ISL281x8EVAL1Z Evaluation Board User’s Guide Application Note August 14, 2007 Introduction AN1350.0 R20 • ISL28138 Data Sheet, FN6336 R1 0 V+ C1 + 4.7µF D1 R24 R21 C2 + 4.7µF D2 0 Reference Documents J1 V- 0 The ISL28138 and ISL28148 high-speed operational amplifiers feature low power consumption, while the ISL28158 and ISL28168 operational amplifiers feature ultra-low power consumption. All op amps have rail-to-rail output drive capability and are designed to operate with a single lithium cell or two Ni_Cd batteries. J2 The ISL281x8EVAL1Z evaluation board is a design platform containing all the circuitry needed to characterize critical performance parameters of the ISL281x8 operational amplifiers, using a variety of user defined test circuits. J3 and V- terminals connect to their respective power supply terminals. De-coupling capacitors C1 andC2 connect to ground through R1 and R21 0Ω resistors. Resistors R20 and R24 are 0Ω but can be changed by the user to provide additional power supply filtering, or to reduce the voltage rate-of-rise to less than ±1V/µs. Two additional capacitors, C3 and C4 are connected close to the part to filter out high frequency noise. Anti-reverse diodes D1and D2 protect the circuit in the case of accidental polarity reversal. 0 ® • ISL28148 Data Sheet, FN6337 C4 C3 • ISL28158 Data Sheet, FN6377 0.1µF 0.1µF • ISL28168 Data Sheet, FN6378 VM Evaluation Board Key Features FIGURE 1. POWER SUPPLY CIRCUIT The ISL281x8EVAL1Z is designed to enable the IC to operate from a single supply, +2.4VDC to +5.5VDC or from split supplies, ±1.2VDC to ±2.75V. The board is configured for a single op amp connected for differential input with a closed loop gain of 10. It also contains a single external reference voltage (VREF) pin and provisions for a user-selectable voltage divider (filter are 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 supply or from dual supplies. The VREF pin can be connected to ground to establish a ground referenced input for split supply operation, or can be externally set to any reference level for single supply operation. Power Supplies (Figure 1) External power connections are made through the V+, Vand 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 V+ RF VP RIN- IN- IN- V+ 10kΩ RIN+ IN+ VCM GND IN+ 0Ω 0Ω VOUT V- + VM 10kΩ IN+ VREF ISL281x8 100kΩ IN - VREF VP RREF+ RL 100kΩ 10kΩ 10kΩ FIGURE 2. BASIC AMPLIFIER CONFIGURATION 1 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. 2007. All Rights Reserved All other trademarks mentioned are the property of their respective owners. Application Note 1350 User-selectable Options (Figures 3 and 4) The output (Figure 4) has a 10kΩ load resistor to ground, and has additional resistor and capacitor placements for loading. Component pads are included to enable a variety of user-selectable circuits to be added to the amplifier inputs, the VREF input, outputs and the amplifier feedback loops. NOTE: Operational amplfiers are sensitive to output capacitance and may oscilate. In the event of oscilation, reduce output capacitance by using shorter cables, or add a resistor in series with the output. J4 A voltage divider and filter option (Figure 3) can be added to establish a power supply-tracking common mode reference at 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. DNP RINA2+ 100k TO INC10 OPEN TO IN+ J5 OUT DNP R27 R25 10k 0 DNP R26 0 R23 R22 C9 OPEN C8 C5 + 4.7µF TO OUT OPEN 0 R6 R9 R3 DNP IN2+ J8 DNP OPEN RINA+ R11 DNP 10k C7 RREF RREFA+ R14 R13 RINA1+ R7 IN1+ J7 0 DNP R17 OPEN DNP RREFAR15 R12 R8 R2 DNP 10k RINA2- DNP R5 IN- J6 0 C6 10k RINAR10 R18 REF1 RGA+ FIGURE 4. 1/2 OUTPUT STAGE FIGURE 3. 1/2 INPUT STAGE ISL281x8EVAL1Z Components Parts List DEVICE NUMBER C1, C2, C5 DESCRIPTION COMMENTS CAP-TANTALUM,S MD, D, 4.7µF, 50V, 10%, LOW ESR, ROHS Power Supply Decoupling C3, C4 CAP, SMD, 0603, 0.1µF, 25V, 10%, X7R, ROHS Power Supply Decoupling C6 to C10 CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS User-selectable capacitors - not populated DIODE-RECTIFIER, SMD, SOD-123, 2P, 40V, 0.5A, ROHS Reverse Power Protection D1, D2 U1 (ISL28138EVAL1Z) ISL28138FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS U1 (ISL28148EVAL1Z) ISL28148FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS U1 (ISL28158EVAL1Z) ISL28158FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS U1 (ISL28168EVAL1Z) ISL28168FHZ-T7, IC-RAIL-TO-RAIL OP AMP, SOT-23, ROHS R2, R3, R6, R8, R9, R12, R13, RESISTOR, SMD, 0603, 0.1%, MF, DNP-PLACE HOLDER R15, R16, R23, R25, R27 User-selectable resistors - not populated R1, R10, R11, R17, R20, R21, RES, SMD, 0603, 0Ω, 1/10W, TF, ROHS R24, R26, R22 0Ω user selectable resistors R4, R5, R7, R18 RES, SMD, 0603, 10k, 1/10W, 1%, TF, ROHS Gain and other user selectable resistors R14, R19 RES, SMD, 0603, 100k, 1/10W, 1%, TF, ROHS Gain resistors 2 AN1350.0 August 14, 2007 Application Note 1350 ISL281x8EVAL1Z Top View 3 AN1350.0 August 14, 2007 Application Note 1350 J5 CLOSE TO PART OUT ISL281x8EVAL1Z Schematic Diagram DNP 0 VP V+ 10K C3 0.1µF R26 R27 R25 0 J1 4.7µF R23 C9 0 0 4.7µF J2 R22 0 R1 R21 C2 D1 DNP OPEN C1 R24 D2 OPEN VM C8 0 J3 4 SOT23_6 4 5 PACK. 5 3 GENERIC 3 2 2 1 1 U1 100k R19 6 6 VP 0.1µF C4 V- CLOSE TO PART R20 RREF 4.7µF VP C10 J8 IN2+ DISABLE ENABLE 1 3 10k 2 R4 DNP RINA2+ R6 OPEN S1 R11 0 RINA+ C7 10k R7 RINA1+ J7 IN1+ R5 OPEN R2 R3 10k RINA2DNP DNP J6 R8 R9 IN- DNP DNP C6 R12 0 OPEN R14 100k DNP R10 R16 RREFA+ DNP R15 RREFA- R13 J9 J4 REF1 DNP EN DNP R17 RINA- DNP 0 10k R18 RGA+ VM C5 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 AN1350.0 August 14, 2007