GB4570 Monolithic Video Buffer/Clamp DATA SHEET FEATURES DESCRIPTION • accurate sync tip clamping (± 2 mV typical) The GB4570 is a high performance video buffer/clamp used primarily for sync tip clamping of video signals. Key features • less than 1 mV clamping distortion include operation from ± 4.5 to ± 13.2 V supply voltages, ± 0.1 dB flatness to 80 MHz and availability of industry standard DIP + 3 V to V -4.5 V) • variable clamping voltage (V and SOIC packages. EE CC • ultra low differential gain and differential phase In a typical video application, the GB4570 clamps the sync tip to a known voltage. The clamping level can be set for normal • less than ± 0.15° phase delay variation at 3.58 MHz sync tip clamping by connecting pin 3 to - 0.286 volts. For applications requiring non-standard sync tip clamping, the • ± 0.1 dB flatness to 80 MHz clamping voltage applied to pin 3 may be varied. • ± 4.5 to ±13.2 V supply voltage range The GB4570 features a tight delay spread of only ± 0.15° at color burst frequencies and less than ± 1 millivolts clamping distortion. APPLICATIONS PIN CONNECTIONS • Sync tip clamping of NTSC, PAL, SECAM and RGB GB4570 Video Signals GND 1 8 V • Input buffering and clamping CC V 2 7 V IN OUT • Inter-system video signal clamping V 3 6 V CLAMP EE C 4 NC 5 HOLD SIMPLIFIED CIRCUIT DIAGRAM V CC 8 AVAILABLE PACKAGING 8 pin PDIP V 2 IN 8 pin SOIC COUPLING CAP 7 V OUT ORDERING INFORMATION Part Number Package Temperature Range 6 V EE GB4570-CDA 8 pin PDIP 0° to 70°C - + 50k GB4570-CKA 8 pin SOIC 0° to 70°C 3 V CLAMP GB4570-CTA 8 pin SOIC Tape 0° to 70°C 4 C HOLD Document No. 521 - 18 - 01 GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-2055 Japan Branch: A-302, Miyamae Village, 2-10-42, Miyamae, Suginami-ku, Tokyo 168, Japan tel. (03) 3247-8838 fax. (03) 3247-8839 ABSOLUTE MAXIMUM RATINGS PARAMETER VALUE/UNITS CAUTION ELECTROSTATIC Supply Voltage ±13.5 V SENSITIVE DEVICES DO NOT OPEN PACKAGES OR HANDLE Operating Temperature Range 0°C ≤ T ≤ 70°C A EXCEPT AT A STATIC-FREE WORKSTATION Storage Temperature Range -65°C ≤ T ≤150°C S Lead Temperature (soldering, 10 seconds) 260°C Differential Video Input Voltage ±5 V Strobe Input Voltage -V ≤ V ≤ +V S STROBE S ELECTRICAL CHARACTERISTICS V = ± 5 V, T = 0° to 70°C, R = 10kΩ, C = 10 pF, unless otherwise shown. S A L L PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage ±V ±4.5 ±5 ±13.2 V S POWER + Supply Current I+-914mA SUPPLIES - Supply Current I--914mA Small Signal B.W. B.W. ±0.1 dB after insertion loss, 80 - - MHz (flattened response) V =100 mV p-p IN Phase Delay ød at 3.58 MHz and 4.43 MHz -1.85 -2.0 -2.15 deg Differential Gain ∂g at 3.58 MHz and 4.43 MHz - 0.01 0.02 % Differential Phase ∂p at 3.58 MHz and 4.43 MHz - 0.01 0.02 deg V +3V - V -3V V Input Voltage V IN EE CC Input Resistance R 25 - - kΩ IN SIGNAL PATH Input Capacitance C - 2.0 - pF IN Output Resistance R ƒ= 0 to 1 MHz - 8.6 10 Ω OUT ƒ= 100 MHz - 20 40 Ω Insertion Loss I.L. ƒ= 100 kHz - 0.03 0.05 dB Power Supply Rejection Ratio PSRR ƒ= 1 kHz 50 - - dB ƒ= 10 MHz 30 - - dB PP Signal / RMS Noise S/N V =1 Vp-p 75 - - dB SIG Clamp Voltage Range V V = 1 Vp-p, V +3.0 - V -4.5 V CLAMP IN EE CC Accuracy V = 0.5V to 2Vp-p - ±2 ±7mV IN Clamping Distortion Amplitude during sync - - ±1mV 2 521 - 18 - 01 DETAILED DESCRIPTION The GB4570 is intended for video applications requiring DC With this automatic adjustment system, the need for an external restoration. The GB4570 signal path consists of a wideband sync separator circuit to enable the clamping action is Darlington emitter follower for maximum bandwidth eliminated. performance. With this configuration, the GB4570’s small The input to the GB4570 must be AC coupled using an signal frequency response remains within ± 0.1 dB of 0 dB out appropriately sized capacitor. This capacitor acts as a DC to 80 MHz. reservoir for corrective level shifts. Under equilibrium Optimal frequency response for the GB4570 occurs with load conditions, the average current supplied by the comparator capacitance in the range of 15 pF. For smaller loads, an output is just sufficient to balance the current discharging the external capacitor can be added to maximize the bandwidth input coupling capacitor. Under dynamic conditions, where of the device. As shown in Figure 1, a small resistor, R , the system is correcting for a change in the signal level, the OUT should be included in series with the GB4570 output to obtain charging current may be in the milliamp range. Since the optimal response flatness. For a nominal load of 15 pF, R corrective current is small under equilibrium conditions, the OUT should be chosen to be approximately 40 Ω. error voltage at the comparator input is also small making clamping to within ± 2 mV achievable. The DC restoration function is achieved through the use of a simple comparator. The non-inverting input of the comparator The circuit makes use of a ‘peak hold’ capacitor, C , at the HOLD is connected to the clamp reference voltage, while the inverting output of the comparator. This gives rise to a more constant input is connected to the GB4570 output. For output signals voltage at the comparator output. This constant voltage is more positive than the clamp reference voltage, the comparator translated to a more constant corrective current by an internal output is essentially open-circuit, while signal voltages more 50 kΩ resistor between the comparator output and the signal negative than the clamp reference voltage result in the charging input. of C , an external non-polar capacitor connected to pin 4. HOLD To avoid excessive phase shifts and consequent instability of The action of the comparator is to provide a positive current the clamp feedback loop, the peak hold capacitor should be which is fed back to the input under conditions where the considerably smaller (eg. 1000 times smaller) than the input device output is more negative than the clamp reference coupling capacitor. If faster clamping is desirable, the peak voltage. This negative feedback raises the DC level of the hold capacitor can be removed and a smaller input coupling input signal to the point where all signal fluctuations occur at capacitor employed. In this application, some distortion of the voltages above the clamp reference voltage. signal tip will occur. V V CC EE 0.1 0.1 8 6 VIDEO R OUT GB4570 CLAMPED V IN 2 7 SYNC TIP VIDEO 22 CLAMP OUTPUT 3 75 4 1 V CLAMP C LOAD C HOLD 1.1nF All resistors are in ohms, all capacitors in microfarads unless otherwise stated Fig. 1 Typical Application Circuit 3 521 - 18 - 01 +5V -5V +5V 0.1 0.1 0.1 1 8 6 NETWORK 1 R ANALYSER 10 S 4 8 VIDEO OUTPUT 2 7 GB4570 CLC110 TO NETWORK 5 Sweep: 1-100MHz ANALYSER I/P Level: 0dBM 4 3 75 C 10k L 0.01 0.1 +5V All resistors are in ohms, all capacitors in microfarads unless otherwise stated Fig. 2 Frequency Response Test Circuit TYPICAL PERFORMANCE CURVES 6.0 0.1 R = ø S C = 68pF L 0.05 C = 82pF L 4.0 C = 100pF 0 L C = 120pF L 2.0 R = 32.5Ω -0.05 S C = 180pF = 27pF C L L -0.1 R = 39Ω S 0.0 = 18pF C L -0.15 C = 270pF R = 43Ω L S = 10pF C L -2.0 -0.2 1 10 100 1 10 100 FREQUENCY (MHz) FREQUENCY (MHz) Fig. 3 GB4570 Frequency Response Fig. 4 Flattened Frequency Response 1 1 R = ø S 0 0 -1 -1 C = 270pF L R = 32Ω S -2 C = 27pF -2 C = 180pF L L R = 40Ω S -3 C = 120pF C = 18pF L -3 L -4 R = 43Ω C = 82pF S L -4 C = 10pF -5 L -5 -6 -7 -6 1 10 1 10 FREQUENCY (MHz) FREQUENCY (MHz) Fig. 6 Phase vs Frequency Fig. 5 Phase vs Frequency 4 521 - 18 - 01 GAIN (dB) PHASE (deg) GAIN (dB) PHASE (deg) 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. 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 September 1994 Gennum Corporation. All rights reserved. Printed in Canada. 5 521 - 18 - 01