Application Note 1348 Author: Bob Pospisil 1µF D2 S1AB S1AB J10 J11 VREF 0.1µF 1µF D1 C5 C4 0.01µF C8 C2 J9 J13 V+ DNP DNP C7 0.1µF R4 C1 The ISL28190 and ISL28191 amplifiers feature ultra-low noise, ultra-low distortion, and rail-to-rail output drive capability. They are designed to operate with single and dual supplies from +5.5VDC (±2.75VDC) down to +3VDC (±1.5VDC). 0.01µF V- R16 J7 The ISL2819xEVAL1Z evaluation board is a design platform containing all the circuitry needed to characterize critical performance parameters of the ISL28190 and ISL28191 single operational amplifiers, using a variety of user-defined test circuits. J8 ISL2819xEVAL1Z Evaluation Board User Guide Reference Documents • ISL28190 Datasheet • ISL28191 Datasheet FIGURE 1. POWER SUPPLY CIRCUIT Key Features D1 and D2, protect the circuit in case of accidental polarity reversal. The ISL2819xEVAL1Z is designed to enable the IC to operate from a single supply (+3VDC to +5.5VDC) or from split supplies (±1.5VDC to ±2.75VDC). The board is configured for a single op amp connected for differential input with a closed loop gain of 10. A single external reference voltage (VREF) pin is provided, as well as a user-selectable voltage divider (filter included). Amplifier Configuration (Figure 2) The schematic of the op-amp with the components supplied is shown in Figure 2. The circuit implements a differential input amp with a closed loop gain of 10. The circuit can operate from a single +3VDC to +5.5VDC supply, or from dual supplies from ±1.5VDC to ±2.75VDC. The VREF pin can be connected to ground to establish a ground-referenced input for split-supply operation, or it can be externally set to any reference level for single-supply operation. Power Supplies (Figure 1) External power connections are made through the V+, V- and ground connections on the evaluation board. For single-supply operation, the V- and ground pins are tied together to the power supply negative terminal. For split supplies, the V+ and V- terminals connect to their respective power supply terminals. De-coupling capacitors C2 and C4 are connected close to the power supply terminals. To filter out high-frequency noise, four additional capacitors (C1, C5, C7 and C8) are connected close to the part. Anti-reverse diodes, RF + IN- RIN- V+ 499Ω IN+ IN+ VCM 4.99kΩ VP IN- INRIN+ ISL2819x IN+ 50Ω VOUT V+ VM 499Ω RREF+ VREF VREF 4.99kΩ GND FIGURE 2. BASIC AMPLIFIER CONFIGURATION May 19, 2011 AN1348.1 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. Copyright Intersil Americas Inc. 2007, 2011. All Rights Reserved. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries. All other trademarks mentioned are the property of their respective owners. Application Note 1348 User-selectable Options (Figures 3 and 4) the VREF input. The inverting and non-inverting inputs have additional resistor placements for adding input attenuation, or to establish input DC offsets through the VREF pin. Component pads are included to enable a variety of user-selectable circuits to be added to the amplifier inputs, the VREF input, the outputs, and the amplifier feedback loops. The output (Figure 4) has a series 50Ω back-termination resistor to drive 50Ω cables, and additional resistor and capacitor placements for loading. A voltage divider and filter option (Figure 3) can be added to establish a power-supply-tracking common mode reference at C3 TO IN TO DUT OUTPUT IN + J2 R12 R2 J12 TO IN + 499 DNP OUTPUT R18 TO DUT OUTPUT 49.9 DNP 4.99k DNP DNP OPEN R17 499 C6 R9 0 DNP R5 R1 R7 IN J1 OPEN R11 R13 R15 DNP 4.99k VREF FIGURE 3. INPUT STAGE FIGURE 4. OUTPUT STAGE ISL2819xEVAL1Z Components Parts List DEVICE NUMBER DESCRIPTION COMMENTS C2, C4 CAP, SMD, 1206, 1µF, 100V, 10%, X7R, ROHS Power supply decoupling C1, C5 CAP, SMD, 0603, 0.01µF, 50V, 10%, X7R, ROHS Power supply decoupling C7, C8 CAP, SMD, 0603, 0.1µF, 50V, 10%, X7R, ROHS Power supply decoupling C3, C6 CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS User-selectable capacitors; not populated D1, D2 DIODE-RECTIFIER, SMD, 4.5X3.9mm, 50V, 1A, ROHS Reverse power protection U1 (ISL28190EVAL1Z) ISL28190FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS U1 (ISL28191EVAL1Z) ISL28191FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS R1-R4, R6-R8, R10, R13, R14, R16, R17, R20 RESISTOR, SMD, 0603, 0.1%, MF, DNP-PLACEHOLDER User-selectable resistors; not populated RES, SMD, 0603, 0Ω, 1/10W, TF, ROHS 0Ω user-selectable resistors R18 RES, SMD, 0603, 49.9Ω, 1/10W, 1%, TF, ROHS User-selectable output resistors R9, R12 RES, SMD, 0603, 499Ω, 1/10W, 1%, TF, ROHS Gain resistors R11, R15 RES, SMD, 0603, 4.99k, 1/10W, 1%, TF, ROHS Gain resistors RES, SMD, 0603, 10k, 1/10W, 1%, TF, ROHS User-selectable resistors R5, R21 R19 2 AN1348.1 May 19, 2011 Application Note 1348 ISL2819xEVAL1Z Top View 3 AN1348.1 May 19, 2011 Application Note 1348 J12 OUTPUT ISL2819xEVAL1Z Schematic Diagram DNP R17 OPEN J11 49.9 R18 C6 0.1µF VREF C8 0.01µF C5 J10 R6 R7 4.99k DNP VREF R15 499 R12 4.99k R9 499 0.1µF R3 C7 R20 DNP DNP R21 0 C3 OPEN R11 R10 DNP R8 DNP 0 J3 DNP R5 R4 IN- DNP J4 R14 DNP OUT J5 IN+ J7 J6 NODE S1AB C2 V- J13 1µF D1 DNP R13 U1 S1AB C4 1µF D2 V+ J8 SOT23_6 R16 J9 1 6 2 GENERIC 5 PACK. 3 4 DNP 0.01µF 10K ENABLEJ14 DNP DNP R2 IN + J2 IN - J1 R1 R19 2 S1 3 1 C1 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 4 AN1348.1 May 19, 2011