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LM134-LM234 LM334
THREE TERMINAL ADJUSTABLE CURRENT SOURCES
.OPERATESf .0. .PROGRAMMABLEf .3%I
DESCRIPTION
rom 1V to 40V 02% V CURRENT REGULATION rom 1A to 10mA NITIAL ACCURACY
Z TO92 (Plastic Package)
The LM134/LM234/LM334 are 3-terminal adjustable current sources characterized by : - an operating current range of 10000 : 1 - an excellent current regulation - a wide dynamic voltage range of 1V to 40V The current is determined by an external resistor without requiring other external components. Reverse voltages of up to 20V will only draw a current of several microamperes. This enables the circuit to operate as a rectifier and as a source of current in a.c. applications. For the LM134/LM234/LM334, the voltage on the control pin is 64mV at +25oC and is directly proportionalto the absolute temperature (oK). The simplest external resistor connection generates a current with 0.33%/oC temperature dependence. Zero drift can be obtainedby adding an additionalresistor and a diode to the external circuit. PIN CONNECTIONS
TO92 (Bottom view)
D SO8 (Plastic Micropackage)
ORDER CODES
Part Number LM134 LM234 LM334 Example : LM134Z Temperature Range -55oC, +125oC -25 C, +100 C 0 C, +70 C
o o o o
Package Z * * * D * * *
SO8 (Top view)
NC NC
8
V+
2
7
V6
NC 5
AD J
1
V
-
3
1 ADJ
2 NC
3 NC
4 V+
October 1997
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LM134-LM234-LM334
SCHEMATIC DIAGRAM
V
Q4 Q5 Q6
Q3
C1 50pF
Q2
Q1
ADJ V
ABSOLUTE MAXIMUM RATING
Symbol Voltage V to V Forward Reverse VADJISET Ptot Tstg Toper Set Current Power Dissipation Storage Temperature Range Operating Free-air Temperature Range LM134 LM234 LM334
+ -
Parameter
LM134 - LM234 40 20 5 10 400 -65 to +150 -55 to +125 -25 to +100 0 to +70
LM334 30 20 5 10 400
Unit V
ADJ Pin to V - Voltage
V mA mW
o o
C C
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LM134-LM234-LM334
ELECTRICAL CHARACTERISTICS Tj = +25oC with pulse testing so that junction temperature does not change during testing (unless otherwise specified)
Parameter Set Current Error (V = +2.5V) - (note 1) 10A ISET 1mA 1mA ISET 5mA 2A ISET 10A Ratio of Set Current to V Current 10A ISET 1mA 1mA ISET 5mA 2A ISET 10A Minimum Operating Voltage 2A ISET 100A 100A ISET 1mA 1mA ISET 5mA Average change in set current with input voltage 2A ISET 1mA + +1.5V V +5V +5V V+ +40V 1mA ISET 5mA + +1.5V V + +5V + +5V V +40V Temperature Dependence of set current - (note 2) 25A ISET 1mA Effective Shunt Capacitance
Notes :
- +
LM134 - LM234 Min. Typ. Max. 3 5 8 14 18 14 14 0.8 0.9 1 23 14 Min.
LM334 Typ. Max. 6 8 12 18 14 14 0.8 0.9 1 26
Unit %
V
%/V 0.02 0.01 0.03 0.02 0.96 T T 15 1.04 T 0.96 T 0.05 0.03 0.02 0.01 0.03 0.02 T 15 1.04 T pF 0.1 0.05
1. Set current is the current flowing into theV + pin. It is determined by the following formula Iset = 67.7mV/Rset (Tj = +25oC). Set current error is expressed as a percent deviation from this amount. 2. Iset is directly proportional to absolute temperature (oK). Iset at any temperature can be calculated from Iset = IO (T/TO) where IO is Iset measured at TO (oK).
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LM134-LM234-LM334
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LM134-LM234-LM334
APPLICATION HINT SLEW RATE At slew rates above a threshold (see curve) the LM134, LM234, LM334 can have a non-linear current characteristic. The slew rate at which this takes place is directly proportional to Iset. At Iset = 10A, dv/dt max. = 0.01V/S ; at Iset = 1mA, dv/dt max. = 1V/S. Slew rates of more than 1V/S do not damage the circuit nor do they produce high currents. THERMAL EFFECTS Internal heating can have a significant effect on current regulation for an Iset above 100A. For example, each increase of 1V in the voltage across the LM134 at Iset = 1mA will increase the junction temperature by 0.4oC (in still air). The output current (Iset) has a temperature coefficient of about 0.33%/oC. Thus the change in current due to the increase in temperature will be (0.4) (0.33) = 0.132%. This is a degradation of 10 : 1 in regulation versus the true electrical effects. Thermal effects should be taken into account when d.c. regulation is critical and Iset is higher than 100A. The dissipation of the connectionsof CB-97 packagecan reduce this thermal effect by a coefficient of more than 3. SHUNT CAPACITANCE In certain applications, the 15pF value for the shunt capacitance should be reduced : - because of loading problems, - because of limitation of the output impedance of the current source in a.c. applications. This reduction of the capacitance can be easily carried out by adding a FET as indicatedin the typical applications. The value of this capacitance can be reduced by at least 3pF and regulation can be improved by an order of magnitude without any modificationof the d.c. characteristics (except for the minimum input voltage). NOISE The current noise produced by LM134, LM234, LM334 is about 4 times that of a transistor. If the LM134, LM234, LM334 is utilized as an active load for a transistor amplifier, the noise at the input will increase by about 12dB. In most cases this is acceptable, and a single amplifier can be built with a voltage gain higher than 2000. LEAD RESISTANCE The sense voltage which determines the current of the LM134, LM234, LM334, is less than 100mV. At this level, the effects of the thermocouple and the connection resistance should be reduced by locating the current setting resistor close to the device. Do not use sockets for the ICs. A contact resistance of 0.7 is sufficient to decrease the output current by 1% at the 1mA level. SENSING TEMPERATURE The LM134, LM234, LM334 are excellent remote controlled temperature sensors because their operation as sources of current preserves their accuracy even in the case of long connecting wires. The output current is directly proportional to the absolute temperature in degrees Kelvin according to the following equation. (227V/oK) (T) Rset The calibration of the LM134, LM234, LM334 is simplified by the fact that most of the initial accuracy is due to gain limitation (slope error) and not an offset. Gain adjustment is a one point trim because the output of the device extrapolates to zero at 0oK. Iset =
Initial output c
I set
b c' a a' b'
Desired output
0K
T1
T2
T3
This particularity of the LM134, LM234, LM334 is illustrated in the above diagram. Line abc represents the sensor current before adjustment and line a'b'c' represents the desired output. An adjustment of the gain provided at T2 will move the output from b to b' and will correct the slope at the same time so that the output at T1 and T3 will be correct. This gain adjustment can be carried out by means of Rset or the load resistor utilized in the circuit. After adjustment, the slope error should be less than 1%. A low temperaturecoefficient for Rset is necessary to keep this accuracy. A 33ppm/oC temperature drift of Rset will give an error of 1% on the slope because the resistance follows the same temperature variations as the LM134, LM234, LM334. Three wires are required to isolate Rset from the LM134, LM234, LM334. Since this solution is not recommended. Metal-film resistors with a drift less than 20ppm/oC are now available. Wirewound resistors can be utilized when very high stability is required.
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LM134-LM234-LM334
TYPICAL APPLICATIONS Figure 1 : Basic 2-terminal Current Source
Figure 2 :
Alternate Trimming Technique
Vi V ADJ V R set R1*
Vi V ADJ V R set
Vi
Vi
* For 10% adjustment, select Rset 10% high and make R1 3 Rset
Figure 3 : Terminating Remote Sensor for Voltage Output
Figure 4 : Zero Temperature Coefficient Current Source
Vi V ADJ V R set
Vi V
i
ADJ V R set
VO RL
D1 1N 457
R1* 10 R set Vi
V O = ( Iset) (R L) = 10mV/ K R set = 230 R L = 10k
O
* Select ratio of R1 to R set to obtain zero dri ft i+ 2I set
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LM134-LM234-LM334
Figure 5 : Low Output Impedance Thermometer
Vi > 4.8V V ADJ V R1
V
FIgure 6 : Low Output Impedance Thermometer
Vi
R3 VO
R1 R2
C1 R2
C1
ADJ
VO R3
R1 = 230, 1% V O = 10mV/ oK R2 = 10k, 1% ZO 100 R3 = 600 Output i mpedance of the LM134, LM234, LM334 at the - Ro where R o is the equiva"A DJ" pin is approximately 16 lent external resi stance connected to the V- pin. T his negative resi stance can be reduced by a factor of 5 or more by i nserting an equi valent resistor in seri es with the output
V
R1 = 15k R2 = 300 R3 = 100 R4 = 4.5k C1 = 2.2nF V O = 10mV/ O K ZO 2
R4
Figure 7 : Micropower Bias
Figure 8 : Low Input Voltage Reference Driver
Vi
Vi R1
UA776 1A V ADJ R set V Vi
R set = 68k
C1 2N2905 VO V ADJ V
R1 = 1.5k R2 = 120 C1 = 0.1F IO 3mA V I+ V ref +200mV V O = VZ +64mV (+25 oC)
LM136
R2
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LM134-LM234-LM334
Figure 9 : In-line Current Limiter Figure 10 : Fet Cascading for Low Capacitance
Vi
R set ADJ Vi V V C1*
Iset
Q* V > 1.2V DS V ADJ V
R set
OP AMP
Vi
* Use minim um value required to ensure stabil ity of protected circuit * Sel ect Q to ensure at least 1V across the LM134, LM234, LM334. V p (1 - Iset/ID SS ) 1.2V
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LM134-LM234-LM334
PACKAGE MECHANICAL DATA 8 PINS - PLASTIC MICROPACKAGE (SO)
Dimensions A a1 a2 a3 b b1 C c1 D E e e3 F L M S
Min. 0.1 0.65 0.35 0.19 0.25 4.8 5.8
Millimeters Typ.
Max. 1.75 0.25 1.65 0.85 0.48 0.25 0.5 45 (typ.) 5.0 6.2
o
Min. 0.004 0.026 0.014 0.007 0.010 0.189 0.228
Inches Typ.
Max. 0.069 0.010 0.065 0.033 0.019 0.010 0.020 0.197 0.244
1.27 3.81 3.8 0.4 4.0 1.27 0.6 8 (max.)
o
0.050 0.150 0.150 0.016 0.157 0.050 0.024
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SO8.TBL
PM-SO8.EPS
LM134-LM234-LM334
PACKAGE MECHANICAL DATA 3 PINS - PLASTIC PACKAGE TO92
Dimensions L B O1 C K O2 a
Min. 3.2 4.45 4.58 12.7 0.407 0.35
Millimeters Typ. 1.27 3.7 5.00 5.03 0.5
Max. 4.2 5.2 5.33 0.508
Min. 0.126 0.1752 0.1803 0.5 0.016 0.0138
Inches Typ. 0.05 0.1457 0.1969 0.198 0.0197
Max. 0.1654 0.2047 0.2098 0.02
TO92.TBL ORDER CODE :
Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specification mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical componen ts in life support devices or systems without express written approval of SGS-THOMSON Microelectronics. (c) 1997 SGS-THOMSON Microelectronics - Printed in Italy - All Rights Reserved SGS-THOMSON Microelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco The Netherlands - Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A.
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PM-TO92.IMG

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