GB4550 & GB4550A Monolithic Video Buffer/Clamp DATA SHEET FEATURES DESCRIPTION • adjustable clamp level from -5.5 V to +5.5 V at ±10 V supplies. • ultra low differential gain (0.02% typ.) and differential phase (0.03° typ.) • wideband unity gain: GB4550 ±0.2 dB at 25 MHz GB4550A ±0.1 dB at 25 MHz • both drive 150pF loads at full power, flat to 10 MHz. • GB4550A — tight delay spread of ±0.15°at colorburst. • convenient 8 pin SIP packaging. • both can be configured as a gain stage with reduced bandwidth. PIN CONNECTIONS The GB4550 and GB4550A are high performance monolithic video buffer/clamps made on Gennum's LSI process. They feature a wideband differential amplifier that can be configured as a gain stage. The output signal voltage is limited to +2V above the clamp level in order to prevent damage to crosspoints connected to the output. The clamping level can be set for normal sync tip clamping by connecting pin 4 to -0.286 volts. For other applications, the clamping voltage level can be varied from -5.5 to +5.5 volts. The GB4550A features a tight delay spread of only ± 0.15 degrees while the GB4550 maintains a ± 1.5 degree delay spread. Both devices operate from ± 9 to ± 12 V power supplies and will directly interface with Gennum's video crosspoint switches. The 8 pin SIP package is ideally suited for space restricted board layouts. GB4550 and GB4550A APPLICATIONS • Input buffering and clamping to crosspoint switches 1 2 3 4 5 6 7 • Inter - system video signal clamping 8 CX Pin No. GB4550 GB4550A Function 1 +IN +IN non-inverting input 2 VCC VCC positive power supply 3 COMP NC frequency compensation or NC 4 VCL VCL clamp voltage input 5 CX CX external capacitor 6 VEE V EE negative power supply 7 -IN -IN inverting input 8 OUT OUT output (+2 V OUTPUT CLAMP) 100k 30k (NC on GB4550A) + COMP VCL 10pF +IN + -IN - 30k VCC OUT 7mA Nominal VEE ORDERING INFORMATION Part Number Package Type All resistors in ohms, all capacitors in microfarads unless otherwise stated Temperature Range GB4550 - CSA 8 pin SIP 0 to 70oC GB4550ACSA 8 pin SIP 0 to 70o C SIMPLIFIED CIRCUIT DIAGRAM Revision Date: February 1994 Document No. 520 - 34 - 4 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 VALUE ± 13.5 V Supply Voltage VS -65°C ≤ TS ≤ 150° C Storage Temperature Range Lead Temperature (Soldering, 10 Sec) 260° C ±5 V Differential Video Input Voltage VEE + 2.5 V ≤ VCL ≤ Vcc - 2.5 V ELECTRICAL CHARACTERISTICS PARAMETER POWER SUPPLIES SIGNAL PATH GB4550 SIGNAL PATH V S = ± 10 V, TA = 0 - 70°C, R L = 10kΩ, CL = 150 pF, CCOMP = 0 pF unless otherwise shown. SYMBOL - 9 13.8 mA I- - 9 13.8 mA VIN MAX 1.8 2.0 2.25 V - - 0.03 dB - Supply Current I.L. Operating Range ƒ = 100kHz Full Power Bandwidth FPBW -3.0dB, V IN = 1V p-p 15 18 - MHz Small Signal Bandwidth SSBW ± 0.2dB, V IN = 100mV p-p 20 25 - MHz at 10MHz, VIN = 1V p-p - 0.05 - dB at 3.58MHz - -8 - deg at 3.58MHz - ± 1.5 - deg Frequency Response øD Full Power Bandwidth FPBW -3.0dB, V IN = 1V p-p 17 20 - MHz Small Signal Bandwidth SSBW ± 0,1dB, V IN=100mV p-p, C L=100pF 25 30 - MHz at 10MHz, VIN = 1V p-p - 0.1 - dB at 3.58 MHz - -7.5 - deg at 3.58MHz - ± 0.15 - deg Frequency Response Signal Path Delay øD Differential Gain dg at 3.58MHz - 0.02 0.05 % Differential Phase dp at 3.58MHz - 0.03 0.05 deg Input Resistance RIN 80 100 - kΩ Input Capacitance CIN - 2.0 - pF Output Resistance R OUT - 8.6 53 - Ω Ω -5.5 - +5.5 V - 7 28 mV Clamp Voltage Range 520 - 34 - 4 UNITS I+ Delay Tolerance CLAMP MAX V Delay Tolerance SIGNAL PATH TYP ± 12 + Supply Current Insertion Loss MIN ± 10 VS Maximum Input Voltage Above VCL CONDITIONS ±9 Supply Voltage Signal Path Delay GB4550A SIGNAL PATH DO NOT OPEN PACKAGES OR HANDLE EXCEPT AT A STATIC-FREE WORKSTATION 0°C ≤ TA ≤ 70° C Operating Temperature Range Clamp Input Voltage CAUTION ELECTROSTATIC SENSITIVE DEVICES Clamp Accuracy AV = +1, ƒ = 0 to 10MHz AV = +1, ƒ = 100MHz V CL VIN = 1V p-p 2 DETAILED DESCRIPTION The GB4550(A) is intended for video applications requiring coarse DC restoration coupled with flat frequency response. As shown in Figure 1, the signal path features a wide band operational amplifier designed to be unity gain stable. While this amplifer is not intended to drive 75 Ω transmission lines, it is ideal for applications where high capactive loads, up to several hundred picofarads, must be driven, such as input buffering and DC restoration of video signals. Under equilibrium conditions the average current supplied by the comparator output is just sufficient to balance the current discharging the input capacitor. This discharge current is simply the input bias current of the op-amp, typically less than 20 µA . However, an external resistor can be added to increase the pull down current. Under dynamic conditions, where the system is adjusting for a change in the signal level, the charging current may be in the milliamp range. Because the corrective current is small under equilibrium conditions, the error voltage at the comparator input is small also, so clamping accuracy to within ± 7 mV is achievable. Optimal frequency response for the GB4550(A) occurs with load capacitances in the range of 80 pF to 100 pF as shown in Figure 4. For smaller loads, an external capacitor can be added to extend the bandwidth and improve the flatness of the device response. The clamp circuit makes use of a "peak hold" capacitor, CX, at the output of the comparator . This gives rise to a more constant voltage at the comparator output which is translated to a more constant corrective current by an internal 100 kΩ resistor connected between the comparator output and the signal input. The clamping function is achieved through the use of a simple comparator. The inverting input of the comparator is connected to the GB4550(A) output, while the non-inverting input is connected to the clamp voltage reference. For output signal voltages more positive than the clamp reference the comparator output is essentially open-circuit, while signal voltages more negative than the clamp reference result in the charging of CX. The action of the comparator is to provide a positive current which is fed back to the op-amp non-inverting input under conditions where the op-amp output is more negative than the clamp reference voltage. This negative feedback raises the DC level of the input signal to the point where all signal fluctuations occur at voltages above the clamp reference level. This is the desired clamp action. To avoid excessive phase shift and consequent instability of the clamp feedback loop, the peak hold capacitor needs to be considerably smaller (e.g. 1000 times) than the input coupling capacitor. If a faster clamp is desirable (e.g. for 60 Hz hum elimination) the peak hold capacitor can be removed and a smaller input coupling capacitor employed. In this application some distortion of the signal "tip" is unavoidable. The input to the op-amp must be AC coupled using an appropriate size of capacitor, which then acts as a DC "reservoir" for the corrective level shift. CX (+2 V OUTPUT CLAMP) 100k 30k (NC on GB4550A) + COMP VCL 10pF +IN + -IN - 30k VCC 7mA Nominal OUT VEE All resistors in ohms, all capacitors in microfarads unless otherwise stated. Fig. 1 Simplfied Circuit Diagram 3 520 - 34 - 4 +10V -10V 0.1 +5V 0.1 0.1 2 4 6 1 0.1 *22 SIGNAL IN FROM NETWORK ANALYSER 1 8 D.U.T. 4 CLC110 NON-POLAR OUTPUT TO NETWORK ANALYSER 8 5 7 5 3 10k 75 **RCOMP -5V 10n All resistors in ohms, all capacitors in microfarads unless otherwise stated. **CCOMP CLOAD 0.1 NOTES: This circuit can be used for Frequency Response, Delay and Differential Gain and Phase measurements. * This input capacitor must be shorted out when performing Differential Gain and Phase tests. ** RCOMP and CCOMP are only used on GB4550. Fig. 2 Test Circuit +10V 0.1 VIDEO OUT 1 0.1 4 2 VIDEO IN GX4314 XPOINT -10V GB4550 GB4550A 0.1 to 22 1 GX4314 XPOINT 6 NON-POLAR 8 7 5 VIDEO OUT 2 3 GX4314 XPOINT VIDEO OUT 3 GX4314 XPOINT VIDEO OUT 4 *RCOMP All resistors in ohms, all capacitors in microfarads unless otherwise stated. **10n *CCOMP CLOAD NOTES: In most applications RCOMP and CCOMP will not be needed since the bandwidth depends on the bus capacitance. In general, the maximum occurs when CLOAD is between 82 pF and 100 pF. They are used to control the roll-off for higher load conditions. * Not used on GB4550A. ** The value of this capacitor should be proportional to the input capacitor used. The value shown is for a 22 µF input capacitor. Fig. 3 Typical Application Circuit 520 - 34 - 4 4 TYPICAL PERFORMANCE CURVES Unless otherwise shown SV = ±10V 0.5 -3 0.4 CL = 180 pF 0.3 0.1 150 pF DEGREES GAIN (dB ) 0.2 0 -0.1 120 pF -0.2 -0.3 82 pF -0.4 -0.5 1 1 40 10 40 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 -4123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 -5123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 dpCL = 100 pF 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 -6123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 -7123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 -8123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 dg 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 -9123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 123456789012345678901234567890121234567890123 -10 2 2 3 4 5 FREQUENCY (MHz) Fig. 4 GB4550 Frequency Response 0.5 Fig. 5 GB4550 Phase Delay Spread -3 CL = 180 pF CL = 100 pF 0.1 DEGREES GAIN ( dB ) 0.3 0 -0.1 CL = 82 pF -0.3 -0.5 1 1 6 6 FREQUENCY (MHz) 40 10 40 -4 1234 1234 1234 1234 1234 1234 1234 CL = 100pF 1234 1234 1234 12345 1234 1234 1234 12345 1234 -5 1234 1234 12345 1 234 1234 1234 1234 12341234 1234 1234 1234 1234 1234 1234 -6 1234 1234 1234 1 2345 1234 1234 1234 12345 1234 1234 12345 12345 1234 1 234 12345 1234 1234 1234 12345 -7 1 23 1234 1234 1 234 123 1234 1234 1234 123 1234 1234 1 23 1234 1234 1234 123 -8 1234 1234 123 1234 1234 123 1234 1234 123 1234 1234 123 -9 1234 1234 123 1234 1234 123 1234 123 1234 -10 2 2 3 4 5 FREQUENCY (MHz) 6 6 FREQUENCY (MHz) Fig. 6 GB4550A Frequency Response Fig. 7 GB4550A Phase Delay Spread 0.05 REVISION NOTE: Detailed Description added dg (%) / dp (°) 0.03 dg 0.01 DOCUMENT IDENTIFICATION dp 0 PRODUCT PROPOSAL This data has been compiled for market investigation purposes only, and does not constitute an offer for sale. -0.01 V IN = 40 IRE 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. -0.03 -0.05 1 1 3 5 10 10 PRELIMINARY DATA SHEET The product is in a preproduction phase and specifications are subject to change without notice. FREQUENCY (MHz) 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. Fig. 8 Differential Gain and Phase Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. © Copyright April 1991 Gennum Corporation. All rights reserved. Printed in Canada. 5 520 - 34 - 4