r.analog WDEVICES Rugged, Military Temperature Range, 10 khz Bandwidth Isolation Amplifier AD203SN FUNCTIONAL BLOCK DIAGRAM

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1 r.analog WDEVCES FEATURES Rugged Design: C Environmental Test Methods 14 (Moisture Resistance) 11 Condition B (Temperature Cycling, -55 C to +125 C) 22 Condition B (Mechanical Shock@ 1,5 g for.5 ms) 24 (Lead ntegrity) 27 Condition A (Variable Frequency 215 (Resistance to Solvents) Reliable Design: Conforms to Stringent Quality and Reliability Standards Characterized to the Full Military Temperature Range -55 C to +125 C Rated Performance 1 khz Full Poer Bandidth Lo Nonlinearity: ±.25% max Wide Output Range: ±1 V min (nto a 2.5 k!l Load) High CMV solation: 15 V RMS Continuous solated Poer: ±15 V DC@ ±5 ma Small Size: 2.23"x.83"x.65" 56.6 mmx21.1 mmx16.5 mm Uncommitted nput Amplifier To-Port solation Through Transformer Coupling SOLATON AMPLFERS Provide Galvanic solation Beteen the nput and Output Stages Eliminate Ground Loops Reject High Common Mode Voltages and Noise Protect Sensitive Electronic Signal Processing Systems from Transient and/or Fault Voltages APPLCATONS NCLUDE Engine Monitoring and Control Mobile Multichannel Data Acquisition Systems nstrumentation and/or Control Signal solation Current Shunt Measurements High Voltage nstrumentation Amplifier GENERAL DESCRPTON The AD23SN is designed and built expressly for use in hostile operating environments. The AD23SN is also an integral member of Analog Devices' AD2 Series of lo cost, high performance, transformer coupled isolation amplifiers. Technological innovations in circuit design, transformer construction, surface mount components and assembly automation have resulted in a rugged, economical, military temperature range isolator that either retains or improves upon the key performance specifications of the AD22/AD24 line. Rugged, Military Temperature Range, 1 khz Bandidth solation Amplifier AD23SN FUNCTONAL BLOCK DAGRAM MODULATOR ' DEMODULATOR NPUT PORT OUTPUT PORT The AD23SN provides total galvanic isolation beteen the input and output stages of the isolation amplifier, including the poer supplies, through the use of internal transformer coupling. The functionally complete design of the AD23SN, poered by a single + 15 V de supply, eliminates the need for an external de/de converter. This permits the designer to minimize the necessary circuit overhead and consequently reduce the overall design and component costs. Furthermore, the poer consumption, nonlinearity and drift characteristics of transformer coupled devices are vastly superior to those achievable ith other isolation technologies, ithout sacrificing bandidth or noise performance. Finally, the AD23SN ill maintain its high operating performance even under sustained common mode stress. The design of the AD23SN emphasizes maximum flexibility and ease of use in a broad range of applications here signals must be measured or transmitted under high CMV conditions. The AD23SN has a ± 1 V output range, an uncommitted input amplifier, an output buffer, a 1 khz full poer bandidth and a front-end isolated poer supply of ± 15 V de (CT; ± 5 ma.

2 - AD23SN-SPECFCAJQNS +25 C, Vs= +15 V de iless GAN Range 1 VN-1 VN Error ±1% typ (±4% max) vs. Temperature 1-55 C to C 5 ppm/ C -55 C to +25 C 1 ppm/ C -4 C to + 25 C 8 ppm/ C - 25 C to + 25 C 6 ppm/ C + 25 C to C 5 ppm/ C vs. Time ± 5 ppm/1 hours vs. Supply Voltage ±.5%N Nonlinearity 2, G= 1 VN, ±1 V Output Sing ±.12% (±.25% max) NPUT VOLTAGE RATNGS Linear Differential Range Max CMV nput to Output AC, 6 Hz, Continuous Continuous (ac and de) Common Mode Rejection 6 Hz Rs '.'S 1!1 (H & LO nputs), G = 1 VN G = 1 VN Rs '.'S 1 k!1 (nput, H, LO or Both), G = 1-1 VN Leakage Current, nput to Output@ 24 V rms, 6 Hz NPUT MPEDANCE Differential (G = 1 VN) Common Mode NPUT BAS CURRENT + 25 C C NPUT DFFERENCE CURRENT + 25 C C NPUT NOSE Voltage,.1 Hz to 1 Hz Voltage, Frequency> 2 Hz ±lov 15 V rms ±2 V peak 16dB 12dB 96dB (min) 4.µA rms (max) 112 n 2 G!1ll4.5 pf 3 pa 3 na ±5 pa ±5 na 4 µv p-p 5 nv/vhz FREQUENCY RESPONSE Bandidth (VoUT '.'S 2 V p--p, G = 1-1 VN) 1 khz Sle Rate.5 V/µs Settling Time to ±.1% 16 µs OFFSET VOLTAGE, REFERRED TO NPUT (RT) + 25 C (Adjustable to Zero) vs. Temperature (-55 C to C) ± (5 + 25/G) mv (max) ± (6 + 1/G) µvl C RATED OUTPUT 3 Voltage (Out H to Out RL = 5. k!1 ±1 V (min) Current ±4mA Maximum Capacitive Load 4 27 pf Output Resistance.2 n Output Ripple, 1 khz Bandidth 15 mv p-p 5 khz Bandidth.7 mv rms SOLATED POWER OUTPUT 5 Voltage, No Load ±15 v Accuracy ±5% Current (Either Output) 5mA Reulation, No Load to Full Load 5% Ripple, 1 khz Bandidth, Full Load llo mv p--p POWER SUPPLY. Voltage, Rated Performance + 15 V de (±5%) Voltage, Operating Performance V de to + 16 V de Current, No Load (Vs= +15 V de) 2mA,! otherise noted) -2-

3 AD23SN TEMPERATURE RANGE Rated Performance Storage PACKAGE DMENSONS nches Millimeters -55 C to C - 55 C to C 2.23 x.83 x X 21.l X 16 5 NOTES 'Refer to Figure 1 for a plot of gain versus temperature. 2 For gains greater than 5 VN, a 1 pf capacitor from the feedback terminal of the input op amp (Pin 38) to the input common terminal (Pin 2) is recommended in order to minimize the gain nonlinearity. Refer to Figure 17 for a circuit schematic. 3 For additional information on the Rated Output parameters, refer to Figure 9 for a plot of the Output Voltage Sing vs. Poer Supply Voltage, and Figure 1 for the Output Current vs. Temperature and Poer Supply Voltage relationship. For larger capacitive loads, it is recommended that a 4. 7 fl resistor be placed in series ith the load in order to suppress possible output oscillations. ' LO µf (min) decoupling is required. 6 Refer to Figure 9 for a plot of output voltage sing versus supply voltage. Specifications subject to change ithout notice. AC162 MATNG SOCKET ',... :::: :: 1 l +--'-- olo= -=--=---=--'--olo-o-:- T ! !-J:_ J(21.).125 TYP (2.5) DA. C/S TO l 3 2l.18 (4.6) DA. TYP 2 PLACES AD23SN PN DESGNATONS PN DESGNATON FUNCTON 1 N+ NPUT OP AMP: NONNVERTNG NPUT 2 NCOM NPUT COMMON 3 N- NPUT OP AMP: NVERTNG NPUT 18 OUT RTN OUTPUT RETURN 19 OUTH OUTPUT SGNAL 2 PWRN DC POWER SUPPLY NPUT 21 NONE NONE 22 PWRCOM DC POWER SUPPLY COMMON 36 V;so+ SOLATED POWER: + DC 37 VSO- SOLATED POWER: - DC 38 FB NPUT OP AMP: OUTPUT/FEEDBACK PORT NPUT NPUT NPUT OUTPUT OUTPUT OUTPUT ŌUTPUT NPUT NPUT NPUT CONTROLLNG DMENSONS ARE N NCHES, MLLMETER DMENSONS ARE CONVERTED EQUVALENTS AND SHOULD NOT BE USED FOR DESGN. CAUTON ESD (electrostatic discharge) sens1uve device. Permanent damage may occur on unconnected devices subject to high energy electrostatic fields. Unused devices must be discharged to the destination socket before devices are removed. Note: Per ML-STD-883C, Method 315, this device have been classified as a Category 2 ESD sensitive device. WARNNG! ENS l llvl UtV Cl -3-

4 AD23SN PRODUCT HGHLGHTS Rugged Design. The AD23SN is specifically designed for applications here ruggedness and high performance are the key requirements. The ruggedness of the AD23SN design meets ML-STD-883C Methods 14 (Moisture Resistance), 11 Condition B (Temperature Cycling, -SS C to C), 22 Condition B (Mechanical 1,5 g for.5 ms), 24 (Lead ntegrity), 27 Condition A (Variable Frequency 2 g) and 215 (Resistance to Solvents). Engine and vehicular monitor/control systems as ell as mobile instrumentation and control systems are some examples of applications for hich the AD23SN is ell suited. Military Temperature Range Rating. With its performance rated over the -SS C to C ML specification temperature range, the AD23SN is an excellent choice in applications here severe environmental conditions may be encountered. Examples include engine monitoring/control systems and remote poer line monitoring. 1 khz Bandidth. With a full poer bandidth of 1 khz, the AD23SN is effective in control loop applications here a smaller bandidth could induce control system instabilities. Excellent Common Mode Performance. The AD23SN provides a 1.5 kv rms continuous common mode isolation. A lo common mode input capacitance of 4.5 pf, inclusive of poer isolation, results in a minimum 96 db of CMR as ell as a very lo leakage current of 4. µa rms 24 V rms, 6 Hz). High Accuracy. Exhibiting a maximum nonlinearity of ±.25% and a lo gain temperature coefficient, averaging SO ppm/ C over the full temperature range, the AD23SN provides high isolation ithout loss of signal integrity and quality. solated Poer. An isolated poer supply capable of delivering ± 15 V ± 5 ma is available at the input port of the isolator. This permits the AD23SN to poer up floating signal conditioners, front-end amplifiers or remote transducers at the input. Flexible nput Stage. An uncommitted op amp is provided on the input stage. This amplifier provides input buffering and gain as needed. t also facilitates a host of alternative input functions including filtering, summing, high voltage ranges and current (transimpedance) inputs. DESCRPTON OF KEY SPECFCATONS Gain Nonlinearity. Nonlinearity is defined as the peak deviation of the output voltage from the best straight line and is expressed as a percent of peak-to-peak output voltage span. The nonlinearity of the model AD23SN, hich operates at a 2 V p-p output span, is ±.25% or ±5 mv. Good nonlinearity is critical for retaining signal fidelity. Max CMV, nput to Output. Maximum common mode voltage (CMV) describes the amount of voltage that may be applied across both input terminals ith respect to the output terminals ithout degrading the integrity of the isolation barrier. High input-to-output CMV capability is necessary in applications here high CMV inputs exist or high voltage transients may occur at the input. Common Mode Rejection (CMR). CMR describes the isolator's ability to reject common mode voltages that may exist beteen the inputs and the outputs. High CMR is required hen it is necessary to process small signals riding on high common mode voltages. Leakage Current. This is the current that flos from the input common across the isolation barrier to the output common hen the poer-line voltage (either 115 V or 24 V rms, 6 Hz) is impressed on the inputs. Leakage current is dependent on the magnitude of the coupling capacitance beteen the input and the output ports. Line frequency leakage current levels are unaffected by the poer ON or OFF condition of the AD23SN. Common Mode nput mpedance. This is defined to be the impedance seen across either input terminal (i.e., +N or - N) and the input common. nput Noise. This specification characterizes the voltage noise levels that are generated internally by the isolation amplifier. n order to facilitate a comparison beteen the "isolator background noise" levels and the expected input signal levels the input noise parameter is referred to the input. nput noise is a function of the noise bandidth, i.e., the frequency range over hich the noise characteristics are measured. Offset Voltage, Referred to nput (RT). The offset voltage describes the isolation amplifier's total de offset voltage ith the inputs grounded. The offset voltage is referred to the input in order to allo for a comparison of the de offset voltages ith the expected input signal levels. The total offset comes from to sources, namely from the input and output stages, and is gain dependent. To compute the offset voltage, RT, the isolator is modelled as to cascaded amplifier stages. The input stage has a variable gain G hile the output isolation stage has a fixed gain of 1. RT offset is then given by: here: E 5 (RT!) = E 51 + E 5 ig E 81 = Total input stage offset voltage E s 2 = Output stage offset voltage G = nput stage gain. Offset voltage drift, RT, is calculated in an identical manner. solated Poer Output. Dual supply voltages, completely isolated from the input poer supply terminals, provide the capability to excite floating input signal conditioners as ell as remote transducers. -4-

5 AD23SN PERFORMANCE CHARACTERSTCS This section details the key specifications of the AD23SN that exhibit a functional dependence on such variables as frequency, poer supply load, output voltage sing, bypass capacitance and temperature. Table summarizes the performance characteristics that ill be discussed in this section. For the sake of completeness, a typical dynamic output response of the AD23SN is included. Gain Temperature Coefficient. Figure 1 presents the AD23SN's gain temperature coefficient over the entire -55 C to C temperature range. Gain Nonlinearity. The maximum nonlinearity error of the AD23SN, at a gain of 1 VV, is specified as ±.25% or ± 5 m V. The nonlinearity performance of the AD23SN is dependent on the output voltage sing and this dependency is illustrated in Figure 2. The horizontal axis represents the gain error, expressed either in percent of peak-to-peak output span (i.e., % of 2 V) on the left axis or in mv on the right axis. The vertical axis indicates the magnitude of the output voltage sing..5k -1k / " -2k E -3k c. c. -4k 2 <i (!) -5k -6k -7k -Bk TEMPERATURE - "C Figure 1. Gain {ppm of Span) vs. Temperature ( C) +.2 #. +.1 a: OUTPUT VOLTAGE SWNG -V Figure 2. Gain Nonlinearity Error (% p-p Output Range and mv) vs. Output Voltage Sing (V), ith a Gain of 1 VV > E a: a: a: Note: 1 ppm (part per million) is equivalent to.1 %. Parameter Gain nput Voltage Rating nput Noise Frequency Response Key Specifications Gain (ppm of Span) Gain Nonlinearity (Expressed in mv and % of p-p Output) Common Mode Rejection (db) nput Noise (nv/vhz) As a Function of Shon n Temperature ( C) Figure 1 Output Voltage Sing (V) Figure 2 Common Mode Signal Frequency Figure 3 (Hz), Amplifier Gain (VV) and nput Source Resistance (!1) Frequency (Hz) Figure 4 Frequency Response: Gain (db) Frequency (Hz) Figure 5 Frequency Response: Phase Shift (Degree) Frequency (Hz) Figure 6 Dynamic Response NA Figure 7 Offset Output Offset Voltage (mv) Temperature ( C) Figure 8 Rated Out Output Voltage Sing (V) Supply Voltage (V de) Figure 9 Output Current (ma) Supply Voltage (V de) Figure 1 solated Poer Supply solated Poer Supply Voltage (V) Current Delivered to the Load (ma) Figure 11 solated Poer Supply Ripple (m V p-p) Current Delivered to the Load (ma) Figure 12 solated Poer Supply Ripple (V p-p) Bypass Capacitance (µf) Figure 13 Table. Performance Characteristics Detailed in the AD23SN Data Sheet -5-

6 AD23SN Common Mode Rejection. Figure 3 illustrates the common mode rejection (CMR), expressed in db, of the AD23SN versus frequency (Hz), gain (VV) and source impedance imbalance (D). To achieve the optimal common mode rejection of unanted signals, it is recommended that the source imbalance be kept as lo as possible and that the input circuitry be carefully laid out so as to avoid adding excessive stray capacitances at the isolator's input terminals..,, 14 "' <..>..., 1 a: 9 Q :;; :;; :;; 6 <..> 5 4 ' -, '-. '-, - "'r-. llso"'" ,,, " -...: lisso;..._ r "1ok " *... r G=1 --G=1..._ _ FREQUENCY - Hz Figure 3. Common Mode Rejection (CMR) vs. Frequency (Hz), Gain (VN) and Resistance {[}) nput Noise. Figure 4 presents the typical input noise characteristics, in nv/vhz, of the AD23SN for a frequency range from 1 Hz to 1 khz G=1V/V G=1V/V 1k FREQUENCY - Hz '" 1k. ' Figure 5. Gain (db) as a Function of Frequency (Hz) -3-6 * m -15,_!:!: -18 :i: -21 CJ) :i: k PHASE G=1 VV PHASE G=1V/V r 5 1k 1k 5k FREQUENCY - Hz > c 1 t!j ;:: cl > CJ) i5 2,_ 1 ::.... '..... _ Figure 6. Phase Shift (.1 ) as a Function of Frequency {Hz) Dynamic Response of the AD23SN. To illustrate the speed, dynamic range and rapid settling time of the AD23SN, the isolator's output response to a 2 V p-p step function is shon in Figure k 1k 1k FREQUENCY - Hz Figure 4. nput Noise (nvl!hz) vs. Frequency (Hz) Frequency Response: Gain and Phase Shift. Figure 5 illustrates the AD23SN's gain as a function of frequency hile Figure 6 illustrates the corresponding phase shift vs. frequency. The AD23SN's lo phase shift and 1 khz bandidth performance make it ideal in poer monitoring and control system applications. Figure 7. Dynamic Response of the AD23SN (2 V p-p Step} -6-

7 AD23SN Output Offset Voltage. The AD23SN exhibits a lo output offset voltage temperature coefficient over the + 25 C to C temperature range as shon in Figure 8. > E 2,_ ff -2,_ :> -4 :> i' ' ' TEMPERATURE - C Figure 8. Output Offset Voltage rmv) vs. Temperature r C) ith G=1 VN Rated Output. The rated output voltage, across the OUT H and OUT LO terminals, for the AD23SN is specified at ±O V. This specification applies hen the AD23SN is poered by a + 15 V de supply. The rated output voltage level is, hoever, affected by the input poer supply voltage and the loads placed on the isolated poer supply. This dependency is illustrated in Figure 9. The current delivered by the output terminals of the AD23SN ill vary as a function of the supply voltage and operating temperature. These relationships are illustrated in Figure O. solated Poer. The load characteristics of the AD23SN's isolated poer supplies (i.e., + 15 V de and -15 V de) are plotted in Figure 11. The isolated poer supply exhibits some ripple hich varies as a function of the load current. Figure 12 demonstrates this relationship. The AD23SN has internal bypass capacitors that optimize the tradeoff beteen output ripple and poer supply performance, even under full load. f a specific application requires more bypassing on the isolated poer supplies, external capacitors may be added. Figure 13 plots the isolated poer supply ripple as a function of external bypass capacitance under full load conditions (i.e., 5 ma). 12 > ti (!) z ii: 1 "' 9,_ > 8 :>. 5 7 v / / =+1V v / / / V =-1V v..,,,.., t.> ± =F"""' > ± t '.'.;.. :> "' a: ± t.,_ fil :5 '!? SUPPLY VOLTAGE - V DC Figure 9. Output Voltage Sing r±v) vs. Poer Supply nput Voltage (V DC), ith a 2.5 kn Load ±1 ±5 ±1 ±15 LOAD - ma Figure 11. solated Poer Supply Voltage (V DC) vs. Load rma) V =+1 V -55 C TO +125 C j,_ i'e a: a: j :> t.> j e: V =-1 V i j > ii: 3-+--i""'-"--t----t :> "' a: :;;: '!? -5L L :::::,,,,,_, SUPPLY VOLTAGE-V DC Figure 1. Output Current rma) vs. Supply Voltage (V DC) and Temperature r C), ith V 15 Loaded at 5 ma LOAD- ma 1 11 Figure 12. solated Poer Supply Ripple rmv p-p) vs. Load rma).j'

8 AD23SN 1 > E 2. 9: 1 "' '.'.; it "' 2 1 c 1..._ """ 'r--.r-. "r--..._.1 1 BYPASS CAPACTANCE - µf Figure 13. solated Poer Supply Ripple (mv p-p} vs. Bypass Capacitance (µf), ith a 5 ma Load on ± V 15, and Noise Bandidth of 1 MHz. The curves in Figures 12 and 13 ere generated by measuring the poer supply ripple over a 1 MHz bandidth. CAUTON: The AD23SN does not provide for short circuit protection of its isolated poer supply. A current limiting resistor may be placed in series ith the isolated poer terminals and the load in order to protect the supply against inadvertent shorts. APPLCABLE STANDARDS The tests and methods employed in the design verification process are summarized in Table. A copy of the AD23SN Quality & Reliability Summaries test report, hich documents the results of the tests listed in Table, is available on request. 1 NSDE THE AD23SN The functional block diagram of the AD23SN is shon in Figure 14. The AD23SN employs amplitude modulation techniques to implement transformer coupling of signals don to de. The 35 khz, 3 V p-p square ave carrier used by the AD23SN is generated by an internal oscillator located in the output port of the isolator. This oscillator is poered by a + 15 V de supply. A full ave modulator translates the input signal to the carrier frequency hich is then transmitted across transformer Tl. The synchronous demodulator in the output port extracts the input signal from the carrier. The 12 khz to-pole filter is employed to minimize output noise and ripple. Furthermore, the filter serves as a lo impedance output buffer. The input port of the AD23SN contains an uncommitted input op amp, a modulator and the poer transformer T2. The primary of the poer transformer is driven by the 35 khz square ave hile the secondary, in conjunction ith a rectifier netork, supplies isolated poer to the modulator, input op amp and any external load. The uncommitted input amplifier can be used to supply gain or to buffer the input signals. MODULATOR T1 '. ' POWER '' -. ll 35kHz DEMODULATOR OSCLLATOR AD23SN 12 khz LP FLTER & OUTPUT BUFFER t i Test Method ML-STD-883C, Method 14 ML-STD-883C, Method 11 Condition B ML-STD-883C, Method 22, Condition B ML-STD-883C, Method 23 ML-STD-883C, Method 24 ML-STD-883C, Method 27, Condition A ML-STD-883C, Method 215 ML-STD-883C, Method Analog Devices Product Reliability Program Test Description Moisture Resistance Temperature Cycling, - 55 C to C Mechanical Shock@ 1,5 g for.5 ms Solderability of Terminations ntegrity of Microelectronic Device Leads Variable Frequency g Resistance to Solvents Electrostatic Discharge Sensitivity Classification MTBF Calculation (per ML-HDBK-217D) and Verification ' NPUT PORT OUTPUT PORT Figure 14. Functional Block Diagram USNG THE AD23SN Poering the AD23SN. The AD23SN requires only a single + 15 V de poer supply connected as shon in Figure 15. A bypass capacitor is provided in the module. PWRN +12VDCTO +16 V DC SUPPLY PWRCOM SUPPLY COMMON Figure 15. Poering the AD23SN Unity Gain nput Configuration. The basic unity gain configuration for input signals of up to ± 1 V is shon in Figure 16. Table. Tests Used to Verify the Ruggedness, Reliability and Quality of the AD23SN Design Per 883C Method 315.5, the AD23SN has been classified as a Class 2 ESD (electrostatic discharge) sensitive device. As a Class 2 device, the AD23SN is insensitive to static discharge voltages of less than 2 V. Vs1GNAL (±1V) -8- Figure 16. Basic Unity Gain Configuration

9 AD23SN nput Configuration for a Gain Greater Than (G > 1). When small input signal levels must be amplified and isolated, Figure 17 shos ho to get a gain greater than 1 hile continuing to preserve a very high input impedance. n this circuit, the gain equation may be ritten as: nverting, Summing or Current nput Configuration. Figure 19 shos ho the AD23SN can accommodate current inputs or sum currents or voltages. here V Output Voltage (V) V srg nput Signal Voltage (V) RF Feedback Resistor Value (!1) RG = Gain Resistor Value (!1). Note on the 1 pf Capacitor. Whenever a gain of 5 VV or greater is required, a 1 pf capacitor from the FB (input op amp feedback) terminal to the N COM (input common) terminal, as shon ith the dotted lines in Figure 17, is highly recommended. The capacitor acts to filter out sitching noise and ill minimize the isolator's nonlinearity parameter. Figure 17. nput Configuration for a Gain Greater than 1 Compensating the Uncommitted nput Op Amp. The open loop gain and phase versus frequency for the uncommitted input op amp are given in Figure 18. These curves are to be used to determine the appropriate values for the feedback resistor and compensation capacitor in order to ensure frequency stability hen a gain greater than unity is required. The final values for these components should also be chosen so as to satisfy the folloing constraints: The current dran in the feedback resistor (Rp) is no greater than 1 ma. The feedback (Rp) and gain resistor (RG) result in the desired amplifier gain ', ,, "' ;; " " g : " :; ii: lk 1k 1k 1M lom FREQUENCY - Hz Figure 18. Open Loop Gain and Phase vs. Frequency for the Uncommitted nput Op Amp " Figure 19. nput Configuration for Summing or Current nput n this circuit the output voltage equation can be ritten as: here Vo= -Rpx(s+Vs1!Rs1+Vs2!Rs2+... ) V Output Voltage (V) V si Voltage of nput Signal 1 (V) V sz Voltage of nput Signal 2 (V) s nput Current Source (A) RF Feedback Resistor Value (!1) Source Resistance Associated ith nput Rs 1 Signal 1 (!1) Source Resistance Associated ith nput Rs 2 Signal 2 (!1). The circuit of Figure 19 can also be used hen the input signal is larger than the ± 1 V input range of the isolator. For example, suppose that in Figure 19 only V s 1, Rs 1 and RF are connected to the feedback, input and common terminals as shon by the solid lines in Figure 19. No, a Vs 1 ith a ±1 V span can be accommodated ith Rp = 2 k!1 and a total Rs 1 =2 k!1. GAN AND OFFSET ADJUSTMENTS General Comments. When gain and offset adjustments are required, the actual compensation circuit ultimately utilized ill depend on: The input configuration mode of the isolation amplifier (i.e., noninverting or inverting). The placement of the adjusting potentiometer (i.e., on the isolator's input or output side). As a general rule: Offset adjustments are best accomplished on the isolator's input side, as it is much easier and more efficient to null the offset ahead of any gain. Gain adjustments are mostly easily accomplished as part of the gain-setting resistor netork at the isolator's input side. nput adjustments, of the offset and/or gain, are preferred hen the adjusting potentiometers are as near as possible to the input end of the isolator (so as to minimize strays). Output side adjustments may be necessary under the conditions here adjusting potentiometers placed on the input side ould present a hazard to the user due to the presence of high common mode voltages during the adjustment procedure. -9-

10 AD23SN t is recommended that the offset adjustment precedes the gain adjustment. Adjustments for the Noninverting Mode of Operation Offset Adjustment. Figure 2 shos the suggested input adjustment connections hen the isolator's input amplifier is configured for the noninverting mode of operation. The offset adjustment circuit injects a small voltage in series ith the lo side of the signal source. The adjustment potentiometer Pl modulates the injection voltage and is therefore responsible for nulling out the offset voltage. Note: To minimize CMR degradation it is recommended that the resistor in series ith the input LO (i.e., Re) be belo a fe hundred ohms. The offset adjustment circuit of Figure 2 ill not ork if the signal source has another current path to input common, or if current flos in the signal source LO lead. f this is the case, use the output adjustment procedure. Gain Adjustment. Figure 2 also shos the suggested gain adjustment circuit. Note that the gain adjustment potentiometer P2 is incorporated into the gain-setting resistor netork at the isolator's input. GAN ADJUST ured for the inverting mode of operation. Here the offset adjustment potentiometer Pl nulls the voltage at the summing node. This method is preferred over current injection since it is less affected by any subsequent gain adjustments. Gain Adjustment. Figure 21 also shos the suggested gain adjustment circuit. n this circuit, the gain adjustment is made in the feedback loop using potentiometer P2. The adjustments ill be effective for all gains in the 1 to 1 VN range. Output Adjustments Offset Adjustment. Figure 22 shos the recommended technique for offset adjustment at the output. n this circuit, the ± 15 V de voltage is supplied by an independent source. With reference to the output circuitry shon in Figure 22, the maximum offset adjustment range is given by: RDxVs EoFFSET = RD+ Ro here, Vs is the poer supply voltage. A 2 kf! potentiometer (P ) should ork ell in this adjustment circuit. OUTH +15V t ADJUST ZERO Po Ro -15V OUT ATN PWRN (+12V TO +16V DC) PWRCOM Figure 22. Output Side Offset Adjustment Circuit Figure 2. nput Adjustments for the Noninverting Mode of Operation An RGA of 47.5 kf! and a 5 kf! potentiometer, resulting in a median RF value of 5 kf! (i.e., RGA + P2/2), ill ork nicely for gains of 1 VN or greater. The gain adjustment becomes less effective at loer gains, in fact it is halved at G=2 VN, so that potentiometer P2 ill have to be a larger fraction of the total Rp. At a gain of 1 VN attempting to adjust the gain donards ill compromise the isolator's input impedance. n this case it ould be better to adjust the gain at the signal source or after the output. nput Adjustments for the nverting Mode of Operation Offset Adjustment. Figure 21 shos the suggested input adjustment connections hen the isolator's input amplifier is config- GAN ADJUST Figure 21. nput Adjustments for the nverting Mode of Operation Gain Adjustment. Since the AD23SN's output amplifier is fixed at unity, any desired output gain adjustments can only be made in a subsequent stage. USNG SOLATED POWER The AD23SN provides ± 15 V de poer outputs referred to the input common. These may be used to poer various accessory circuits hich must operate at the input common mode level. The input offset adjustment circuits of the previous section are examples of this need. The isolated poer supply output has a current capacity of 5 ma hich should be sufficient to operate adjustment circuits, references, op amps, signal conditioners and remote transducers. CAUTON: The AD23SN does not provide for short circuit protection of its isolated poer supply. A current limiting resistor may be placed in series ith the isolated poer terminals and the load in order to protect the supply against inadvertent shorts. APPLCATONS EXAMPLES solated Process Current to Voltage Converter Figure 23 shos ho the AD23SN can be utilized as an isolated receiver that translates a 4-2 ma process current signal input into a to + 1 V output. The 25 n shunt resistor converts the 4-2 ma current into a + 1 to +5 mv signal. The signal is then offset by - 1 m V via the use of P to produce a to +4 mv input. The signal is then amplified by a gain of 25 resulting in the desired to + 1 V output. With an open circuit on the input side, the AD23SN ill have V on the output, corresponding to the -1 mv offset voltage multiplied by a gain of 25 VN. -1-

11 AD23SN Lo Level nputs n applications here lo level signals need to be isolated (thermocouples are one such application), a lo drift input amplifier can be used ith the AD23SN. Figure 25 illustrates this implementation of the AD23SN. The circuit design also includes a three-pole active filter hich provides for enhanced common mode rejection at 6 Hz and normal mode rejection of frequencies above a fe Hz. f any offset adjustments are desired, they are best done at the trim pins of the lo drift input amplifier. Gain adjustments can be done at the feedback resistor. Figure 23. Using the AD23SN as an solated Process Current to Voltage Converter For the circuit of Figure 23, the input to output transfer function can be expressed as: here VouT rn Vour = 625 xjjn-2.5 V Output Voltage (V) nput Current in milliamps (ma). This current is limited to the 4 to 2 ma range. Current Shunt Measurements n addition to isolating and converting process current signals into voltage signals, the AD23SN can be used to indicate the value of any loop current in general. Figure 24 illustrates a typical current shunt measurement application of the AD23SN. A small sensing resistor RsHUND placed in series ith the current 1oop, develops a small differential voltage that may be further scaled to provide an isolator output voltage that is directly pro-. portional to the current. The voltage developed across the shunt can potentially be several hundred to a thousand volts above ground. n this circuit, the AD23SN provides the necessary scaling of the shunt signal hile providing high common-mode voltage isolation and high common mode rejection of de and 6 Hz components. t VouT {±1V) PWRN Figure 25. Using the AD23SN ith Lo Level nputs The input-output relationship for the circuit shon in Figure 25 can be ritten as: here VouT VrN RG Vour = VNx (1 +SO kwrg) Output Voltage (V) Lo Level nput Voltage (V) solation Amplifier Gain Resistance (D). Noise Reduction in Data Acquisition Systems The AD23SN uses amplitude modulation techniques ith a 35 khz carrier to pass both ac and de signals across the isolation barrier. Some of the carrier's harmonics are unavoidably passed through to the isolator output in the form of ripple. n most cases, this noise source is insignificant hen compared to the measured signal. Hoever, in some applications, particularly hen a fast AD converter is used folloing the isolator, it may be desirable to add filtering at the isolator's output in order to reduce the carrier ripple. Figure 26 shos a circuit that ill reduce the carrier ripple through the use of a to-pole output filter. Figure 24. Using the AD23SN for Current Shunt Measurements The transfer function for the circuit of Figure 24 can be ritten as: here VouT Rs HUNT RF RG LOOP VouT = RsHuNrx(+Rp/RG)xloP Output Voltage (V) Sense or Current Shunt Resistance (D) Feedback Resistance (D) Gain Resistance (D) Loop Current (A). Figure 26. Noise Reduction in Data Acquisition Systems Using the AD23SN -11-

12 SELECTON GUDE FOR ANALOG DEVCES' FAMLY OF SOLATON AMPLFERS... General f You Need: solator for Multichannel Applications Loest Cost solator 3-Port solation Rugged, Military Temperature Range solator Medical solator AD22J AD22K AD23SN AD24J AD24K AD21AN Gain Lo Nonlinearity (""±.1?%) ±.5% ±.25% ±.25% ±.5% ±.25% ±.25% Lo Gain Temp. Co. (""25 ppm/qc) 45 ppm/qc 45 ppm/qc 6 ppm/qc 45 ppm/qc 45 ppm/qc 25 ppm/qc solation High CMV Rating (2:2.5 kv rms, Continuous) 75 V rms 1.5 kv rms 1.5 kv rms 75 V rms 1.5 kv rms 2.5 kv rms High CMR (2:14 db, All Conditions) 1 db 1 db 96 db 14 db 14 db 12 db Lo Leakage Current (""2 µarms, 24 V rms, 6 Hz) 2 µarms 2 µarms 4 µarms 2 µarms 2 µarms 2 µarms Speed 2 khz Full Signal Bandidth 1 khz Full Signal Bandidth 5 khz Full Signal Bandidth 2 khz 2kHz Fast Settling Time (""15 µs) lms lms 15 µs lms lms 15 µs Fast Sle Rate (2:1V/ µs).5 V/ µs 1 V µs Offset Lo Offset Drift Temp. Co. (""2 µv/qc) 2 µv/qc 2 µvl C 55 µvl C 2 µvl C 2 µvl C 4 µv/qc Rated Output ± 1 V Differential Output ±5 v ±5 v ±1 v ±5 v ±5 v ±1 v Lo Output mpedance (""l!1) 7 k.!1 7 k.!1.2!1 3 k!1 3 k!1 1!1 solated Poer solated Front End Poer (2:75 mw) 6mW 6mW 15mW 37.5 mw 37.5 mw 15mW Supply nput Poer Supply solator Poered by a de Supply +15 V de +15 V de + 15 V de 15 v p-p 15 v p-p +15 V 25 khz Rated Performance Temperature -55QC to + 125QC, Rated Range -4QC to +85QC, Rated Range -25QC to +85QC, Rated Range to + 7QC, Rated Range 2 Packaging Small Size (.325 in 3 typ) SP Pkg. SP Pkg in 3 SP Pkg. SP Pkg..735 in 3 SP Package DP Package NOTES All performance specification numbers apply for G=l VN and to +7D C. Quotations for nonlinearity, gain temperature coefficient, CMV rating and leakage current are max numbers; CMR and offset temperature coefficient are min, all other are typical. solated front end poer specifications are for both the + and - terminals. The 284J leakage applies for 115 V rms. 2 The AD22, AD24 and AD21 series ill operate in the -4QC to+85qc temperature range. AD21BN AD21JN 284J ±.12% ±.25% ±.5% 25 ppm/qc 25 ppm/qc 75 ppm/qc 2.5 kv rms 1.5 kv rms 3.5 kv rms 12 db 12 db 78 db 2 µarms 2 µarms 2 µa rms 1 7 Hz 15 µs 15 µs 1 V/ µs 1 V/ µs 25 mv/ µs 4 µv/qc 4 µv/qc 17 µv/qc ±1 v ±1 v ±5 v 1!1 1!1 1 k.!1 15mW 15mW 85mW + 15 V de + 15 V de +15 V de.735 in in in 3 PRNTED N U.S.A. C /89

13 Data Sheet AD23SN OUTLNE DMENSONS 2.23 (56.6) MAX.15 (3.81) MN SDE VEW.65 (16.5) MAX.1 (2.5) TYP.18 (.45) SQ.83 (21.1) MAX BOTTOM VEW (15.2) (5.5) 1.6 (4.6) CONTROLLNG DMENSONS ARE N NCHES; MLLMETER DMENSONS (N PARENTHESES) ARE ROUNDED-OFF NCH EQUVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRATE FOR USE N DESGN. Figure 27. AD23 SP Package (N-11) 11-Lead Count ith 38-Lead Spacing Dimensions shon in inches and (millimeters) 7258-A ORDERNG GUDE Model Temperature Range Package Description Package Option AD23SN 55 C to +125 C 11-Lead SP Package N-11

14 Data Sheet AD23SN REVSON HSTORY 8/216 Rev. A to Changes to Features Section... 1 Deleted Prices Analog Devices, nc. All rights reserved. Trademarks and registered trademarks are the property of their respective oners. D /16(B)