs Frequency Fig. 5 Crossfade Balance vs Frequency DOCUMENT IDENTIFICATION PRODUCT PROPOSAL This data has been compiled for market investigation purposes only, and does not constitute an offer for sale. ADVANCE INFORMATION NOTE This product is in development phase and specifications are subject to change without notice. Gennum reserves the right to remove the product at any time. Listing the product does not constitute an offer for sale. PRELIMINARY DATA SHEET The product is in a preproduction phase and specifications are subject to change without notice. DATA SHEET The product is in production. Gennum reserves the right to make changes at any time to improve reliability, function or design, in order to provide the best product possible. CAUTION ELECTROSTATIC SENSITIVE DEVICES DO NOT OPEN PACKAGES OR HANDLE EXCEPT AT A STATIC-FREE WORKSTATION Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. (c) Copyright April 1991 Gennum Corporation. All rights reserved. Printed in Canada. 5 520 - 25 - 4 |
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