ISL59440/41EVAL1 Evaluation Board User’s Guide ® Application Note August 9, 2005 AN1186.1 Introduction High Frequency Layout Considerations The ISL59440/41EVAL1 evaluation board contains all the circuitry needed to characterize critical performance parameters of the ISL59440, ISL59441 single 4:1 MUXamplifier, 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 ISL59440, ISL59441 are single-output, gain-selectable 4:1 MUX-amps. The unity- gain bandwidths are 400MHz for the ISL59440 and 900 MHz for the ISL59441. Each contain a common set of logic inputs for channel selection (S0, S1) three-state output control (HIZ) and an enable control input that powers down the device. 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 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 2A, 2B, and 2C. The evaluation board is supplied with the 75Ω back termination resistors shown in Figure 2C. • 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 placed 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 Shottky 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 1. ISL59440 Data Sheet, FN7459 2. ISL59441 Data Sheet, FN7458 EN0 S0 EN1 IN0 IN1 Amplifier Performance and Output Configurations DECODE EN2 The ISL59440, ISL59441 output amplifier is externally gainselectable with the non-inverting input directly coupled to the 4:1 MUX output. The inverting input is pinned out to the evaluation board. Resistor RF is set to the value shown in Figure 2D, and in conjunction with the amplifier internal capacitance, provides optimum frequency response with minimal gain peaking. 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 backterminated cable driving applications. Reference data sheets for additional performance data. 1 • Signal I/O lines are the same lengths and widths to match propagation delay and trace parasitics. S1 EN3 IN2 + OUT IN3 AMPLIFIER BIAS HIZ ENABLE FIGURE 1. ISL59440, ISL59441 FUNCTIONAL BLOCK CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | 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 1186 TABLE 1. LOGIC TABLE VIN 50Ω OR 75Ω ISL59440, ISL59441 RS, 0Ω + *Cb1 ~0.5pF RF S0 S1 HIZ ENABLE OUT 0 0 0 0 IN0 1 0 0 0 IN1 0 1 0 0 IN2 1 1 0 0 IN3 - - - 1 Power-down - - 1 - High Z *Cb2 ~3pF CL 1.5pF RL 500Ω * Cb1, Cb2 are approximate PCB trace capacitances. + RF + RF 475Ω Cb1 RL ~0.5pF 50Ω OR 75Ω 50Ω OR 75Ω FIGURE 2B. TEST CIRCUIT FOR 50Ω OR 75Ω TERMINATIONS TEST EQUIPMENT ISL59440, ISL59441 50Ω OR 75Ω 50Ω OR 75Ω RS * Cb1 is approximate PCB trace capacitance. FIGURE 2A. TEST CIRCUIT WITH OPTIMAL OUTPUT LOAD VIN TEST EQUIPMENT ISL59440, ISL59441 VIN RS 50Ω OR 75Ω Cb1 ~0.5pF 50Ω OR 75Ω PART # RF VALUE ISL59440 332Ω ISL59441 301Ω * Cb1 is approximate PCB trace capacitance. FIGURE 2C. BACK-TERMINATED TEST CIRCUIT FOR CABLE APPLICATION FIGURE 2D. RF TABLE FOR FIGURE 2 CIRCUITS ISL59440/41EVAL1 Top View 2 AN1186.1 August 9, 2005 Application Note 1186 ISL59440/41EVAL1 Schematic Diagram JENBAR 1 NIC ISL59440 ISL59441 2 IN0 IN0 R9 75Ω IN1 ENBAR EN 16 HIZ 15 3 NIC IN- 14 4 IN1 OUT 13 JHIZ R12 - 49.9Ω HIZ RF R14 - 49.9Ω OUT R5 - 75Ω R2 75Ω 5 GND IN2 R10 75Ω V+ 12 6 IN2 V- 11 7 NIC S1 10 JSO S1 R18 - 50Ω S0 9 8 IN3 IN3 C9 R20 D1 R1 75Ω SO R19 - 50Ω JSO C7 C2 C1 C3 10uF 0.1uF 10nF 1nF + D2 GND. V- + C8 C5 C4 C6 10uF 0.1uF 10nF 1nF V+ ISL59440/41EVAL1 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-Shottky, 2 Pin, 45V, 7.5A MBR0550T (Motorola) Reverse Polarity Protection R1, R2, R5, R9, R10 Resistor, SMD, 0603, 75Ω, 1/10W, 1%, Signal Input/output Termination R12, R14, R18, R19. Resistor, SMD, 0603, 49.9Ω, 1/16W, 1%, Logic Input Termination RF - ISL59440 Resistor, SMD, 0603, 332Ω, 1/10W, 1% Feedback Resistor RF - ISL59441 Resistor, SMD, 0603, 301Ω, 1/10W, 1% Feedback Resistor C9 CAP, SMD, 0603 Optional, not populated R20 Resistor, SMD, 0603 Optional, not populated U1 ISL59440/41 - 400/900 MHz MULTIPLEXING AMPLIFIER, 16PIN, 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 AN1186.1 August 9, 2005