[A bevices Precision, Wide Bandwidth, Synchronized Isolation Amplifier MODEL 289 FEATURES Low Nonlinearity: +0.012% max (289L) Frequency Response: (-3dB) de to 20kHz (Full Power) dc to 5kHz Gain Adjustable 1 to 100V/V, Single Resistor 3-Port Isolation: +2500V CMV Isolation Input/Output Low Gain Drift: 0.005%/C max Floating Power Output: +15V @ t5mA 120dB CMR at 60Hz: Fully Shielded Input Stage Meets UL Std. 544 Leakage: 2uA rms max, @ 115V ac, GOHz APPLICATIONS Multi-Channel Data Acquisition Systems Current Shunt Measurements Process Signal Isolator : High Voltage Instrumentation Amplifier SCR Motor Control GENERAL DESCRIPTION Model 289 is a wideband, accurate, low cost isolation ampli- fier designed for instrumentation and industrial applications. Three accuracy selections are available offering guaranteed gain nonlinearity error at 10V p-p output: 0,012% max (289L), 0.025% max (289K), 0.05% max (289J). All ver- sions of the 289 provide a small signal frequency response from de to 20kHz (~3dB) and a large signal response from dc to 5kHz (full power) at a gain of 1V/V. This new design offers true 3-port isolation, 2500V dc between inputs and outputs (or power inputs), as well as 240V rms between power supply inputs and signal outputs. Using carrier modulation tech- niques with transformer isolation, mod21 289 interrupts ground loops and leakage paths and minimizes the effect of high voltage transients. It provides 120dB Common Mode Rejection between input and output common. The high CMV and CMR ratings of the model 289 faci.itate accurate measure- ments in the presence of noisy electrical equipment such as motors and relays. WHERE TO USE THE MODEL 289 The model 289 is designed to interface single and multichannel data acquisition systems with dc sensors such as thermo- couples, strain gauges and other low level signals in harsh in- dustrial environments. Providing high accuracy with complete galvanic isolation, and protection from line transients of fault voltages, model 289s performance is suitable for applications such as process controllers, current loop receivers, weighing systems, high CMV instrumentation and computer inter- face systems. Use the model 289 when data must be acquired from floating transducers in computerized process control systems. The photograph above shows a typical multichannel application allowing potential differences or interrupting ground loops, among transducers, or between transducers and local ground. DATA ACOUISITION SYSTEM DESIGN FEATURES AND USER BENEFITS Isolated Power: The floating power supply section provides isolated +15V outputs @ +5mA. Isolated power is regulated to within +5%. This feature permits model 289 to excite floating signal conditioners, front-end buffer amplifiers and remote transducers such as thermistors or bridges, eliminating the need for a separate isolated dc/de converter. Adjustable Gain: A single external resistor adjusts the model 289s gain from 1V/V to 100V/V for applications in high and low level transducer interfacing. Synchronized: The model 289 provides a synchronization terminal for use in multichannel applications. Connecting the synchronization terminals of model 289s synchronizes their internal oscillators, thereby eliminating the problem of oscil- lator beat frequency interference that sometimes occurs when isolation amplifiers are closely mounted. Internal Voltage Regulator: Improves power supply rejection and helps prevent carrier oscillator spikes from being broad- cast via the isolator power terminal to the rest of the system. Buffered Output: Prevents gain errors when an isolation ampli- fier is followed by a resistive load of low impedance. Model 289 can drive a 2kQ load. Three-Port Isolation: Provides true galvanic isolation between input, output and power supply ports. Eliminates need for power supply and output ports being returned through a com- mon terminal. Reliability: Model 289 is conservatively designed to be capable of reliable operation in harsh environments. Model 289 has a calculated MTBF of 271,835 hours. In addition, the model 289 meets UL Std. 544 leakage, 2UA rms @ 115V ac, 60Hz. ISOLATION AMPLIFIERS VOL. II, 5-17SPECIFICATIONS (typical @ +25C and Vs = +14,4V to +25V de unless otherwise noted) Model 289) 289K 289L GAIN (NONINVERTING) Range 1 to 100V/V Formula G=1+ wn ) Deviation from Formula 1.5% max vs, Temperature (0 to +70C)' 1Sppm/C typ (50ppm/C max) Nonlinearity, (#5V Swing)? 0.05% max 0.025% max +0,012% max UNPUT VOLTAGE RATINGS Linear Differential Range (G = 1V/V) +10V min Max Safe Differential Input Continuous 120V rms 1 Minute 240V rms Max CMV (Inputs to Outputs) Continuous ac or de +2500V peak max ac, 60Hz, 1 Minute Duration 2500V rms CMR, Inputs to Outputs 60Hz Rg 1kQ, Balanced Source Impedance 120dB Rg 1kQ, HI IN Lead Only 104dB min Max Leakage Current, Input to Output @ 115V rms, 60Hz ac 2uA rms max INPUT IMPEDANCE Differential 33pFil 10 2 Overload 100k Common Mode 20pF IIs X 10 2 INPUT DIFFERENCE CURRENT Initial @ +25C 10nA (75nA max) vs. Temperature (0 to 70C) O.1SnAPC INPUT NOISE (GAIN = 100V/V) Voltage 0.05Hz to 100Hz 8yuV p-p 10Hz to 1kHz 3yV rms Current 0.05Hz to 100Hz 3pA rms FREQUENCY RESPONSE Small Signal -3dB . G=1V/V 20kHz G=100V/V SkHz Full Power, 10V p-p Output Geiv/V 5kHz G=100V/V 3.SkHz Full Power, 20V p-p Output G=1V/V 2.3kKHz G=100V/V 2.3kHz Slew Rate 0.14V/us Settling Time* +0.05%, +10V Step 400us OFFSET VOLTAGE, REFERRED TO [INPUT 10 Initial, @ +25C 45 4 mV max vs. Ternperature (0 to +70C) 4202 = max #15 2A max +10 #2 uP max vs. Supply Voltage (+15V to +20V change) 10 +2 += V/V t24 G uv/ RATED OUTPUT Voltage, 2kQ Load Output Impedance Output Ripple, 0.1MHz Bandwidth +10V min <1Q(de to 100Hz) No Signal IN SmV p-p +10Vjy 50mV p-p ISOLATED POWER SUPPLY Voltage 15V de Accuracy 10% Current +5mA, min Regulation No Load to Full Load 5% Ripple, 0.1MHz Bandwidth, No Load 25mV p-p Full Load 75mV p-p POWER SUPPLY, SINGLE POLARITY Voltage, Rated Performance +14.4V to +25V Voltage, Operating +8.5V to +25V Current, Quiescent ( Vg = +15V) +25mA. TEMPERATURE RANGE Rated Performance 0 to +70C Operating -15C to 475C Storage -55C to +85C CASE DIMENSIONS 1.5" X 2.0"X 0.75" NOTES "Gain temperacure drift is specified as a percentage of output signal level. ? Gain nonlinearity is specified as a percentage of 10V pk-pk output span. * When isolated power output is used, nonlinesrity increases t y 0.002%/mA of current drawn. *G = 1V/V; with 2-pole, 5kHz output filter. * Recommended power supply, ADI model 904, #15V @ 50n-A output. Specifications subject to change without notice. VOL. Il, 5-18 ISOLATION AMPLIFIERS OUTLINE DIMENSIONS Dimensions shown in inches and (mm). [+ 2.02 {51.18} MAX >) 0.75 MODEL 289 {18.95} MAX = 0.04 (1.02) DIA i 0,20 TO 0.25 (5 TO 6.4) POWER COM SYNC 151 {38.45 LoouT 9 MAX HI OUT 10 BOTTOM VIEW WEIGHT: 40 GRAMS | i 0.1 (2.54) GRID SHIELDED MATING SOCKET AC1214 = 2.7 (68.58) REF a | MAX LL COPPER CLAD SHIELD Lo Om a Z oo C2 dT { 0.50 ~~ " 12.7) MAX 0.093 FEEDTHROUGH WIRE Y (2.29) ~~ REF +Vg 6 POWER COM 7 SYNC 8 1.51 LOOUT 9 (38.1) EF HI OUT 10 BOTTOM VIEW 0.1 (2.84) GRID WEIGHT: 15 GRAMS COPPER CLAD SHIELD INTERCONNECTIONS AND SHIELDING TECHNIQUE To preserve the high CMR performance of model 289, care must be taken to keep the capacitance balanced about the input terminals. A shield should be provided on the printed cir- cuit board under model 289 as illustrated in the outline drawing above (screened area). The LO IN/ISO PWR COM (pin 1) must be connected to this shield. This shield is provided with the mounting socket, model AC1214 (solder feed- through wire to the socket pin 1 and copper foil surface). A recommended shielding tech- nique using model AC1214 is illustrated in Figure 1. Best CMR performance will be achieved by using twisted, shielded cable for the input signal to reduce inductive and capacitive pickup. To further reduce effective cable capacitance, the cable shield should be connected to the com- mon mode signal source as close to signal low as possible (see Figure 1).Understanding the Isolation Amplifier Performance TRANSDUCER CABLE AC1214 BIODEL 288 FLOATING SHIELD TRANSDUCER "Roun (NOT REQUIRED) BOOV de MAX NOTE: GAIN RESISTOR Rg, 1% 50pprn/C METAL FILM TYPE IS RECOMMENDED, FOR GAIN = 1V/V, LEAVE PIN 4 OPEN FOR GAIN > 1V/V, CONNECT GAIN RESISTOR (Rg) BETWEEN PIN 4 AND PIN 1 = kN GAIN = 1+ Fig tk) Terminal Ratings: CMV performance is given in both peak pulse and continuous ac, or de peak ratings. Continuous peak ratings apply from dc up to the normal full power response 2500V rms 1 MINUTE, 2500V pk or de CONT 120V rms CONT 240V ms 1 MIN louTPU Vv INPUT mACONT 2500V rms 1 MINUTE 2500V pk or dc CONT Figure 4. Model 289 Terminal Ratings Figure 3. Model 289 Terminal Capacitance frequencies. Figure 4 illustrates model 289 ratings between terminals. Figure 1. Basic Isolator Interconnection GAIN AND OFFSET TRIM PROCEDURE The following procedure illustrates a calibration technique THEORY OF OPERATION The remarkable performance of the madel 289 is derived from the carrier isolation technique used to transfer both signal and power between the amplifiers input stage and the rest of the circuitry. A block diagram is shown in Figure 2, b 9 _| OuTPUT pb p (SOLATED ide. POWER SUPPLY Iq a2 _ sync WN/OUT WKH -)_ 4 POWER REGULATOR be-(6) DC POWER P | Osct LATOR ___. IN, Vs. b ch pwa com INPUT SHIELD 3 ___ OUT reese Te POWER Figure 2. Model 289 Block Diagram The input signal is filtered and appears at the input of the non- inverting amplifier, Al. This signal is amplified by Al, with its gain determined by the value of resistance connected exter- nally between the gain terminal and the input common termi- nal. The output of Al is modulated, carried across the isola- tion barrier by signal transformer T1, and demodulated. The demodulated voltage is filtered, amplified and buffered by amplifier A2, and applied to the output terminal. The voltage applied to the Vg terminal is set by the regulator to +12V which powers the 100kHz symmetrical square wave power oscillator. The oscillator drives the primary winding of trans- former T2, The secondary windings of T2 energize both input and output power supplies, and drives both the modulator and demodulator. INTERELECTRODE CAPACITANCE AND TERMINAL RATINGS Capacitance: Interelectrode terminal capacitance, arising from stray coupling capacitance effects between the input terminals and the signal output terminals, are each shunted by leakage resistance values exceeding 50GQ: Figure 3 illustrates model _289s capacitance, between terminals. > +10V which can be used to minimize output error. In this example, the output span is +5V to -5V and Gain = 10V/V. 1 2, Apply En = 0 volts and adjust Ro for Eg = 0 volts. Apply Eyn = +0.500V dc and adjust Rg for Eg = +5,000V dc. Apply Eyn = -0.500V dc and measure the output error (see curve a). Adjust Rg until the output error is one-half that measured in step 3 (see curve b). Apply +0.500V de and adjust Rg until the output error is one-half that measured in step 4 (see curve c). OUTPUT ERROR mV 5 4 -3 -2 ~1 oO +1 +2 +3 +4 +5 OUTPUT VOLTAGE Volts Figure 5a. Recommended Offset and Gain Adjustment for Gains > 1 aL S 22 289 10k. +15V 2 ZERO 3 | aosusr > 2002 ~15V 4 10k2 Figure 5b. Recommended Offset Adjustment for G= 1V/V ISOLATION AMPLIFIERS VOL. Il, 5-19PERFORMANCE CHARACTERISTICS 180 160 140 120 PHASE SHIFT - DEGREES % NONLINEARITY 1 10 100 GAIN - V/V FREQUENCY ~ Hz Figure 10. Typical Gain Nonlinearity vs. Gain Figure 6. Typical 289 Phase vs. Frequency a YP COMMON MODE REJECTION 48 COMMON MODE REJECTION 48 SOURCE IMBALANCE ~ {* FREQUENCY -- Hz Figure 7. Typical 289 Common Mode Rejection vs. Source Impedance Figure 11. Typical Common Mode Rejection vs. Frequency : at a Gain of 1V/V, CMR is typically 6B Lower than at a Gain of 100V/V MULTICHANNEL APPLICATIONS on Eom Isolation amplifiers containing interna] oscillators may exhibit nose eran a slowly varying offset voltage at the output when used in multichannel applications, This offset voltage is the result of adjacent internal oscillators beating together, For example, if two adjacent isolation amplifiers have oscillator frequencies of 100,0kHz and 100,1kHz respectively, a portion of the dif- ference frequency may appear as a slowly varying output offset voltage error. Model 289 eliminates this problem by offering a synchronization terminal (pin 8). When this terminal FREQUENCY Hz is interconnected with other model 289 synchronization ter- minals, the units are synchronized. Alternately, one or more units may be synchronized to an external 100kHz +2% square- wave generator by the connection of synchronization termi- al(s) to that generator. The generator output should be 2.5V5.0V p-p with 1kQ source impedance to each unit. Use an external oscillator when you need to sync to an ex- ternal 100kHz source, such as a sub-multiple of a micropro- cessor clock. A differential line driver, such as SN75158, can be used to drive large clusters of model 289. When using the synchronization pin, keep leads as short as possible and do not use shielded wire. These precautions are necessary to avoid capacitance from the synchronization terminal to other points. It should be noted that units synchronized must share the same power common to ensure a return path, INPUT VOLTAGE NOISE pV rms Figure 8. Typical Input Voltage Noise vs. Bandwidth a1 16 OUTPUT SWING P-P VCLTS Figure 9. Typical Gain Nonlinearity vs. Output Swing VOL. Il, 5-20 ISOLATION AMPLIFIERS