1 application note 1508 ISL281X7SOICEVAL1Z evaluation board user?s guide introduction the ISL281X7SOICEVAL1Z evaluation board is a design platform containing all the circuitry needed to characterize critical performance parameters of the isl281x7 operational amplif iers in soic-8 package, using a variety of user defined test circuits. the isl281x7 operational am plifiers feature low bias current, low noise, and low offset and temperature drift. reference documents ? isl28107 data sheet, fn6631 ? isl28117 data sheet, fn6632 ? isl28127 data sheet, fn6633 evaluation board key features the ISL281X7SOICEVAL1Z is designed to enable the ic to operate from a single su pply, +4.5vdc to +40vdc or from split supplies, 2.25vdc to 20v. 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 and provisions for a user-selectable voltage divider-filter are included. power supplies (figure 1) external power connections are made through the +v, -v, vref 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, +v and -v terminals connect to their respective power supply terminals. de-coupling capacitors c2 and c4 connect close to their respective supplies, while two additional capacitors, c1 and c5, are connected close to the part to filter out high frequency noise. anti-reverse diodes d1 and d2 protect the circuit in the case of accidental polarity reversal. amplifier configuration (figure 2) the schematic of 1/2 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 must be connected to ground to establish a ground referenced input for dual supply operation, or can be externally set to any reference level for single supply operation. vref should not be left floating. c2 4.7f dnp d2 d1 r16 r4 c4 j8 j11 j9 j10 j7 j13 s1ab 4.7f s1ab dnp vref v+ v- figure 1. power supply circuit in- in+ rf vref in - in + gnd 100k rref+ vout isl281x7 vp v- 0 vm vcm in- in+ vref v+ rin- 10k rin+ 10k - + 100k rl dnp figure 2. basic amplifier configuration 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. 2009. all rights reserved all other trademarks mentioned are the property of their respective owners. november 9, 2009 an1508.0
2 an1508.0 november 9, 2009 user-selectable options (figures 3 and 4) component pads are included to enable a variety of user-selectable circuits to be added to the amplifier vref, inputs, outputs, and the amplifier feedback loops. the inputs (figure 3) have additional resistor and capacitor, and jumper placements for loading and/or measurement of frequency sensitive parameters. the outputs (figure 4) have additional resistor and capacitor placements for filtering and loading. 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. figure 3. input stage figure 4. output stage in- out node in+ c3 r7 r5 j2 j1 r1 r6 r14 r2 r14 r3 r15 r10 r8 r11 r9 dnp dnp dnp dnp dnp dnp dnp open dnp dnp 10k 100k 100k 10k 0 vref to output to in+ to in- r13 r12 r18 j12 c6 r17 dnp 0 open table 1. ISL281X7SOICEVAL1Z components parts list device # description comments c2, c4 cap, smd, 0805, 4.7f, 50v, 10%, x7r, rohs power supply decoupling c1, c5 cap, smd, 0603, 0.01f, 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, 40v, 0.5a, rohs reverse power protection u1 (isl28107fbz) op amp, soic, rohs u1 (isl28117fbz) op amp, soic, rohs u1 (isl28127fbz) op amp, soic, rohs r1-r4, r6-r8, r10, r13, r14, r16, r17, r19, r20 resistor, smd, 0603, 0.1%, mf, dnp-place holder user selectable resistors - not populated r5, r18 res, smd, 0603, 0 , 1/10w, tf, rohs zero ohm user selectable resistors r9, r12 res, smd, 0603, 10k, 1/10w, 1%, tf, rohs gain resistors r11, r15 res, smd, 0603, 100k, 1/10w, 1%, tf, rohs gain resistors application note 1508
3 intersil corporation reserves the right to make changes in circui t design, software and/or specifications at any time without n otice. 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 an1508.0 november 9, 2009 application note 1508 figure 5. ISL281X7SOICEVAL1Z top view
4 an1508.0 november 9, 2009 application note 1508 output in + out node in+ in- in - c2 4.7f dnp r20 r19 d2 d1 r18 u1 r16 r4 j4 j6 j5 j3 c3 r7 r5 c4 c1 c5 j12 j2 j1 j8 j11 j9 j10 1 j7 j13 c6 r1 r6 r14 r2 r17 r12 r3 r15 r13 r10 r8 r11 r9 10k dnp 0.01f dnp dnp 0.01f dnp 0 open 100k soic8 dnp dnp dnp dnp dnp dnp open 100k 10k dnp 0 dnp s1ab 4.7f s1ab dnp 5 6 7 8 3 4 1 2 generic pack. vref vref v+ v- figure 6. ISL281X7SOICEVAL1Z schematic diagram
|
