Linear LT6557 Quick Start Manual

5V TRIPLE HIGH SPEED VIDEO AMPLIFIER 1 LT6557 / LT6558 DESCRIPTION Demonstration Circuit 1016 (DC1016) is a 5V Triple High Speed Video Amplifier featuring the LT6557 or LT6558 in DFN packaging. The DC1016A–A version demonstrates the gain-of-two LT6557, while the DC1016A–B features the unity-gain LT6558. The board is designed to demon- strate AC-coupled performance in 5V single-supply op- eration. The LT6557 and LT6558 include automatic in- ternal biasing that is programmable with one resistor. Table 1 indicates the performance that is achieved with this evaluation board. Design files for this circuit board are available. Call the LTC factory. Table 1. Performance Summary (TA = 25°C) PARAMETER CONDITION VALUE Supply Voltage Recommended Min/Max +5V/+10V Supply Current V+ = 5V 65mA Input Impedance, INR, ING, INB 75Ω to ground, ac-coupled internal signals Output Impedance, OUTR, OUTG, OUTB 75Ω, ac-coupled CAL trace Impedance 75Ω nominal Outputs terminated into 75Ω 0dB nominal Gain (–A version) Outputs terminated into High impedance +6dB nominal Outputs terminated into 75Ω –6dB nominal Gain (–B version) Outputs terminated into High impedance 0dB nominal VIN = 125mVPP (-16dBm), –3dB, RL=75Ω 7Hz to 380MHz typical Frequency Response VIN = 125mVPP (-16dBm), ±0.1dB, RL=75Ω 7Hz to 130MHz typical Worst-case All Hostile, 10MHz –75dB typical Crosstalk Worst-case All Hostile, 100MHz –55dB typical Input Signal Voltage Range +5.0V Supply, No Output Clipping ±0.6V about average dc (–A) ±1.2V about average dc (–B) Logic Low Voltage (Amplifiers ON) ≤ (V +– 2)V On/Off Control Input Logic High Voltage (Amplifiers OFF) ≥ (V +– 0.5)V or open circuit OPERATING PRINCIPLES DC1016 provides three identical channels of wideband signal amplification suitable for driving HDTV or high- resolution RGB video display cables. The LT6557 pro- vides a gain of two for driving terminated video cables and the LT6558 has unity gain for use with high- impedance loads. Each amplifier section is provided with series “back-termination” at the outputs (included on the board), which results in unity gain transmission of a video signal to a destination load (75Ω for –A; 1kΩ or more for –B). Each input is dc terminated to analog ground to properly load the input signal cable. The in- puts are ac-coupled after termination to eliminate input

5V TRIPLE HIGH SPEED VIDEO AMPLIFIER 2 biasing requirements. The outputs are also ac-coupled to eliminate the amplifier bias from passing to the load. The dc-biasing at the amplifier inputs is programmed by the R7 resistor value. The internal input biasing circuitry behaves as a soft clamp, minimizing the need for exter- nal components in the signal path. The bias point is rela- tively fixed and independent of supply voltage changes. R7 and the input coupling capacitors may be removed if direct dc drive to the amplifiers is desired. A jumper, JP1, allows the LT6557 or LT6558 to be forced to an ENABLE condition. If JP1 is left in the EXTernal position, then enabling the LT6557 or LT6558 is accom- plished by pulling down the EN connection at least 2V below V+ by connection to E1 or J1. A 40kΩ pull-up re- sistor internal to the IC will provide a default shutdown mode of operation if the control input is left open-circuit; this allows open-collector type control of the amplifiers. A CAL trace is also provided on DC1016 to provide a means of precision calibration for a Network Analyzer (use the CAL connections when performing the “THRU” transmission calibration). The CAL trace has the same electrical performance and delay as the transmission lines of the three signal channels, thereby allowing most circuit board and connector effects to be eliminated from the transmission measurements. Figure 4 shows the material list of the components used by DC1016, and Figure 5 shows the electrical intercon- nection. QUICK START PROCEDURE Demonstration Circuit 1016 is easy to set up to evaluate the performance of the LT6557 or LT6558. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: NOTE: Due to the Ultra High Frequencies (UHF) involved, RF measurement practices are required to accurately evaluate the performance of the board. 1. Place jumpers in the following positions: ENABLE 2. Prior to connecting the power supply, preset the out- put voltage to +5V, or to the desired level, if different. 3. With power off, connect the power supply to V+ and GND using banana-plug cables. 4. If using a Network Analyzer, perform the THRU transmission cal with all cabling, adapters, impedance converters, etc. in place, and using the DC1016 CAL trace as the reference 0dB path. 5. Energize the power supply. 6. Connect the Network Analyzer (if used) to the appro- priate channels to measure frequency response and crosstalk as desired. Figure 2 shows a typical trans- mission plot. 7. For video-signal evaluation, connect a component- video signal source to the inputs and a monitor and/or video analyzer to the outputs, using equal-length ca- bling amongst the three video channels. Figure 3 shows a typical pulse response. 8. To evaluate the shutdown mode, disconnect or relo- cate the JP1 jumper to the EXT position (with no con- nections made at EN, or if present, a logic high pro- vided). JP1

5V TRIPLE HIGH SPEED VIDEO AMPLIFIER 3 COM + Power Supply +5.00 Inputs Outputs 5V-7.5V Figure 1. Recommended Demo Circuit Setup Figure 2. Typical Transmission Frequency Response

5V TRIPLE HIGH SPEED VIDEO AMPLIFIER 4 0 1 2 3 4 5 0 2 4 6 8 10 12 14 16 18 20 TIME (nS) OUTPUT (V) VIN = 1Vp-p VS = 5V RL = 150Ω ΩΩ Ω TA = 25°C Figure 3. Typical Time-Domain Transmission Response Figure 4. DC1016 Bill of Material (–A version shown)

5V TRIPLE HIGH SPEED VIDEO AMPLIFIER 5 Figure 5. DC1016 Electrical Schematic Diagram