ISL59444EVAL1 Evaluation Board User’s Guide ® Application Note April 19, 2005 AN1184.0 Introduction High Frequency Layout Considerations The ISL59444EVAL1 evaluation board contains all the circuitry needed to characterize critical performance parameters of the ISL59444 single 4:1 MUX-amplifier, over a variety of applications. At frequencies of 500MHz and higher, circuit board layout may limit performance. The following layout guidelines are implemented on the evaluation board: The ISL59444 is a single-output 4:1 MUX-amps with a unitygain bandwidth of 1GHz. The device contains logic inputs for channel selection (S0, S1) three-state output control (HIZ) that allows individual selection of MUX amps that share a common video output line. Latches LE1 and LE2 provide synchronous switching of the channel select logic to the output. The evaluation board circuit and layout is optimized for either 50Ω or 75Ω terminations, and implements a basic single 4:1 video MUX-amp. The board is supplied with 75Ω input signal terminations and a 75Ω back-termination resistor on each of the 3 outputs, making it suitable for driving video cable. The user has the option of replacing the 75Ω resistors with 50Ω resistors for other applications. The control lines contain 50Ω resistors to match the 50Ω output impedance of high speed pulse generators. Control line termination resistors are recommended for rise and fall times under 10ns to minimize unwanted transients. If DC is used for the control logic, the resistors may be removed; or the applied DC voltage can be reduced to 2.5V to reduce the dissipation in the termination resistor. The layout contains component options to include an output series resistor (RS) followed by a parallel resistor (RL) capacitor (CL) network to ground. This option allows the user to select several different output configurations. Examples are shown in Figures 3A, 3B, and 3C. The evaluation board is supplied with the 75Ω back termination resistors shown in Figure 3C. • Signal I/O lines are the same lengths and widths to match propagation delay and trace parasitics. • No series connected vias are used in signal I/O lines, as they can add unwanted inductance. • Signal trace lengths are minimized to reduce transmission line effects and the need for strip-line tuning of the signal traces. • High frequency decoupling caps are places as close to the device power supply pin as possible - without series vias between the capacitor and the device pin. Power Sequencing Proper power supply sequencing is -V first, then +V. In addition, the +V and -V supply pin voltage rate-of-rise must be limited to ±1V/µs or less. The evaluation board contains parallel-connected low VON Schottky diodes on each supply terminal to minimize the risk of latch up due to incorrect sequencing. In addition, extra 10µF decoupling capacitors are added to each supply to aid in reducing the applied voltage rate-of-rise. Reference Documents • ISL59444 Data Sheet, FN7451 EN0 DL Q C DL Q C EN1 DL Q C DL Q C EN2 DL Q S0 DECODE S1 HIZ Amplifier Performance and Output Configurations EN3 The ISL59444 output amplifier is sensitive to capacitance at the output. For best AC performance, a series output resistor is required to reduce excessive gain peaking, particularly when long PB board traces are used. The output amplifier is ideally suited for driving high impedance high speed selectable-gain buffers when gain compensation is needed. GBW decreases slightly at the lower output load impedances typical of back-terminated cable driving applications. Reference data sheets for additional performance data. LE1 LE2 C DL Q C DL Q C DL Q C IN0 OUT IN1 IN2 IN3 100kΩ 100kΩ FIGURE 1. ISL59444 FUNCTIONAL BLOCK DIAGRAM LE1 LE2 S0, S1, HIZ OUT CHX CHX CHY CHZ CHY CHX CHX CHZ CHZ FIGURE 2. ISL59444 TIMING DIAGRAM 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-352-6832 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2005. All Rights Reserved All other trademarks mentioned are the property of their respective owners. Application Note 1184 TABLE 1. LOGIC TABLE ISL59444 VIN 50Ω OR 75Ω S0 S1 LE1/LE2 HIZ OUT 0 0 0 0 IN0 1 0 0 0 IN1 0 1 0 0 IN2 1 1 0 0 IN3 - - 0 1 High Z - - Timing Diagram 0 Timing Diagram ISL59444 RS, 0Ω VIN *Cb2 ~3pF Cb1 ~0.5pF 500Ω * Cb1, Cb2 are approximate PCB trace capacitances. 50Ω OR 75Ω FIGURE 3B. TEST CIRCUIT FOR 50Ω OR 75Ω TERMINATIONS ISL59444 50Ω OR 75Ω 50Ω OR 75Ω * Cb1 is approximate PCB trace capacitance. FIGURE 3A. TEST CIRCUIT WITH OPTIMAL OUTPUT LOAD VIN 475Ω Cb1 RL ~0.5pF 50Ω OR 75Ω RL TEST EQUIPMENT RS RS 50Ω OR 75Ω Cb1 ~0.5pF TEST EQUIPMENT 50Ω OR 75Ω * Cb1 is approximate PCB trace capacitance. FIGURE 3C. BACK-TERMINATED TEST CIRCUIT FOR CABLE APPLICATION ISL59444EVAL1 Top View 2 AN1184.0 April 19, 2005 Application Note 1184 ISL59444EVAL1 Schematic Diagram ISL59444 IN0 R9 75Ω IN1 R2 75Ω 1 IN0 V+ 16 2 GND S0 15 3 IN1 S1 14 HIZ 13 4 GND IN2 OUT 12 5 IN2 R10 75Ω IN3 R11 75Ω JS0 S0 JS1 R19 - 49.9Ω S1 JHIZ R18 - 49.9Ω HIZ R12 - 49.9Ω OUT RS - 75Ω 6 GND LE2 11 7 IN3 LE1 10 V- 8 8 GND R21 C10 R6 - 49.9Ω LE2 R5 - 49.9Ω LE1 D1 C3 10µF C2 0.1µF C1 10nF C7 1nF + C6 10µF D2 + GND V- C5 0.1µF C4 10nF C8 1nF V+ ISL59444EVAL1 Components Parts List DEVICE # DESCRIPTION COMMENTS C7, C8 CAP, SMD, 0603, 1000pF, 25V, 10%, X7R Power Supply Decoupling C1, C4 CAP, SMD, 0603, 0.01µF, 25V, 10%, X7R Power Supply Decoupling C2, C5 CAP, SMD, 0603, 0.1µF, 25V, 10%, X7R Power Supply Decoupling C3, C6 CAP, SMD, 0805, 10µF, 6.3V, 10%, X5R Power Supply Decoupling D1, D2 Diode-Schottky, 2 Pin, 45V, 7.5A MBR0550T (Motorola) Reverse Polarity Protection R2, R9, R10, R11, RS Resistor, SMD, 0603, 75Ω, 1/10W, 1% Signal Input/output Termination R5, R6, R12, R18, R19 Resistor, SMD, 0603, 49.9Ω, 1/16W, 1% Logic Input Termination C10 Resistor, SMD, 0603 Optional, not populated R21 Resistor, SMD, 0603 Optional, not populated U1 ISL59444 - 1GHz Multiplexing Amplifier, 16P, QSOP Device Under Test Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the Application Note or Technical Brief is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com 3 AN1184.0 April 19, 2005