NSC LM234Z-6, LM234Z-3, LM134H, LM234H Datasheet

LM134/LM234/LM334 3-Terminal Adjustable Current Sources

March 2000

General Description

The LM134/LM234/LM334 are 3-terminal adjustable current sources featuring10,000:1 range in operating current, excellent current regulation and a wide dynamic voltage range of 1V to 40V. Current is established with one external resistor and no other parts are required. Initial current accuracy is

3%. The LM134/LM234/LM334 are true floating current sources with no separate power supplyconnections. Inaddition, reverse applied voltages of up to 20V will draw only a few dozen microamperes of current, allowing the devices to act as both a rectifier and current source in AC applications.

The sense voltage used to establish operating current in the LM134 is 64mV at 25˚C and is directly proportional to absolute temperature (˚K). The simplest one external resistor connection, then, generates a current with ≈+0.33%/˚C temperature dependence. Zero drift operation can be obtained by adding one extra resistor and a diode.

Applications for the current sources include bias networks, surge protection, low power reference, ramp generation,

Connection Diagrams

SO-8

Surface Mount Package

SO-8 Alternative Pinout Surface Mount Package

LED driver, and temperature sensing. The LM234-3 and LM234-6 are specified as true temperature sensors with guaranteed initial accuracy of These devices are ideal in remote sense applications because series resistance in long wire runs does not affect accuracy. In addition, only 2 wires are required.

The LM134 is guaranteed over a temperature range of

−55˚C to +125˚C, the LM234 from −25˚C to +100˚C and the LM334 from 0˚C to +70˚C. These devices are available in TO-46 hermetic, TO-92 and SO-8 plastic packages.

3˚C and±6˚C, respectively.

Features

n Operates from 1V to 40V n 0.02%/V current regulation n Programmable from 1µA to 10mA n True 2-terminal operation n Available as fully specified temperature sensor

3% initial accuracy

TO-46

Metal Can Package

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Order Number LM334M or

LM334MX

See NS Package Number M08A

Order Number LM334Z, LM234Z-3 or LM234Z-6

Order Number LM334SM or

LM334SMX

See NS Package Number M08A

TO-92 Plastic Package

Bottom View

See NS Package Number Z03A

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V−Pin is electrically connected to case.

Bottom View

Order Number LM134H,

LM234H or LM334H

See NS Package

Number H03H

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

to V−Forward Voltage

LM134/LM234/LM334 40V

LM134/LM234/LM334

LM234-3/LM234-6 30V

to V−Reverse Voltage 20V

V R Pin to V

−

Voltage 5V Set Current 10 mA Power Dissipation 400 mW

LM234/LM234-3/LM234-6 −25˚C to +100˚C LM334 0˚C to +70˚C

Soldering Information

TO-92 Package (10 sec.) 260˚C TO-46 Package (10 sec.) 300˚C SO Package

Vapor Phase (60 sec.) 215˚C Infrared (15 sec.) 220˚C

See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” (Appendix D) for other methods of soldering surface mount devices.

ESD Susceptibility (Note 6) 2000V Operating Temperature Range (Note 5)

LM134 −55˚C to +125˚C

Electrical Characteristics (Note 2)

Parameter Conditions LM134/LM234 LM334 Units

Set Current Error, V (Note 3) 1mA

Ratio of Set Current to 100µA ≤ I Bias Current 1mA ≤ I

Minimum Operating Voltage 2µA ≤ I

=2.5V, 10µA ≤ I

2µA ≤ I

2µA≤I

100µA

≤ 1mA 3 6 %

SET

≤ 5mA 5 8 %

SET

10µA 8 12 %

SET

≤ 1mA 14 18 23 14 18 26

SET

≤ 5mA 14 14

SET

≤100 µA 18 23 18 26

SET

≤ 100µA 0.8 0.8 V

SET

≤

SET

1mA

≤ 5mA 1.0 1.0 V

SET

Average Change in Set Current 2µA ≤ I with Input Voltage 1.5 ≤ V

5V ≤ V 1mA

≤ 1mA

SET +

≤ 5V 0.02 0.05 0.02 0.1 %/V

≤ 40V 0.01 0.03 0.01 0.05 %/V

≤ 5mA

SET

1.5V ≤ V ≤ 5V 0.03 0.03 %/V 5V ≤ V ≤ 40V 0.02 0.02 %/V

Temperature Dependence of 25µA ≤ I

≤ 1mA 0.96T T 1.04T 0.96T T 1.04T

SET

Set Current (Note 4) Effective Shunt Capacitance 15 15 pF

Note 1: .“Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits.

Note 2: Unless otherwise specified, tests are performed at T Note 3: Set current is thecurrentflowingintotheV

by the following formula: I = 25˚C (227 µV/˚C).

Note 4: I (˚K).

Note 5: For elevated temperature operation, T

is directly proportional to absolute temperature (˚K). I

SET

LM134 150˚C LM234 125˚C LM334 100˚C

= 67.7 mV/R

SET

pin. For the Basic 2-TerminalCurrentSourcecircuitshownonthefirst page of this data sheet. I

(@25˚C). Set current error is expressed as a percent deviation from this amount. I

SET

max is:

= 25˚C with pulse testing so that junction temperature does not change during test

SET

Min Typ Max Min Typ Max

0.9 0.9 V

SET

at any temperature can be calculated from: I

SET=Io

(T/To) where Iois I

increases at 0.336%/˚C@T

SET

measured at T

SET

is determined

Thermal Resistance TO-92 TO-46 SO-8

(Junction to Ambient) 180˚C/W (0.4" leads) 440˚C/W 165˚C/W

160˚C/W (0.125" leads)

(Junction to Case) N/A 32˚C/W 80˚C/W

Note 6: Human body model, 100pF discharged through a 1.5kΩ resistor.

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Electrical Characteristics (Note 2)

Parameter Conditions LM234-3 LM234-6 Units

Set Current Error, V

=2.5V, 100µA ≤ I

SET

≤

1mA

(Note 3) T

= 25˚ Equivalent Temperature Error Ratio of Set Current to 100µA ≤ I

SET

≤

1mA Bias Current Minimum Operating Voltage 100µA I Average Change in Set Current 100µA ≤ I

≤ 1mA 0.9 0.9 V

SET

≤

SET

1mA

5V ≤ V

≤ 5V 0.02 0.05 0.02 0.01 %/V

≤ 30V 0.01 0.03 0.01 0.05 %/V

≤

SET

with Input Voltage 1.5 ≤ V

Temperature Dependence of 100µA ≤ I

1mA Set Current (Note 4) and Equivalent Slope Error Effective Shunt Capacitance 15 15 pF

Min Typ Max Min Typ Max

6˚C

14 18 26 14 18 26

0.98T T 1.02T 0.97T T 1.03T

LM134/LM234/LM334

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Typical Performance Characteristics

Output Impedance

LM134/LM234/LM334

Start-Up

Maximum Slew Rate Linear Operation

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Transient Response

Voltage Across R

SET(VR

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)

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Current Noise

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Typical Performance Characteristics (Continued)

LM134/LM234/LM334

Turn-On Voltage

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Application Hints

The LM134 has been designed for ease of application, but a general discussion of design features is presented here to familiarize the designer with device characteristics which may not be immediately obvious. These include the effects of slewing, power dissipation, capacitance, noise, and contact resistance.

CALCULATING R

The total current through the LM134 (I current going through the SET resistor (I bias current (I

SET

), as shown in

BIAS

SET

Figure 1

) is the sum of the ) and the LM134’s

Ratio of I

where n is the ratio of I

SET

to I

BIAS

SET

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to I

as specified in the Elec-

BIAS

trical Characteristics Section and shown in the graph. Since n is typically 18 for 2µA ≤ I

≤ 1mA, the equation can be

SET

further simplified to

for most set currents.

SLEW RATE

At slew rates above a given threshold (see curve), the LM134 may exhibit non-linear current shifts. The slewing rate at which this occurs is directly proportional to I I

= 10µA, maximum dV/dt is 0.01V/µs; at I

SET

limit is 1V/µs. Slew rates above the limit do not harm the LM134, or cause large currents to flow.

.At

SET

= 1mA, the

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FIGURE 1. Basic Current Source

A graph showing the ratio of these two currents is supplied under Ratio of I Characteristics section. The current flowing through R determined by V

to I

SET

, which is approximately 214µV/˚K (64 mV/

in the Typical Performance

BIAS

SET

298˚K ∼ 214µV/˚K).

Since (for a given set current) I I

, the equation can be rewritten

SET

is simply a percentage of

BIAS

THERMAL EFFECTS

Internal heating can have a significant effecton currentregulation for I crease across the LM134 at I tion temperature by ≈0.4˚C in still air. Output current (I

greater than 100µA. For example, each 1V in-

SET

= 1 mA will increase junc-

SET

) has a temperature coefficient of≈0.33%/˚C, sothe changein current due to temperature rise will be (0.4) (0.33) = 0.132%. This is a 10:1 degradation in regulation compared to true electrical effects. Thermal effects, therefore, must be taken into account when DC regulation is critical and I

SET

exceeds 100µA. Heat sinking of the TO-46 package or the TO-92 leads can reduce this effect by more than 3:1.

SHUNT CAPACITANCE

In certain applications, the 15 pF shunt capacitance of the LM134 may have to be reduced, either because of loading problems or because it limitsthe AC outputimpedance of the current source. This can be easily accomplished by buffering the LM134 with an FET as shown in the applications. This can reduce capacitance to less than 3 pF and improve regulation by at least an order of magnitude. DC characteristics (with the exception of minimum input voltage), are not affected.

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