LM134H

LM134 LINER | Alldatasheet

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 12

Technical content

n Current Mode Temperature Sensing n Constant Current Source for Shunt References n Cold Junction Compensation n Constant-Gain Bias for Bipolar Differential Stage n Micropower Bias Networks n Buffer for Photoconductive Cell n Current Limiter n 1mA to 10mA Operation n 0.02%/V Regulation n 0.8V to 40V Operating Voltage n Can be Used as Linear Temperature Sensor n Draws No Reverse Current n Supplied in Standard Transistor Packages Constant Current Source and Temperature Sensor The LM134 is a three-terminal current source designed to operate at current levels from 1mA to 10mA, as set by an external resistor. The device operates as a true two- terminal current source, requiring no extra power connec- tions or input signals. Regulation is typically 0.02%/V and terminal-to-terminal voltage can range from 800mV to 40V. Because the operating current is directly proportional to absolute temperature in degrees Kelvin, the device will also find wide applications as a temperature sensor. The temperature dependence of the operating current is 0.336%/°C at room temperature. For example, a device operating at 298mA will have a temperature coefficient of 1mA/°C. The temperature dependence is extremely accu- rate and repeatable. Devices specified as temperature sensors in the 100 mA to 1mA range are the LM134-3, LM234-3 and the LM134-6, LM234-6, with the dash numbers indicating –3°C and –6°C accuracies, respec- tively. If a zero temperature coefficient current source is re- quired, this is easily achieved by adding a diode and a resistor. , LTC and LT are registered trademarks of Linear Technology Corporation. Remote Temperature Sensor with Voltage Output Operating Current vs Temperature R RSET 226Ω VIN ‡ 5V 10k 10mV/°KLM234-3 TA01a OPERATING CURRENT (µA) TEMPERATURE (°K) 500 400 300 200 100 400 TA01b 100 200 300 500 225 125 –75 –175 –275 RSET = 226Ω TEMPERATURE (°C)

V R NC S8 PACKAGE 8-LEAD PLASTIC SO V+ to V– Forward Voltage LM134-3/LM134-6/LM234-3/ ORDER PART NUMBER TJMAX = 150°C, qJA = 440°C/W, qJA = 80°C/W ABSOLUTE AXI U RATI GSW WW U PACKAGE/ORDER I FOR ATIOUU W (Note 1) Consult LTC Marketing for availability of LM234Z-3 and LM234Z-6 Operating Temperature Range ORDER PART NUMBER ORDER PART NUMBER S8 PART MARKING 334 LM334S8 LM134H LM334H LM134H-3 LM234H-3 LM134H-6 LM234H-6 CURRENT SOURCE TEMP SENSOR TJMAX = 100°C, qJA = 160°C/W TJMAX = 100°C, qJA = 180°C/W LM334Z CURRENT SOURCE TEMP SENSOR BOTTOM VIEW Z PACKAGE 3-LEAD PLASTIC TO-92 V–V+ R BOTTOM VIEW H PACKAGE 3-LEAD TO-46 METAL CAN R LM234Z-3 LM234Z-6 OBSOLETE PACKAGE Consider the S8 or Z Packages for Alternate Source

ELECTRICAL CHARACTERISTICS

CURRENT SOURCE (Note 2) LM134-3,LM234-3 LM134-6, LM234-6 SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS DISET Set Current Error, V+ = 2.5V 100 mA £ ISET £ 1mA –1 –2% (Note 3) T j = 25°C Equivalent Temperature Error –3 –6 °C Ratio of Set Current to 100 mA £ ISET £ 1 m A 1 41 82 61 41 82 6 V– Current VMIN Minimum Operating Voltage 100 mA £ ISET £ 1mA 0.9 0.9 V DVIN with Input Voltage 100 mA £ ISET £ 1mA 5V £ V+ £ 30V 0.01 0.03 0.01 0.05 %/V Temperature Dependence of 100 mA £ ISET £ 1mA 0.98 1.02 0.97 1.03 Set Current (Note 4) Equivalent Slope Error –2 –3% CS Effective Shunt Capacitance 15 15 pF TEMPERATURE SENSOR (Note 2) LM134 LM334 SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS DISET Set Current Error, V+ = 2.5V 10 mA £ ISET £ 1mA 3 6 % (Note 3) 1mA < I SET £ 5mA 5 8 % 2mA £ ISET < 10mA8 1 2 % Ratio of Set Current to 10 mA £ ISET £ 1 m A 1 41 82 31 41 82 6 V– Current 1mA £ ISET £ 5mA 14 14 2mA £ ISET £ 10mA 1 82 3 1 82 6 VMIN Minimum Operating Voltage 2 mA £ ISET £ 100mA 0.8 0.8 V 100mA < ISET £ 1mA 0.9 0.9 V 1mA < ISET £ 5mA 1.0 1.0 V DVIN with Input Voltage 2 mA £ ISET £ 1mA 5V £ V+ £ VMAX (Note 5) 0.01 0.03 0.01 0.05 %/V 1mA < ISET £ 5mA 5V £ V £ VMAX (Note 5) 0.02 0.02 %/V Temperature Dependence of 25 mA £ ISET £ 1mA 0.96 1.04 0.96 1.04 Set Current (Note 4) CS Effective Shunt Capacitance 15 15 pF Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Unless otherwise specified, tests are performed at Tj = 25°C with pulse testing so that junction temperature does not change during test. Note 3: Set current is the current flowing into the V+ pin. It is determined by the following formula: ISET = 67.7mV/RSET (at 25°C). Set current error is expressed as a percent deviation from this amount. ISET increases at 0.336%/°C at Tj = 25°C. Note 4: ISET is nominally directly proportional to absolute temperature (°K). ISET at any temperature can be calculated from: ISET = IO (T/TO) where IO is ISET measured at TO (°K). Note 5: VMAX = 40V for LM134 and 30V for other grades.

Transient Response Voltage Across RSET Current Noise Turn-On Voltage Ratio of ISET to V– Current Operating Current vs Temperature TYPICAL PERFOR A CE CHARACTERISTICSUW FREQUENCY (Hz) 106 IMPEDANCE (Ω ) 107 108 109 100 1k 10k

134 G01

I = 100µA I = 10µA I = 1mA ISET (µA) 0.01SLEW RATE (V/µs) 0.1 1.0 1 100 1000

134 G02

0.001 10 10000 10µA 0µA 100µA 0µA 1mA 0mA ISET

134 G03

200µs INPUT 50µs 5µs TIME (*NOTE SCALE CHANGES FOR EACH CURRENT LEVEL) –10 –20 ∆ISET (%)

134 G04

2µs 50µs 10µs ISET = 1mA ISET = 100µA ISET = 10µA V+ TO V– = 5V ∆V = 0.4V tr, f = 500ns TIME (*NOTE SCALE CHANGES FOR EACH CURRENT LEVEL) TEMPERATURE (°C) –50 VOLTAGE (mV) 0 50 75 1314/15 G01 –25 25 100 125 FREQUENCY (Hz) CURRENT (pA/ÖHz) 100 10k 10 1k 10k

134 G06

ISET = 100µA ISET = 1mA ISET = 5mA ISET = 10µA V+ TO V– VOLTAGE 10µA ISET 1mA 10mA 0.4 0.8 1.2 1.0 1µA 0.6 1.4 RSET = 68Ω RSET = 680Ω RSET = 6.8k Tj = 25°C RSET = 14Ω 100µA ISET 10µA RATIO 100µA 1mA 10mA

134 G08

OPERATING CURRENT (µA) TEMPERATURE (°K) 500 400 300 200 100 400

134 G09

RSET = 226Ω 225 125 –75 –175 –275 TEMPERATURE (°C)

APPLICATIO S I FOR ATIOWU UU Basic Theory of Operation The equivalent circuit of the LM134 is shown in Figure 1. A reference voltage of 64mV is applied to the minus input of A1 with respect to the V– pin. A1 serves the drive to Q2 to keep the R pin at 64mV, independent of the value of RSET. Transistor Q1 is matched to Q2 at a 17:1 ratio so that the current flowing out of the V– pin is always 1/18 of the total current into the V+ pin. This total current is called ISET and is equal to: 64 18 67 7mV R mV RSET SET æ Łç ö æ Łç ö ł÷ = . Figure 1. The 67.7mV equivalent reference voltage is directly pro- portional to absolute temperature in degrees Kelvin (see curve, “Operating Current vs Temperature”). This means that the reference voltage can be plotted as a straight line going from 0mV at absolute zero temperature to 67.7mV at 298°K (25°C). The slope of this line is 67.7mV/298 = 227mV/°C. The accuracy of the device is specified as a percent error at room temperature, or in the case of the -3 and -6 devices, as both a percent error and an equivalent tem- perature error. The LM134 operating current changes at a percent rate equal to (100)(227mV/°C)/(67.7mV) = 0.336%/ °C at 25°C, so each 1% operating current error is equiva- lent to »3°C temperature error when the device is used as a temperature sensor. The slope accuracy (temperature coefficient) of the LM134 is expressed as a ratio com- pared to unity. The LM134-3, for instance, is specified at 0.98 to 1.02, indicating that the maximum slope error of RSET ISET 64mV R Q2Q1

134 F01

the device is –2% when the room temperature current is set to the exact desired value. Supply Voltage Slew Rate At slew rates above a given threshold (see curve), the LM134 may exhibit nonlinear current shifts. The slewing rate at which this occurs is directly proportional to ISET. At ISET = 10mA, maximum dv/dt is 0.01V/ms; at ISET = 1mA, the limits is 1V/ms. Slew rates above the limit do not harm the LM134, or cause large currents to flow. Thermal Effects Internal heating can have a significant effect on current regulation for ISET greater than 100mA. For example, each 1V increase across the LM134 at ISET = 1mA will increase junction temperature by »0.4°C in still air. Output current (ISET) has a temperature coefficient of »0.33%/°C, so the change in current due to temperature rise will be (0.4)(0.33) = 0.132%. This is a 10:1 degradation in regulation com- pared to true electrical effects. Thermal effects, therefore, must be taken into account when DC regulation is critical and I SET exceeds 100mA. Heat sinking of the TO-46 pack- age or the TO-92 leads can reduce this effect by more than 3:1. Shunt Capacitance In certain applications, the 15pF shunt capacitance of the LM134 may have to be reduced, either because of loading problems or because it limits the AC output impedance of the current source. This can be easily accomplished by buffering the LM134 with a FET, as shown in the applica- tions. This can reduce capacitance to less than 3pF and improve regulation by at least an order of magnitude. DC characteristics (with the exception of minimum input voltage) are not affected. Noise Current noise generated by the LM134 is approximately 4 times the shot noise of a transistor. If the LM134 is used as an active load for a transistor amplifier, input referred noise will be increased by about 12dB. In many cases, this is acceptable and a single stage amplifier can be built with a voltage gain exceeding 2000.

The sense voltage which determines the operating current of the LM134 is less than 100mV. At this level, thermo- couple or lead resistance effects should be minimized by locating the current setting resistor physically close to the device. Sockets should be avoided if possible. It takes only 0.7W contact resistance to reduce output current by 1% at the 1mA level. Start-Up Time The LM134 is designed to operate at currents as low as 1mA. This requires that internal biasing current be well below that level because the device achieves its wide operating current range by using part of the operating current as bias current for the internal circuitry. To ensure start-up, however, a fixed trickle current must be provided internally. This is typically in the range of 20nA to 200nA and is provided by the special ultralow I DDS FETs shown in the Schematic Diagrams as Q7 and Q8. The start-up time of the LM134 is determined by the IDSS of these FETs and the capacitor C1. This capacitor must charge to approxi- mately 500mV before Q3 turns on to start normal circuit operation. This takes as long as (500mV)(50pF)/(20nA) = 1.25ms for very low I DSS values. Using the LM134 as a Temperature Sensor Because it has a highly linear output characteristic, the LM134 makes a good temperature sensor. It is particularly useful in remote sensing applications because it is a current output device and is therefore not affected by long wire runs. It is easy to calibrate, has good long term stability and can be interfaced directly with most data acquisition systems, eliminating the expensive preampli- fiers required for thermocouples and platinum sensors. A typical temperature sensor application is shown in Figure␣ 2. The LM134 operating current at 25°C is set at 298mA by the 226W resistor, giving an output of 1mA/°K. The current flows through the twisted pair sensor leads to the 10k termination resistor, which converts the current output to a voltage of 10mV/ °K referred to ground. The voltage across the 10k resistor will be 2.98V at 25°C, with a slope of 10mV/ °C. The simplest way to convert this signal to a Centigrade scale is to subtract a constant 2.73V in software. Alternately, a hardware conversion can be used, as shown in Figure 3, using an LT1009 as a level shifter to offset the output to a Centigrade scale. The resistor (R SET) used to set the operating current of the LM134 in temperature sensing applications should have low temperature coefficient and good long term stability. A 30ppm/°C drift in the resistor will change the slope of the temperature sensor by 1%, assuming that the resistor is at the same temperature as the sensor, which is usually the case since the resistor should be located physically close to the LM134 to prevent errors due to wire resistance. A long term shift of 0.3% in the resistor will create a 1 °C temperature error. The long term drift of the LM134 is typically much better than this, so stable resistors must be used for best long term performance. Calibration of the LM134 as a temperature sensor is extremely easy. Referring to Figure 2, calibration is achieved by trimming the termination resistor. This theoretically trims both zero and slope simultaneously for Centigrade and Fahrenheit applications. The initial errors in the LM134 are directly proportional to absolute temperature, just like the actual output. This allows the sensor to be trimmed at any temperature and have the slope error be corrected at the same time. Residual slope error is typically less than 1% after this single trim is completed. Figure 2 Kelvin Temperature Sensor TO DATA ACQUISITION SYSTEM 10mV/°K 9.53k CALIBRATE 134 F02 R LM234-3 RSET 226Ω I = 1µA/°K VS ‡ 5V APPLICATIO S I FOR ATIOWU UU

Figure 3. Centigrade Temperature Sensor

134 F03

adjust the 1k trimmer for proper output.

134 F04

Figure 4. Centigrade Temperature Sensor with 2 Point Trim

134 TA03

5 OR MORE BY INSERTING AN EQUIVALENT RESISTOR IN

134 TA04

OBTAIN ZERO DRIFT. I+ »2 ISET.

134 TA02

R LM334 VIN 100Ω 300Ω 15k 4.5k 2N4250 VOUT = 10mV/°K ZOUT ≤ 2ΩC1 0.0022 TA07 RLM334 VIN ‡ VREF + 200mV 120Ω 1.5k 2N4250 VOUT = VZ + 64mV AT 25°C IOUT ≤ 3mA 0.1 LT1009VZ TA05 R LM334 VIN –VIN RSET R1* C1* *SELECT R1 AND C1 FOR OPTIMUM STABILITY 2N2905 TA08 RLM334 VIN –VIN RSET 68k 1µA LM4250 RLM134 0.001 100k VIN ‡ 1.8V VOUT = 1.2V IOUT ≤ 200µA 2N4250 33k 1N457 R1* »6k R2* 680Ω SELECT RATIO OF R1 TO R2 FOR ZERO TEMPERATURE DRIFT LM134 AND DIODE SHOULD BE ISOTHERMAL TA09 TA10 RLM334 VIN VOUT RSET VZ Higher Output Current Low Output Impedance Thermometer Low Input Voltage Reference Driver Micropower Bias 1.2V Regulator with 1.8V Minimum Input Zener Biasing Alternate Trimming Technique Buffer for Photoconductive Cell High Precision Low TC Current Source R R1* LM334 RSET TA11 VIN –VIN *FOR –10% ADJUSTMENT, SELECT RSET 10% HIGH AND MAKE R1 » 3RSET R LM334 TA12 1.5V 1.37V TA13 RLM334 R2* 6.8k ISET ‡ 50µA LT1004-1.2 (1.235V) *ISET = + 10µA ISET TC = 0.016%/°C + 33nA/°C REGULATION » 0.001%/V

Precision 10nA Current Source Micropower 5V Reference FET Cascoding for Low Capacitance and/or Ultrahigh Output Impedance WSCHE ATIC DIAGRA W Q7 Q8 Q5Q4 Q6 Q1Q2 R 50pF 134 SD IO R 2.7k 226k 100MΩ LM134 LT1004-1.2 15V –15V 15V LT1008 BUFFERED VOLTAGE OUTPUT 200pF I O = 10nA ZO ‡ 1012Ω COMPLIANCE = –14V TO 12.5V TA14 RLM334 TA15 LM4250 22MLT1004-1.2 (1.235V) 5.6k 3.01M 1%150pF VIN = 6.5V TO 15V VOUT = 5V R LM334 RSET ISET ISET VIN –VIN Q1* R LM334 RSET TA16 VIN –VIN Q2* *SELECT Q1 OR Q2 TO ENSURE AT LEAST 1V ACROSS THE LM134. VP (1 – ISET/IDSS) ‡ 1.2V.

0.016 – 0.021** (0.406 – 0.533) DIA 0.025 (0.635) MAX 0.085 – 0.105 (2.159 – 2.667) 0.500 (12.700) MIN 0.178 – 0.195 (4.521 – 4.953) 0.209 – 0.219 (5.309 – 5.537) 0.100 (2.540) TYP 45° H02/03(TO-46) 1098 0.050 (1.270) TYP 0.050 (1.270) TYP 0.028 – 0.048 (0.711 – 1.219) 0.036 – 0.046 (0.914 – 1.168) FOR 3-LEAD PACKAGE ONLY REFERENCE PLANE * LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE AND 0.045" BELOW THE REFERENCE PLANE FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS 0.016 – 0.024 (0.406 – 0.610) PIN 1 0.050 (1.27) BSC 0.060 – 0.005 (1.524– 0.127) DIA 0.90 (2.286) NOM 0.180 – 0.005 (4.572 – 0.127) 0.180 – 0.005 (4.572 – 0.127) 0.500 (12.70) MIN 0.050 (1.270) MAX UNCONTROLLED LEAD DIMENSION 0.016 – 0.003 (0.406 – 0.076) NOM 0.015 – 0.002 (0.381 – 0.051) 0.060 – 0.010 (1.524 – 0.254) 10° NOM 0.140 – 0.010 (3.556 – 0.127) Z3 (TO-92) 0401 0.098 +016/–0.04 (2.5 +0.4/–0.1)

2 PLCS

REFER TO TAPE AND REEL SECTION OF LTC DATA BOOK FOR ADDITIONAL INFORMATION PACKAGE DESCRIPTIO U Z Package 3-Lead Plastic TO-92 (Similar to TO-226) (Reference LTC DWG # 05-08-1410) H Package 2-Lead and 3-Lead TO-46 Metal Can (Reference LTC DWG # 05-08-1340) OBSOLETE PACKAGE

0.016 – 0.050 (0.406 – 1.270) 0.010 – 0.020 0°– 8° TYP 0.008 – 0.010 (0.203 – 0.254) SO8 1298 0.053 – 0.069 (1.346 – 1.752) 0.014 – 0.019 (0.355 – 0.483) TYP 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSC 1 2 3 4 0.150 – 0.157** (3.810 – 3.988) 8 7 6 5 0.189 – 0.197* (4.801 – 5.004) 0.228 – 0.244 (5.791 – 6.197) DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 l FAX: (408) 434-0507 l www.linear.com ª LINEAR TECHNOLOGY CORPORATION 1991 134sc LT/CP 1001 1.5K REV C • PRINTED IN USA TYPICAL APPLICATIO SU In-Line Current Limiter Generating Negative Output Impedance Ground Referred Fahrenheit Thermometer V–V+ R RSET LM334 TA17 VIN OP AMP C1* *USE MINIMUM VALUE REQUIRED TO ENSURE STABILITY OF PROTECTED DEVICE. THIS MINIMIZES INRUSH CURRENT TO A DIRECT SHORT. R LM334 RSET R1* TA18 VIN –VIN *ZOUT » –16 • R1(R1/VIN MUST NOT EXCEED ISET). R LM334 100Ω 8.25k 56k R5** R3* TA19 VIN VOUT = 10mV/°F 10°F ≤ T ≤ 250°F 0.01 2N4250 VIN ‡ 3V LT1009 2.5V* *SELECT R3 = VREF/583µA **SELECT FOR 1.2mA