® XTR115 XTR116 XTR 116 XTR 115 For most current data sheet and other product information, visit www.burr-brown.com 4-20mA CURRENT LOOP TRANSMITTERS FEATURES APPLICATIONS ● LOW QUIESCENT CURRENT: 200µA ● 2-WIRE, 4-20mA CURRENT LOOP TRANSMITTER ● 5V REGULATOR FOR EXTERNAL CIRCUITS ● VREF FOR SENSOR EXCITATION: ● SMART TRANSMITTER ● INDUSTRIAL PROCESS CONTROL XTR115: 2.5V XTR116: 4.096V ● LOW SPAN ERROR: 0.05% ● TEST SYSTEMS ● COMPATIBLE WITH HART MODEM ● LOW NONLINEARITY ERROR: 0.003% ● WIDE LOOP SUPPLY RANGE: 7.5V to 36V ● CURRENT AMPLIFIER ● VOLTAGE-TO-CURRENT AMPLIFIER ● SO-8 PACKAGE DESCRIPTION used for offsetting or to excite transducers. A current return pin (IRET) senses any current used in external circuitry to assure an accurate control of the output current. The XTR115 is a fundamental building block of smart sensors using 4-to-20mA current transmission. The XTR115 and XTR116 are precision current output converters designed to transmit analog 4-to-20mA signals over an industry standard current loop. They provide accurate current scaling and output current limit functions. The XTR115 and XTR116 are specified for operation over the extended industrial temperature range, –40°C to +85°C. The on-chip voltage regulator (5V) can be used to power external circuitry. A precision on-chip VREF (2.5V for XTR115 and 4.096V for XTR116) can be XTR115 XTR116 VREG +5V +5V Regulator 8 VREF XTR115: 2.5V XTR116: 4.096V 1 V+ 7 Voltage Reference VLOOP RIN B 6 IIN 2 + RL A1 E 5 VIN – RLIM 3 IRET R1 2.475kΩ R2 25Ω IO = 100 VIN RIN 4 I = 100 • IIN International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 ® © 2000 Burr-Brown Corporation PDS-1582A 1 in U.S.A. January, 2000 XTR115,Printed XTR116 SPECIFICATIONS At TA = +25°C, V+ = 24V, RIN = 20kΩ, and TIP29C external transistor, unless otherwise noted. XTR115U XTR116U PARAMETER CONDITIONS OUTPUT Output Current Equation Output Current, Linear Range Over-Scale Limit Under-Scale Limit SPAN Span (Current Gain) Error (1) vs Temperature Nonlinearity INPUT Offset Voltage (Op Amp) vs Temperature vs Supply Voltage, V+ Bias Current vs Temperature Noise: 0.1Hz to 10Hz IREG = 0, IREF = 0 32 0.2 IIN = 250µA to 25mA TA = –40°C to +85°C IIN = 250µA to 25mA 100 ±0.05 ±3 ±0.003 ILIM IMIN S VOS MIN 25 ✻ TYP MAX UNITS ✻ 0.25 ✻ ✻ ✻ mA mA mA ±0.2 ±20 ±0.01 ✻ ✻ ✻ ✻ ±0.4 ✻ ±0.02 A/A % ppm/°C % IIN = 40µA TA = –40°C to +85°C V+ = 7.5V to 36V ±100 ±0.7 ±0.1 –35 150 0.6 CLOOP = 0, R L = 0 380 3.2 ✻ ✻ kHz mA/µs 2.5 4.096 ±0.05 ±20 ±1 ±100 10 16 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ V V % ppm/°C ppm/V ppm/mA µVp-p mA IB en IREF = 0 TA = –40°C to +85°C V+ = 7.5V to 36V IREF = 0mA to 2.5mA VREG(2) Voltage Voltage Accuracy vs Temperature vs Supply Voltage, V+ vs Output Current Short-Circuit Current MAX ✻ 0.25 VREF(2) XTR115 XTR116 Voltage Accuracy vs Temperature vs Supply Voltage, V+ vs Load Noise: 0.1Hz to 10Hz Short-Circuit Current TEMPERATURE RANGE Specification Operating Storage Thermal Resistance TYP IO = IIN • 100 IO DYNAMIC RESPONSE Small Signal Bandwidth Slew Rate POWER SUPPLY Specified Voltage Range Quiescent Current Over Temperature, –40°C to +85°C MIN XTR115UA XTR116UA ±250 ±3 ±2 ✻ ✻ ✻ ✻ ✻ ✻ ±0.25 ±35 ±10 ✻ ✻ ✻ ✻ 5 ±0.05 ±0.1 ±0.1 1 See Typical Curves 12 IREG = 0 TA = –40°C to +85°C V+ = 7.5V to 36V ±500 ±6 ✻ ±0.5 ±75 ✻ ✻ ✻ µV µV/°C µV/V nA pA/°C µVp-p V V mV/°C mV/V mA V+ ✻ +24 +7.5 200 240 –40 –55 –55 θJA 150 ✻ Specifications the same as XTR115U and XTR116U. NOTES: (1) Does not include initial error or TCR of RIN. (2) Voltage measured with respect to IRET pin. ® XTR115, XTR116 2 +36 250 300 ✻ +85 +125 +125 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ V V µA µA °C °C °C °C/W ABSOLUTE MAXIMUM RATINGS(1) PIN CONFIGURATION Top View Power Supply, V+ (referenced to IO pin) .......................................... 40V Input Voltage (referenced to IRET pin) ........................................ 0V to V+ Output Current Limit ............................................................... Continuous VREG, Short-Circuit .................................................................. Continuous VREF, Short-Circuit .................................................................. Continuous Operating Temperature ................................................ –55°C to +125°C Storage Temperature Range ....................................... –55°C to +125°C Lead Temperature (soldering, 10s) .............................................. +300°C Junction Temperature ................................................................... +165°C SO-8 VREF 1 8 VREG IIN 2 7 V+ IRET 3 6 B (Base) IO 4 5 E (Emitter) NOTE: (1) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device reliability. ELECTROSTATIC DISCHARGE SENSITIVITY This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. PACKAGE/ORDERING INFORMATION PRODUCT PACKAGE PACKAGE DRAWING NUMBER XTR115UA SO-8 182 –40°C to +85°C XTR115UA XTR115UA Rails " " " " XTR115UA/2K5 Tape and Reel SO-8 182 –40°C to +85°C XTR115U " " " " XTR115U XTR115U/2K5 Rails Tape and Reel SO-8 182 –40°C to +85°C XTR116UA " " " " XTR116UA XTR116UA/2K5 Rails Tape and Reel SO-8 182 –40°C to +85°C XTR116U XTR116U Rails " " " " XTR116U/2K5 Tape and Reel " XTR115U " XTR116UA " XTR116U " SPECIFIED TEMPERATURE RANGE PACKAGE MARKING ORDERING NUMBER(1) TRANSPORT MEDIA NOTES: (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces of “XTR115UA/2K5” will get a single 2500-piece Tape and Reel. The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems. ® 3 XTR115, XTR116 TYPICAL PERFORMANCE CURVES At TA = +25°C, V+ = 24V, RIN = 20kΩ, and TIP29C external transistor, unless otherwise noted. CURRENT GAIN vs FREQUENCY QUIESCENT CURRENT vs TEMPERATURE 260 Quiescent Current (µA) Gain (dB) 40 COUT = 0 RL = 0Ω 30 COUT = 10nF RL = 250Ω 20 10 240 (V+) = 36V 220 (V+) = 24V 200 (V+) = 7.5V 180 160 10k 100k 1M –75 –50 –25 0 Frequency (Hz) 25 50 75 100 125 Temperature (°C) REFERENCE VOLTAGE vs TEMPERATURE OVER-SCALE CURRENT vs TEMPERATURE 0.1 34 Over-Scale Current (mA) ∆ Reference Voltage (%) With External Transistor 0 –0.1 –0.2 33 32 V+ = 36V 31 V+ = 7.5V 30 V+ = 24V 29 –0.3 28 –75 –50 –25 0 25 50 75 100 125 –75 Temperature (°C) +125°C VREG Voltage (V) –55°C +25°C –55°C 5.0 +25°C Sinking Current Sourcing Current +125°C 4.5 –1 0 1 2 3 4 IREG Current (mA) ® XTR115, XTR116 –25 0 25 50 Temperature (°C) VREG VOLTAGE vs VREG CURRENT 5.5 –50 4 75 100 125 APPLICATIONS INFORMATION and upward. Full-scale inputs greater than 0.5V are recommend to minimize the effect of offset voltage and drift of A1. The XTR115 and XTR116 are identical devices except for the reference voltage output, pin 1. This voltage is available for external circuitry and is not used internally. Further discussions that apply to both devices will refer to the “XTR115/6.” EXTERNAL TRANSISTOR The external transistor, Q1, conducts the majority of the fullscale output current. Power dissipation in this transistor can approach 0.8W with high loop voltage (40V) and 20mA output current. The XTR115/6 is designed to use an external transistor to avoid on-chip thermal-induced errors. Heat produced by Q1 will still cause ambient temperature changes that can affect the XTR115/6. To minimize these effects, locate Q1 away from sensitive analog circuitry, including XTR115/6. Mount Q1 so that heat is conducted to the outside of the transducer housing. Figure 1 shows basic circuit connections with representative simplified input circuitry. The XTR115/6 is a two-wire current transmitter. Its input signal (pin 2) controls the output current. A portion of this current flows into the V+ power supply, pin 7. The remaining current flows in Q1. External input circuitry connected to the XTR115/6 can be powered from VREG or VREF. Current drawn from these terminals must be returned to IRET, pin 3. This IRET pin is a “local ground” for input circuitry driving the XTR115/6. The XTR115/6 is designed to use virtually any NPN transistor with sufficient voltage, current and power rating. Case style and thermal mounting considerations often influence the choice for any given application. Several possible choices are listed in Figure 1. A MOSFET transistor will not improve the accuracy of the XTR115/6 and is not recommended. The XTR115/6 is a current-input device with a gain of 100. A current flowing into pin 2 produces IO = 100 • IIN. The input voltage at the IIN pin is zero (referred to the IRET pin). A voltage input is created with an external input resistor, as shown. Common full-scale input voltages range from 1V XTR115 XTR116 IREG 5V XTR115: 2.5V XTR116: 4.096V IO VREG +5V Regulator 8 IREF VREF 1 V+ 7 Voltage Reference VLOOP Input Circuitry VIN RIN 20kΩ IIN B IIN 2 6 Q1 10nF RL A1 E 5 RLIM 3 All return current from IREG and IREF IRET R1 2.475kΩ R2 25Ω IO 4 I = 100 • IIN For IO = 4mA to 20mA IIN = 40µA to 200µA With RIN = 20kΩ VIN = 0.8V to 4V Possible choices for Q1 (see text). TYPE PACKAGE 2N4922 TIP29C TIP31B TO-225 TO-220 TO-220 FIGURE 1. Basic Circuit Connections. ® 5 XTR115, XTR116 MINIMUM-SCALE CURRENT MAXIMUM OUTPUT CURRENT The quiescent current of the XTR115/6 (typically 200µA) is the lower limit of its output current. Zero input current (IIN = 0) will produce an IO equal to the quiescent current. Output current will not begin to increase until IIN > IQ /100. Current drawn from VREF or VREG will add to this minimum output current. This means that more than 3.7mA is available to power external circuitry while still allowing the output current to go below 4mA. The XTR115/6 provides accurate, linear output up to 25mA. Internal circuitry limits the output current to approximately 32mA to protect the transmitter and loop power/measurement circuitry. It is possible to extend the output current range of the XTR115/6 by connecting an external resistor from pin 3 to pin 5, to change the current limit value. Since all output current must flow through internal resistors, it is possible to damage with excessive current. Output currents greater than 45mA may cause permanent damage. OFFSETTING THE INPUT A low scale of 4mA is produced by creating a 40µA input current. This can be created with the proper value resistor from VREF (Figure 2), or by generating offset in the input drive circuitry. VREG XTR115 XTR116 VREF VO D/A XTR115 RIN VREG VREG VREF Voltage Reference 40µA XTR115 XTR116 VREF R0 62.5kΩ Digital Control IIN IO D/A ≈ 2.5V Optical Isolation IIN IRET A1 0 to 160µA IRET Digital Control R1 2.475kΩ ≈ 5V µC PWM Out VREG Filter RIN Optical Isolation IRET FIGURE 2. Creating Low-Scale Offset. FIGURE 3. Digital Control Methods. ® XTR115, XTR116 6 XTR115 XTR116 REVERSE-VOLTAGE PROTECTION Most surge protection zener diodes have a diode characteristic in the forward direction that will conduct excessive current, possibly damaging receiving-side circuitry if the loop connections are reversed. If a surge protection diode is used, a series diode or diode bridge should be used for protection against reversed connections. The XTR115/6 low compliance voltage rating (7.5V) permits the use of various voltage protection methods without compromising operating range. Figure 4 shows a diode bridge circuit which allows normal operation even when the voltage connection lines are reversed. The bridge causes a two diode drop (approximately 1.4V) loss in loop supply voltage. This results in a compliance voltage of approximately 9V—satisfactory for most applications. A diode can be inserted in series with the loop supply voltage and the V+ pin to protect against reverse output connection lines with only a 0.7V loss in loop supply voltage. RADIO FREQUENCY INTERFERENCE The long wire lengths of current loops invite radio frequency interference. RF can be rectified by the input circuitry of the XTR115/6 or preceding circuitry. This generally appears as an unstable output current that varies with the position of loop supply or input wiring. OVER-VOLTAGE SURGE PROTECTION Interference may also enter at the input terminals. For integrated transmitter assemblies with short connection to the sensor, the interference more likely comes from the current loop connections. Remote connections to current transmitters can sometimes be subjected to voltage surges. It is prudent to limit the maximum surge voltage applied to the XTR115/6 to as low as practical. Various zener diode and surge clamping diodes are specially designed for this purpose. Select a clamp diode with as low a voltage rating as possible for best protection. For example, a 36V protection diode will assure proper transmitter operation at normal loop voltages, yet will provide an appropriate level of protection against voltage surges. Characterization tests on several production lots showed no damage with loop supply voltages up to 65V. 8 V+ VREG 1 RIN 2 VREF IIN VIN XTR115 XTR116 B E 3 Maximum VPS must be less than minimum voltage rating of zener diode. 7 IRET IO 6 Q1 0.01µF D1(1) 1N4148 Diodes RL 5 VPS The diode bridge causes a 1.4V loss in loop supply voltage. 4 NOTE: (1) Zener Diode 36V: 1N4753A or Motorola P6KE39A. Use lower voltage zener diodes with loop power supply voltages less than 30V for increased protection. See “Over-Voltage Surge Protection.” FIGURE 4. Reverse Voltage Operation and Over-Voltage Surge Protection. ® 7 XTR115, XTR116