Application Note 1753 ISL28617VYXXEV1Z User’s Guide Introduction The ISL28617VYXXEV1Z evaluation board is designed to assess the ISL28617 instrumentation amplifier’s (in-amp) performance with Bulk Metal® Foil resistors from Vishay Precision Group. With a differential input voltage range up to ±34V, a supply voltage range of 8V (±4V) to 40V (±20V) and gain ranging from 0.1 to 10,000, this precision in-amp is ideal for a wide variety of applications. It features differential inputs and outputs, and can drive the output rail-to-rail. The gain accuracy is limited only by the matching of the gain resistors. Reference: Vishay Precision Group’s foil resistors at http://www.vishaypg.com/ppg?63209. The FRSM series Bulk Metal® Foil ultra-high precision resistors have a tolerance of 0.01% and a temperature coefficient (TCR) of 0.2 ppm/°C, giving exceptional gain accuracy that is ideal for high end applications. The foil resistors are capable of achieving tighter absolute and ratio tolerances than any other technology. The real value of foil resistors is their unmatched stability through temperature excursions, load life and extraordinary thermal and environmental stresses, resulting in far more stable gain ratios. Another important feature of the Bulk Metal® Foil technology is the lowest current noise of any resistor technology (<- 40 dB). The combination of foil resistors’ low current noise and the exceptional low-noise performance of the ISL28617 amplifier make this the perfect solution for noise critical precision applications. The board is configured for ease of use, but allows for more complex variations to fit the user’s need. The evaluation board includes test points (VCC, VEE, and GND) for the power supply inputs, and is configured for operation from split supplies between ±4V to ±20V. There are two pairs of test points for the differential input and output as well (VIN+, VIN-, VOUT+, and VOUT-). The board is available in three different gain configurations: 0.25, 10 and 100. Ordering information is shown in Table 3. Reference Documents • ISL28617 Data sheet, FN6562 • FRSM Vishay Foil Resistor Data sheet, Document Number: 63209 Power Supplies supply voltages for the three standard boards. For more information, reference “Setting the Power Supply Voltages” on page 13 of the ISL28617 data sheet. If the user wants to control the output supplies separately, the R3 and R5 resistors must be removed, and the VCO (TP2) and VEO (TP6) test points are used for the positive output supply and negative output supply respectively (reference evaluation board schematic in Figure 4). Single supply operation requires removing R7 and attaching the desired common mode voltage to the VREF (TP10) test point. Using the separate supply feature enables input signals riding on a high common mode voltage to be level shifted to a low voltage device, such as an analog to digital converter (ADC). The rail-to-rail output stage can be powered from the same supplies as the ADC while preserving the in-amp’s maximum input dynamic range. Once again, the positive input power supply must be 3V above the maximum output signal, and the negative input power supply must be 3V below the minimum output signal. Amplifier Configuration The ISL28617 evaluation board schematic is shown in Figure 4 with a closed loop gain of 10 and split supply operation with input and output supplies tied together. Other gain options are 0.25 and 100, with the required resistor and capacitor changes listed in Table 1. The in-amp gain is controlled through R1 and R2, the feedback and input resistors, with the following simple formula: R1 A V = ------R2 (EQ. 1) R1 and R2 also limit the maximum signal size at the input and output due to the amplifier architecture. Table 2 shows the signal limits for the boards at the preset resistor values. For more information, refer to “Setting the Feedback Gain RFB" and “Setting the Input Gain RIN” on page 13 of the ISL28617 data sheet. The evaluation board allows the user to add an optional low pass RC filter to the signal path. R8, R9, and C6 create a filter on the output of the in-amp, while R10, R11, and C7 create a filter on the input. The gain of 0.25 board option includes a filter on the input to avoid gain peaking at the limits of the gain bandwidth product. External power connections are made to the positive supply rail (TP1), the negative supply rail (TP9), and ground (TP4) for split supply operation. The operating voltage range is ±4V to ±20V. The in-amp has two distinct sets of power supplies; one on the input stage and one on the output stage. For the evaluation board, the output stage supplies are tied to the input stage supplies, and the common mode voltage is tied to ground. The supply voltage on the input stage must be 3V above and below the maximum and minimum input signal voltage, respectively. Note that while the output stage is rail-to-rail, the feedback returns to the input stage, which is not rail-to-rail. Therefore, the input power supply must be 3V above and below the maximum and minimum output signal as well. Table 2 provides suggested September 26, 2012 AN1753.2 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. Copyright Intersil Americas Inc. 2012. 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 1753 TABLE 1. COMPONENTS PARTS LIST DEVICE # VALUE DESCRIPTION TABLE 2. SUGGESTED INPUT VOLTAGE AND POWER SUPPLY LIMITS GAIN SUGGESTED VIN LIMIT OVERLOAD VIN LIMIT SUGGESTED SUPPLY VOLTAGE C1-C5 0.01µF Decoupling Capacitors C6 Open Optional Output Filter Capacitor 0.25 ±10V ±12V ±15V C7 Open Optional Input Filter Capacitor 10 ±1V ±1.2V ±15V 1.2pF Input Filter Capacitor (G = 0.25) 100 ±0.1V ±0.12V ±15V D1, D2 S1A Reverse Power Protection R1 30kΩ Feedback Gain Resistor (G = 0.25) 120kΩ Feedback Gain Resistor (G = 10, 100) 120kΩ Input Gain Resistor (G = 0.25) 12kΩ Input Gain Resistor (G = 10) 1.2kΩ Input Gain Resistor (G = 100) R3, R5, R7 0Ω User Selectable Resistors R8, R9 0Ω Optional Output Filter Resistors R10, R11 0Ω Optional Input Filter Resistors 49.9kΩ Input Filter Resistors (G = 0.25) R4, R6 1MΩ Ground Input for Stability U1 ISL28617 TSSOP 24-Pin Package R2 TABLE 3. ORDERING INFORMATION BOARD PART NUMBER GAIN TYPE ISL28617VY25EV1Z 0.25 Eval Board ISL28617VY10EV1Z 10 Eval Board ISL28617VY100EV1Z 100 Eval Board ISL28617VYXXEV1Z Evaluation Board Layout FIGURE 1. TOP LAYER 2 FIGURE 2. BOTTOM LAYER AN1753.2 September 26, 2012 Application Note 1753 ISL28617VYXXEV1Z Evaluation Board Layout (Continued) FIGURE 3. ASSEMBLY DRAWING ISL28617VYXXEV1Z Schematic IN- IN+ -VFB +VOUT -VOUT 1MΩ 0Ω R6 R11 (NOTE) 0Ω R10 (NOTE) TP9 TP6 15 14 VEO 13 VEE C5 +VFB VREF TP10 D2 VEO 0.01µF VCO 16 0Ω VEE 0Ω C4 VCC R7 0.01µF 19 12kΩ -RIN SENSE 0Ω 0.01µF R8 -RFB SENSE 20 VCMO 17 12 C2 0Ω 0.01µF R3 C1 D1 +RFB SENSE +RIN SENSE 21 8 GND 11 VCO +RIN -RIN 18 10 TP2 +RFB OPEN 22 7 -R FB 9 TP1 DNC R9 VCC DNC C7 (NOTE) 23 R5 6 IN- 24 R2 (NOTE) 5 120kΩ R1 (NOTE) 4 IN+ TP8 0.01µF 3 DNC U1 ISL28617 24 LD TSSOP C3 2 NC 0Ω 1 1MΩ R4 TP7 C6 OPEN VOUT+ GND TP3 TP4 VOUT- NOTE: COMPONENT VALUES FOR AV = 10 BOARD ONLY. SEE TABLE 1 FOR VALUES USED ON AV = 0.25 AND AV = 100 BOARDS. TP5 FIGURE 4. ISL28617VY10EV1Z (AV = 10) EVALUATION BOARD SCHEMATIC 3 AN1753.2 September 26, 2012 Application Note 1753 TABLE 4. BILL OF MATERIALS FOR AV = 10 BOARD (ISL28617VY10EV1Z) PART # REF DES QTY DESCRIPTION MANUFACTURER GRM39X7R103K050 C1-C5 5 CAP, SMD, 0603, 0.01µF, 50V, 10%, X7R, Murata ROHS DNP C6, C7 0 DO NOT POPULATE 5000 TP1, TP9 2 CONN-MINI TEST POINT, VERTICAL, RED, Keystone ROHS 5001 TP4 1 CONN-MINI TEST POINT, VERTICAL, BLK, ROHS Keystone 5002 TP7, TP8 2 CONN-MINI TEST POINT, VERTICAL, WHITE, ROHS Keystone 5004 TP3, TP5 2 CONN-MINI TEST POINT, VERTICAL, YEL, ROHS Keystone S1A D1, D2 2 DIODE-RECTIFIER, SMD, 2P, SMA, 50V, 1A, 1.4W, ROHS Fairchild ISL28617FVZ U1 1 IC-40V R/R OUTPUT ADC DRIVER, 24P, TSSOP, 4X5, ROHS Intersil ERJ-3GEY0R00V R3, R5, R7-R11 7 RES, SMD, 0603, 0Ω, 1/10W, TF, ROHS Panasonic ERJ-3EKF1004V R4, R6 2 RES, SMD, 0603, 1M, 1/10W, 1%, TF, ROHS Panasonic Y4027120K000B9W R1 1 RES-Z1 PRECISION, SMD, 2515, 120k, 3/4W, 0.1%, FOIL, ROHS Vishay Y402712K0000B9W R2 1 RES-Z1 PRECISION, SMD, 2515, 12k, 3/4W, 0.1%, FOIL, ROHS Vishay DNP TP2, TP6, TP10 0 DO NOT POPULATE 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 AN1753.2 September 26, 2012