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Moteur de recherche de fiches techniques de composants électroniques |
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Moteur de recherche de fiches techniques de composants électroniques |
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ISL59420 Fiches technique(PDF) 9 Page - Intersil Corporation |
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ISL59420 Fiches technique(HTML) 9 Page - Intersil Corporation |
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9 / 12 page  9 FN7459.1 September 22, 2005 Application Information General The ISL59420 is a 2:1 mux that is ideal as a matrix element in high performance switchers and routers. The ISL59420 is optimized to drive 5pF in parallel with a 500 Ω load. The capacitance can be split between the PCB capacitance and an external load capacitance. Its low input capacitance and high input resistance provide excellent 50 Ω or 75Ω terminations. Parasitic Effects on Frequency Performance Capacitance at the Inverting Input The AC performance of current-feedback amplifiers in the non-inverting gain configuration is strongly affected by stray capacitance at the inverting input. Stray capacitance from the inverting input pin to the output (CF), and to ground (CG), increase gain peaking and bandwidth. Large values of either capacitance can cause oscillation. The ISL59420 has been optimized for a 0.4pF to 0.7pF capacitance (CG). Capacitance (CF) to the output should be minimized. To achieve optimum performance the feedback network resistor(s) must be placed as close to the device as possible. Trace lengths greater than 1/4 inch combined with resistor pad capacitance can result in inverting input to ground capacitance approaching 1pF. Inverting input and output traces should not run parallel to each other. Small size surface mount resistors (604 or smaller) are recommended. Capacitance at the Output The output amplifier is optimized for capacitance to ground (CL) directly on the output pin. Increased capacitance causes higher peaking with an increase in bandwidth. The optimum range for most applications is ~1.0pF to ~6pF. The optimum value can be achieved through a combination of PC board trace capacitance (CT) and an external capacitor (COUT). A good method to maintain control over the output pin capacitance is to minimize the trace length (CT) to the next component, and include a discrete surface mount capacitor (COUT) directly at the output pin. Feedback Resistor Values The AC performance of the output amplifier is optimized with the feedback resistor network (RF, RG) values recommended in the application circuits. The amplifier bandwidth and gain peaking are directly affected by the value(s) of the feedback resistor(s) in unity gain and gain >1 configurations. Transient response performance can be tailored simply by changing these resistor values. Generally, lower values of RF and RG increase bandwidth and gain peaking. This has the effect of decreasing rise/fall times and increasing overshoot. Application Circuits FIGURE 25A. GAIN OF 1 APPLICATION CIRCUIT FIGURE 25B. GAIN OF 2 APPLICATION CIRCUIT VIN 50 Ω 200 Ω CG - + 0.4pF < CG < 0.7pF 0.6pF PC BOARD CAPACITANCE *CL: TOTAL LOAD CAPACITANCE COUT: OUTPUT CAPACITANCE CT: TRACE CAPACITANCE COUT RL = 500Ω VOUT 3.9pF *CL = CT + COUT CT 1.6pF VIN 50 Ω 453 Ω CG - + 453 Ω 0.4pF < CG < 0.7pF 0.6pF PC BOARD CAPACITANCE COUT RL = 500Ω VOUT 3.9pF *CL = CT + COUT CT 1.6pF ISL59420 |
Numéro de pièce similaire - ISL59420 |
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Description similaire - ISL59420 |
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