Application Note 1595 ISL28218SOICEVAL1Z Evaluation Board User’s Guide Introduction Power Supplies (Figure 1) The ISL28218SOICEVAL1Z evaluation board is designed to evaluate the performance of the ISL28218 40V Precision Low Power Operational Amplifier. The ISL28218 is a single supply rail-to-rail output, dual amplifier with ground sensing inputs that allow the common mode input voltage to swing 0.5V below the V- rail. The ISL28218 can operate from a single or dual supply with a 3V to 40V supply range. The ISL28218 features very low power, low offset voltage and low temperature drift making them ideal for applications for precision medical and instrumentation, current sensing and power supply and industrial process controls. External power connections are made through the V+, V-, VREF, and GND connections on the evaluation board. The circuit can operate from a single supply or from dual supplies. For single supply operation, the V- and GND pins are tied together to the negative or ground reference of the power supply. For split supplies, V+ and V- terminals connect to their respective supply terminals. De-coupling capacitors C2 and C4 provide low-frequency power-supply filtering, while additional capacitors, C3 and C5, which are connected close to the part, filter out high frequency noise. Anti-reverse diode D1 (optional) protects the circuit in the momentary case of accidentally reversing the power supplies to the evaluation board. 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. C4 1µF 1µF 1 2 • Convenient PCB pads for Op Amp Input/Output impedance loading. 1 1 0 1 R16 2 1 C2 3 • BNC Connectors for Op Amp Input and Output Terminals VREF J14 • Banana Jack Connectors for Power Supply and VREF Inputs 3 2 J13 3 2 • External VREF input V+ J8 V- • Singled-Ended or Differential Input Operation J12 • Dual Supply Operation: ±1.5V to ±20V 1 J6 J11 • Single Supply Operation: +3V to +40V 0 Evaluation Board Key Features 1 R31 2 1 • ISL28218 Datasheet, FN7532 1 Reference Documents D1 CLOSE TO DUT C3 C5 0.01µF 0.01µF FIGURE 1. POWER SUPPLY CIRCUIT R13/R23 100kΩ LOAD R11/R24 RSENSE INA- 2 INB- 6 10kΩ R14/R21 INA+ 3 INB+ 5 8 - V+ ISL28218 V- +3V TO 40V 1/7 + 4 10kΩ VOUT GAIN = 10V/V R18/R19 100kΩ VREF FIGURE 2. CURRENT SENSE AMPLIFIER October 27, 2010 AN1595.0 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. 2010. All Rights Reserved All other trademarks mentioned are the property of their respective owners. Application Note 1595 Amplifier Configuration (Figure 3) User-selectable Options (Figures 3 and 4) The schematic of the op amp input stage with the components supplied is shown in Figure 3, with a closed loop gain of 10V/V. The differential amplifier gain is expressed in Equation 1: 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. (EQ. 1) V OUT = ( V IN+ – V IN- ) • ( R F ⁄ R IN ) + V REF For single-ended input with an inverting gain G = -10V/V, the IN+ input is grounded and the signal is supplied to the IN- input. VREF can be connected to a reference voltage between the V+ and V- supply rails. For non-inverting operation with G = 11V/V, the IN- input is grounded and the signal is supplied to the IN+ input. The non-inverting gain is strongly dependent on any resistance from IN- to GND. For good gain accuracy, a 0Ω resistor should be installed on the empty R5 pad. C1 R26 FROM VOUTA 100k J15 VOUT_A 0 C6 OUT A DNP 10k NOTE: Operational amplifiers are sensitive to output capacitance and may oscillate. In the event of oscillation, reduce output capacitance by using shorter cables, or add a resistor in series with the output. OPEN R28 0 OPEN R13 The output (Figure 4) also has additional resistor and capacitor placements for filtering and loading. C8 R1 DNP R11 DNP R4 J1 R5 IN-A A voltage divider (Figure 3, R18 and R15) can be added to establish a power supply-tracking common mode reference using 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. OPEN TO INA R14 IN+A J2 R2 TO INA + FIGURE 4. OUTPUT STAGE 10k DNP R15 R18 DNP 100k VREF FIGURE 3. INPUT STAGE TABLE 1. ISL28218SOICEVAL1Z COMPONENTS PARTS LIST DEVICE # DESCRIPTION COMMENTS C2, C4 CAP, SMD, 1206, 1µF, 50V, 10%, X7R, ROHS Power Supply Decoupling C3, C5 CAP, SMD, 0603, 0.01µF, 50V, 10%, X7R, ROHS Power Supply Decoupling CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS User selectable capacitors - not populated RESISTOR, SMD, 0603, 10kΩ, 1%, 1/16W, ROHS Gain Setting Resistor RESISTOR, SMD, 0603, 100kΩ, 1%, 1/16W, ROHS Gain Setting Feedback Resistor C1, C6, C7, C8, C9, C10 R11, R14, R21, R24 R13, R23 R1-R3, R5-R8, R10, R12, RESISTOR, SMD, 0603, DNP-PLACE HOLDER, ROHS R15, R17, R20, R22, R28R30, R32, R34-R36 D1 U1 (ISL28218FBZ) 40V DUAL SERIES SCHOTTKY BARRIER DIODE User selectable resistors - not populated Reverse Power Protection ISL28218FBZ, IC 40V RAIL-TO-RAIL OP AMP, SOIC, ROHS 2 AN1595.0 October 27, 2010 Application Note 1595 ISL28218SOICEVAL1Z Top View 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 AN1595.0 October 27, 2010 ISL28218SOICEVAL1Z Schematic Diagram J11 J6 J14 3 VREF J13 3 J12 V+ J8 V- C4 1 1 0 1 1 R16 2 1 0 1 C2 3 4 1µF 1 R31 2 1 2 2 1µF 1 2 D1 CLOSE TO DUT C3 C5 0.01µF R8 2 DNP 3 4 1 OPEN 1 R28 2 DNP C8 2 J24 0 1 2 OUT B 3 4 1 OPEN R29 1 2 DNP 2 C7 1 OPEN 1 R27 2 C9 DNP 1 R36 2 DNP R35 1 R25 2 1 2 0 DNP 1 R20 2 2 DNP R30 J23 J21 J20 J19 J18 J17 R6 2 DNP 1 2 1 DNP R5 1 DNP R3 2 1 4 3 4 3 4 3 4 3 IN+B 1 J4 2 1 5 R7 2 DNP OPEN 1 R26 2 0 2 1 R15 2 1 R18 2 1 R19 2 1 R22 2 100k 100k DNP DNP 1 2 1 1 IN-B 2 R24 2 1 R23 2 1 10k 100k C10 1 8 2 1 8 U1 OPEN 2 OPEN 2 SOIC8 7 7 1 R14 2 3 3 GENERIC 6 6 PACK. R21 2 10k 4 4 5 51 10k R4 2 1 R11 2 1 R13 2 0 10k 100k 2 C1 1 1 IN- 1 R32 2 1 R34 2 DNP DNP VREF J3 5 1 2 DNP 2 R2 2 DNP R12 1 1 2 1 2 1 2 1 1 J2 5 1 R1 2 DNP 2 IN+A 1 2 R10 DNP 1 J1 5 2 2 2 IN-A 1 1 1 1 OUT NODE IN+ J22 IN+ NODE OUT 1 R17 2 DNP IN- OUT A 1 J15 2 5 1 J16 5 Application Note 1595 2 C6 2 0.01µF AN1595.0 October 27, 2010