ANALOG DEVICES FEATURES 3-Port Isolation with +2500V CMV 120dB min CMR at 60Hz: Fully Guarded Inputs +10V Input/Output Dynamic Range Gain Adjustable: 1 to 100V/V, Single Resistor Low Nonlinearity Error: 0.05% max (275L) Low Offset Drift: 5V/C max (275L) Meets MIIL-STD-202E Environmental Testing Low Cost APPLICATIONS Process Signal Isolator Interface Buffer Floating Off-Ground Signal Measurements High Voltage Instrumentation Amplifier Current Shunt Measurements GENERAL DESCRIPTION Model 275 represents a new generation of high performance isolation amplifiers featuring 3-port isolation and improved high accuracy specifications for instrumentation and industrial applications. This new design offers 2500V total ground isolation between inputs and outputs (or power inputs) as well as $200V dc isolation between outputs and power inputs. In- corporating a fully guarded input, common mode rejection at 60Hz and 1k2 source imbalance is guaranteed to be 120dB min with typical performance of 150dB at dc. The low coupling capacitance between inputs and output yields a ground leakage current of less than 8A at a 115V ac 60Hz. In addition to the high +2.5kV CMV rating, the differential input is protected for 125V rms (600V peak) overloads. Three accuracy selections are available offering guaranteed low nonlinearity error at 20V p-p output; 275L: 0.1% max, 275K: 0.15% max and 275J: 0.2% max. Lower nonlinearity error is also guaranteed at 10V p-p output; 275L: 0.05% max, 275K: 0.1% max, 275]: 0.15% max. Using modulation techniques with transformer isolation (sce Figure 1, Block Diagram) for reliable operation, these new models offer +10V input and output signal dynamic range. Soe ee ee eee A DC TO 1.5kHz BIPOLAR INPUT 1 G+ 1TO 1W0V/V AMPLIFIER { 27K W i HiIN G) + | t+-{5) HI OUT MoD i DEMOD FULTER GAIN . 7] \ 5) LO OUT I R ANY I r0000F [10000 0.02uF a) nL 30K82 { oN LOINe 3G . | 200 Tz +200V 15V C 4 + +15VDC POWER SHIELO com HIE] OSCILLATOR (8) GQ GUARD 7 -15V | SOkH2 POWER COM oe DC POWER SUPPLY | Figure 1. Block Diagram Model 275 High CMV, Three Port, High Accuracy, Isolation Amplifier NSO! PROCESS sensor COMPUTER HIGH OUT L Low out SIGNAL COMMON SHIELD +1SV PWR +1SV COM POWER SUPPLY Other unique features of model 275 include single resistor gain adjustment over the range 1 to 100V/V and input offset voltage drift guaranteed for each model; 275L: 5uV/C max, 275K: 15uV/C max, and 275}: 25uV/C max (G = 100V/V). Ideal for portable equipment, model 275 will operate from a single dc supply at any voltage from +12V to +18V, requiring only 15mA current. Single-resistor gain adjustment, 3-port isolation, high CMV and CMR ratings, as well as input overload protection, combine to make these new isolators an excellent choice for all critical in- terface applications; high voltage instrumentation, process sig- nal isolators, current shunt measurements, pH control systems and computer interface systems. HIGH RELIABILITY Model 275 isolators are conservatively designed, compact, low profile (0.88 height), epoxy encapsulated modules capable of reliable operation in harsh environments. These models are designed to meet MIL-STD-202E environmental testing; high humidity, vibration, shock, temperature cycling, etc. (see ENVIRONMENTAL SPECIFICATIONS). Model 275 offers excellent noise immunity to EMI/RFI radiation from motors, relays and power line frequencies, thereby enabling measure- ments to be performed in noisy industrial environments ISOLATION AMPLIFIERS 129SPECIFICATIONS (typical @ +25C and +15V dc unless otherwise noted) MODEL GAIN (NON INVERTING) Range (50kQ2 Load)! Formula Deviation from Formula vs. Temperature (0 to +70C) vs. Temperature (0 to +70C) Nonlinearity, +5V Output Nonlinearity*, 10V Output 110 100V/V 1 -- GOkKQ/R -0, +4% +0.008%/C max +0.015%/C max +0.15% max +0.2% max 2) 275K * # * +0.004%/C max +0.01%/C max +0.1% max +0.15% max 275L * * # +0.004%/C max 0.01%/C max +0.05 % max +0.1% max INPUT VOLTAGE RATINGS Linear Differential Range Max Safe Differential Input Continuous Pulse, 5ms Duration, One Pulse/Sec Max CMV, Inputs to Outputs/Power Common ac, 60Hz, 1 Minute Duration Continuous, ac or de CMR, Inputs to Outputs, 60Hz, Rg < 5kQ Balanced Source Impedance 1kQ Source Impedance Imbalance CMR, Inputs to Guard, 60Hz 1kQ Source Impedance Imbalance Max Leakage Current, Inputs to Common 115V ac, 60Hz +10V min 1Z75V rms t00V pk 3000V rms 2.500V pk max 126dB 120dB min 75dB 8uA rms max OFFSET VOLTAGE, REFERRED TO INPUT Initial, @ +25%C (Adjustable to Zero) vs. Temperature (0 to +70C) Gain = 1V/V Gain = 100V/V At Other Gains (uV/C max) vs. Supply Voltage +(4 + 46/G)mV max +500uV/C max +25uV/C max +(23 + 277/G) (1 + 50/G)uV/V +200UV/C max 15uV/C max +(13 + 187/G) * 100nV/C max +5uV/C max (4 + 96/G) INPUT IMPEDANCE Differential Overload Common Mode 10 OQ 3pe 272. 10''Q100pF INPUT DIFFERENCE CURRENT Initial, @ +25C 7nA max * * vs. Temperature (0 to +70C) +0.1nA/C * * INPUT NOISE Voltage, Gain = 100V/V 0.01Hz to 10Hz Suv p-p * * 10Hz to 1kHz 1.5pV rms * * Current 0.01Hz to 10Hz 1pA p-p * * FREQUENCY RESPONSE Small Signal, -3dB, Gain = 100V/V 1.5kHz * * Full Power, 20V p-p Output 300 Hz * . Slew Rate 0.15 V/ps * * RATED OUTPUT Voltage, 30k2 Load* +10V min * * Output Impedance 1.5kQ. * * Max CMV, Outputs to Power Inputs Peak ac or de Continuous 200V * * POWER SUPPLY SINGLE POLARITY Voltage, Rated Performance +15V dc * * Voltage, Operating Current, Quiescent +12 to 18)V de +15mA TEMPERATURE RANGE Rated Performance Storage 0 to +70C -35C to +85C CASE DIMENSIONS 3.5" x 2.5" x 0.88" *Specifications sarne as model 275J ' Gains up to 1000V/V may be selected by the user with derated performance. 7 Gain temperature drift is specified as % of output voltage. > Gain nonlinearity error is specified as % of peak-to-peak output voltage span. (see Figure 2). * For 2k9. loads, consider model 285 isolation amplifier. 5 Recommended power supply, ADI model 904, +15V @ SOmA output Specifications subject to change without notice. 130 ISOLATION AMPLIFIERS OUTLINE DIMENSIONS Dimensions shown in inches and (mm). MODEL 275 0.89 (22.60) MAX U v v_ {|e 0.04 (10.40) DIA 3.53 (89.66) MAX 0.20 (5.08) MIN 0.25 (6.35) MAX SHIELD GUARD 4 PWR 4.40 NC LO IN (2 PLACES) BOTTOM VIEW 9.1 (2.54) GRID WEIGHT: 250 gms. SHIELDED MOUNTING SOCKET AC1007 Le yp Lo wher See \ 1 80 (96 52) ~~ EY oso Min 27) mma 1.90148 26) oe Oran tia Hore (eLares) we 50 1a Me a 1 12 oN ou 02 o400 I 128 45) H - i 15.08) 110 161 1900. SHEL d t 2.41 ama 100 fF |} SuaRO t 268 56. (254) 9 50 T (67 061 930, fon com Fd 1.000 . a2! 9400 3841 10 15.08) 110 16) t w 1 ae I ry. au Gs t ! at + owoanoe 7] atu | 42 PLACES! 7 13g) | i i be aah NO CONNECTION | ~ 2 700 168 5a) | REQUIAEC On nares le so. is BOTTOM VIEW WEIGHT: 50 gms. GUARDING TECHNIQUES Careful design and packaging of model 275 has yielded extremely high CMR and CMV ratings. To preserve the high CMR, care should be taken to keep the capacitance balanced about the input terminals and guard the gain setting resistor, Rg, for gains less than 5V/V. A recommended shielding technique is illustrated in Figure 10, using model AC1007 mounting socket. This socket is recommended to reduce noise, pick- up, and CMR degradation from stray capacitance. Solder feed-through wire (H) to the socket shield pin and cop- per foil surface. Module will cover shield from further exposure. Best CMR performance will be achieved by using twisted, shielded cable to reduce inductive and capaci- tive pickup. To reduce effective cable capacitance, cable shield should be connected to the common mode signal source. This is accomplished by con- necting the shield as close as possible to signal low, as shown in Figure 10. To avoid ground loops, signal low or cable shield should never be grounded at more than one point.such as electric power and electro-chemical plants. When placed between transducers and delicate monitoring equipment (com- puters, chart recorders, etc.), these isolators will interrupt ground loops, leakage paths and damaging high voltage trans- ients for improved system protection. ENVIRONMENTAL SPECIFICATIONS The reliability of instrumentation and control systems is be- coming more important as the systems being controlled or measured become more complex and more expensive. To pro- vide the reliability needed to protect plant and personnel during environmental stresses (vibration, humidity, temperature, etc.), model 275 has been designed to meet the environmental require- ments of MIL-STD-202E testing, as shown in Table 1. These conditions closely simulate those seen in typical industrial appli- cations. As an additional assurance of high performance relia- bility, every model 275 is factory tested for CMV rating by application of 1800V rms (2500V peak) between input and output terminals for one minute. All Units Meet the Requirements of MIL-STD-202E as Outlined Below TEST METHOD CONDITION Iligh Temperature Storage 108A D (Non-Operating) Moisture Resistance 106D (10 Days) Solderability 208C Thermal Shock 107D A (5 Cycles) Terminal Strength 211A A (Pull Test; 10 Ibs) Temperature Cycling 102A D (-55C/+85 C) Vibration 204C B (15g Peak) Barometric Pressure 105C B (50,000 Feet) TABLE 1. Environmental Specifications PERFORMANCE CHARACTERISTICS Gain Nonlinearity: Nonlinearity error is presented as a % of peak-to-peak output voltage span; c.g. t0.05% @ 10V p-p out- put = 5mV max RTO nonlinearity error. Model 275 1s avail- able in three nonlinearity selections; 0.05% (275L), 0.1% (275K) and 0.15% (275]) max, @ 10V p-p output span. Nonlinearity error is also specified and guaranteed at 20V p-p output span; 0.1%, 0.15% and 0.2% max. The curves of Figure 2 illustrate typical nonlinearity error over the entire output voltage range to 20V p-p (410V). At output levels less than 10V p-p (+5V), nonlinearity error is typically much better than 0.1% for both models 275J and 275K. Appropriate gain should be selected for best performance. 0.20 - 276. (10.2% ~ | [ Ng om. ft o- j _ J GUARANTEL to MAX NONLINEARITY | Bx, WV pp & . ZY ger - 27-0 {/ 5 2750-0 Wokt 3 _ 2K coarse / zg 880" GuaRANTERD 7 ~~ 4 ! MAX NONLINE ANY / BS orb Ste love te . { 1 ZIG CO V%I a { 6 owe + ry 275. OVE z zoe . er z f = 275L (0 6%) g 0.06 T- sfenn Zz 3 00a i 5 4 0.02 = L | - 0 2 4 6 8 WW Ww Ww 6 Ww 2 OUTPUT VOLTAGE Volts pp Figure 2. Gain Nonlinearity Error vs. Output Voltage Common Mode Rejection: CMR is rated at 115V ac, 60Hz and 1kQ source imbalance for all gains from 1 to 100V/V. CMR typically improves by 10dB above the specified minimum at a gain of 100V/V. As a function of frequency, CMR response approaches 150dB at de for all gains. (see Figure 3). TTT T CUARAN TEED CMR 12UdB MIN @ 6OHz WITH 1kS2 SOURCE__ IMBALANCE pe | TEST CIRCUIT 1k32 EACH RESISTOR | 20 CMR VALUE GIVEN FOR WORST CASE RESISTOR COMBINATION | Let dd Lot tT 1 10 100 1k 10k FREQUENCY - Hz COMMON MODE REJECTION -- dB Figure 3. Common Mode Rejection vs. Frequency Input Offset Voltage Drift: Model 275 is available in three drift selections; 5uV/C (275L), 15UV/C (275K), and 25uV/C (275J) max, RTI, G = 100V/V. Total input drift is composed of two sources, (input and output stage drifts) and is gain depen- dent. The curves of Figure 4 illustrate worst case total input drift over the gain range of 1 to 100V/V. Max limits at G = 1V/V and G = 100V/V are also shown. 1600 e- "MAX INPUT DRIFT PSE pe i : { s00b2 @G= WV pate 2755 {300pV/ ce) : = 275K !200pVi C}- : | | MAX INPUT DRIFT OG 100v/V _ __ 100 <= 2751, (100nv/ sot MODEL 275J.|.. . , 2PBI ABN C) T MODEL 275K WORST CASE INPUT VOLTAGE ORIFT - uV Ee eo T= IMAX) PE Bo ware L AS MODEL 2751. ~ [ i Yr (MAX) t j i 1 L | | | | | aL 1 1 10 20 30 40 90 60 70 80 90 100 GAIN V/V Figure 4. Input Offset Voltage Drift (Worst Case) vs. Gain Input Voltage Noise: Voltage noise, referred to input, is depen- dent on gain and bandwidth as illustrated in Figure 5. RMS vol- tage noise is shown in a bandwidth from 0.01Hz to the fre- quency shown on the horizontal axis. The noise in a bandwidth from 0.01Hz to 1kHz is 10uV p-p @ G = 100V/V. This value is derived by multiplying the rms value at f = 1kHz shown in Figure 5 (1.5uV rms) by 6.6. For best noise performance in particular applications, a low pass filter at the output can be used to selectively roll-off noise and undesired signal frequen- cies beyond the bandwidth of interest (sce Figure 10B). Increas- ing gain will also reduce input noise. TT bo INPUT VOLTAGE NOISE ~ 0 V rns* nt = | cet i s : 1 10 100 BANUWIDTH (3481 He Figure 5. Input Voltage Noise vs. Bandwidth ISOLATION AMPLIFIERS 131APPLICATIONS IN INSTRUMENTATION AND PROCESS CONTROL Interface Buffer Amplifier: Isolators are used in complex indus- trial systems to control, measure and interface other segments of the manufacturing/process operation and provide protection against damage caused by high voltage transients as well as con- tinuous fault voltages. Model 275s unique three port isolation capability not only provides protection against high input com- mon mode voltages (F2000V dc continuous), but also offers protection against high output common mode voltages (200V dc continuous, form HI OUT and LO OUT, to POWER COM). Inthe computer interface applicaticn of Figure 6, model 275 will protect both the input sensor and power supply from computer faults causing ac line voltage to simultaneously appear at both output terminals of model 275. PROCESS 275" COMPUTER HIGH OUT _ SENSOR , LOW OUT 5 4 SIGNAL AC POWER COMMON ineuT ~ SHIELD PWR COM VISVAC +15V PWR FOR OPTIONAL GAIN, OFFSET VOLTAGE ZEROING ANO BANDWIDTH ROLLOFF, SEE FIGURE 10. +15V COM JE POWER POWER SUPPLY INPUT ADI 904 Figure 6. Computer Interfece Buffer Current Shunt Measurements: Model 275's high CMV (+2.5kV) and differential input protection (t600V peak pulse) makes it particularly suitable for measuring SCR gate-to-cathode voltages typical in motor-control circuits (see Figure 7). The isolators wide bandwidth (de to 1.5kHz) and single resistor gain adjust- ment (1V/V to 100V/V) provide the performance required to accurately measure low level current signals from typical 5|0mV and 100mV shunts. 275 HIGH OUT TO INDICATOR AND CHART RECORDER *FOR 10V FULL SCALE QUTPUT, - 0012 taquT 9 (GAIN = 100V/V) SCR CONTROL IF SPEED OR TOR UE '3-PHASE' MOTOR, #4 ee ee 2 HE SHUNT iheur aA var __-|>+-_~ y Figure 7. Motor Current Monitor Application Qo-- Process Signal Isolator: Model 275 can be easily applied in pro- cess control loops to interface standard process signals (e.g. 1 to 5mA, 4 to 20mA, 10 to 50mA, etc.) and convert them to standard, zero based voltage signals (e.g. 0 to +10V). A typical hook-up of model 275 is illustrated in Figure 8, showing input current resistor (Rs), full scale span adjustment (Rg) and a zero adjust pot. The table lists typical values for standard process signals, assuming a 0 to +10V output span is desired. Model 275s righ 60Hz CMR rating (120dB min) and high CMV isola- tion (2kV de) permits interfacing with long control loops typical in industrial plant applications. INPUT RESISTOR CONVERTS LOOP CURRENT 100.1V TO 0.5V INPUT SPAN ADJUST MODEL 318A GOR EGuiv ZERO ADJUST "ADJUST Ey TOO VOLTS. Loop Current [Input Resistor |Span Resistor [Output Span Rs R, E fin 9 WITH iy AT MINIMUM LEVEL 1 - SmA 10082 1.24kQr Oto +10V 4 ~ 20mA 252 1.24k2 0 to +10V 10 - 50mA 1082 1.24k82 Oto +10V Figure 8. Process Signal Isolator, Showing Resistor Values for Typical Process Signal Levels Bridge Transducer Amplifier: Model 275 offers total ground isolation with simplified two wire hook-up for low-level, floating signal measurements such as remote balanced bridge circuits (see Figure 9). Only differential current flows between the High Input and Low Input terminals of model 275, eliminating a third-wire for bias current return (required with ail other types of amplifiers). The 100MQ differential input impedance of model 275 will not load the bridge circuit. High CMV rating permits the bridge to be floated up to +2kV dc with respect to power ground. CABLE Palit 275 HIGH Low 7 SHIELD LSUARO Figure 9. Bridge Transducer Amplifier BRIDGE * EXCITATION BRIDGE AC 1007 MOUNTING 17 SOCKET SHIELD TRANSDUCER ABL TRANSDUCER c e SIGNAL M IDEL 275 FLOATING GUARD-SHIELD SHIELD TRANSDUCER GROUND (NOT REQUIRED) LOAD GROUND i \ = (CONNECT POWER GROUND Veen, 2000VDC MAX poweg TO LOAD GROUND IF NOTE J Gain Resistor, Ry. 1%, 25ppm/ C metal him type is recommended - GROUND) FLOATING OUTPUT For Gaim - 2, leave gain terminat 4 open Is NOT REQUIRED! Gain 19 902 ign Rg) Rg Figure 10A. Transducer, Power, Gain Resistor, and Shielding Interconnection ISOLATOR INTERCONNECTION CURRENT BOOSTER BANDWIDTH ROLLOFF Pro ALL. 1 (-3dB) = _.- BOKS? Not Required 2a (1.5kQ} 2k BA 50082 1194 10082 8-100 ac 10ks2 Re pw 07180 4 OFFSET VOLTAGE TRIM ADJUST + SE > 2OKSE M 20082 2 z 5V 4 TOKE PWR COM PWR COM Figure 10B. Optional Connections: Offset Voltage Trim Aajust, Bandwidth (-3dB) Roiloff and Current Booster Amplifier 732 ISOLATION AMPLIFIERS