LM134_NationalSemiconductor_elenota.pl.pdf

March 2005

LM134/LM234/LM334

3-Terminal Adjustable Current Sources

General Description

The LM134/LM234/LM334 are 3-terminal adjustable current

sources featuring 10,000:1 range in operating current, excel-

lent 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 supply connections. In ad-

dition, 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 abso-

lute temperature (˚K). The simplest one external resistor

connection, then, generates a current with

LED driver, and temperature sensing. The LM234-3 and

LM234-6 are specified as true temperature sensors with

guaranteed initial accuracy of ± 3˚C and ± 6˚C, respectively.

These devices are ideal in remote sense applications be-

cause 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.

+0.33%/˚C tem-

perature 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,

≈

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

n ± 3% initial accuracy

Connection Diagrams

SO-8

Surface Mount Package

SO-8 Alternative Pinout

Surface Mount Package

00569724

Order Number LM334M or LM334MX

See NS Package Number M08A

00569725

Order Number LM334SM or LM334SMX

See NS Package Number M08A

TO-46

Metal Can Package

TO-92 Plastic Package

00569712

00569710

Bottom View

Order Number LM334Z, LM234Z-3 or LM234Z-6

See NS Package Number Z03A

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.

V + to V − Forward Voltage

LM134/LM234/LM334

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

40V

SO Package

Vapor Phase (60 sec.)

LM234-3/LM234-6

30V

215˚C

V + to V − Reverse Voltage

20V

Infrared (15 sec.)

220˚C

R Pin to V − Voltage

See AN-450 “Surface Mounting Methods and Their Effect on

Product Reliability” (Appendix D) for other methods of sol-

dering surface mount devices.

Set Current

10 mA

Power Dissipation

400 mW

ESD Susceptibility (Note 6)

2000V

Operating Temperature Range (Note

LM134

−55˚C to +125˚C

Electrical Characteristics (Note 2)

Parameter

Conditions

LM134/LM234

LM334

Units

Min Typ Max Min Typ Max

Set Current Error, V + =2.5V,

10µA

≤

I SET ≤

1mA

6 %

(Note 3)

1mA < I SET ≤ 5mA

8 %

2µA

≤

I SET < 10µA

12 %

Ratio of Set Current to

100µA

≤

I SET ≤

1mA 14

Bias Current

1mA ≤ I SET ≤ 5mA

2µA

≤

I SET

≤

100 µA

Minimum Operating Voltage

2µA

≤

I SET ≤

100µA

0.8

100µA < I SET ≤ 1mA

0.9

1mA < I SET ≤ 5mA

1.0

Average Change in Set Current 2µA

≤

I SET ≤

1mA

with Input Voltage

1.5 ≤ V +

≤ 5V

0.02 0.05

0.02

0.1 %/V

≤

V +

≤

40V

0.01 0.03

0.01 0.05 %/V

1mA < I SET ≤ 5mA

1.5V

≤

0.03

%/V

≤

40V

0.02

%/V

Temperature Dependence of

25µA ≤ I SET ≤ 1mA 0.96T T 1.04T 0.96T T 1.04T

Set Current (Note 4)

Effective Shunt Capacitance

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 j = 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. For the Basic 2-Terminal Current Source circuit shown on the first page of this data sheet. I SET is

determined by the following formula: I SET = 67.7 mV/R SET ( @ 25˚C). Set current error is expressed as a percent deviation from this amount. I SET increases at

0.336%/˚C @ T j = 25˚C (227 µV/˚C).

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Electrical Characteristics (Note 2) (Continued)

Note 4: I SET is directly proportional to absolute temperature (˚K). I SET at any temperature can be calculated from: I SET =I o (T/T o ) where I o is I SET measured at T o

(˚K).

Note 5: For elevated temperature operation, T J max is:

LM134

150˚C

LM234

125˚C

LM334

100˚C

Thermal Resistance

TO-92

TO-46 SO-8

θ ja (Junction to

Ambient)

180˚C/W (0.4" leads) 440˚C/W 165˚C/W

160˚C/W (0.125"

leads)

θ jc (Junction to Case)

N/A

32˚C/W 80˚C/W

Note 6: Human body model, 100pF discharged through a 1.5k

Ω

resistor.

Electrical Characteristics (Note 2)

Parameter

Conditions

LM234-3

LM234-6

Units

Min Typ Max Min Typ Max

Set Current Error, V + =2.5V,

100µA

≤

I SET ≤

1mA

± 1

± 2 %

(Note 3)

T J = 25˚

Equivalent Temperature Error

± 3

± 6

˚C

Ratio of Set Current to

100µA ≤ I SET ≤ 1mA 14

Bias Current

Minimum Operating Voltage

100µA I SET ≤

1mA

0.9

Average Change in Set Current 100µA

≤

I SET ≤

1mA

with Input Voltage

1.5

≤

V +

≤

0.02 0.05

0.02 0.01 %/V

5V ≤ V +

≤ 30V

0.01 0.03

0.01 0.05 %/V

Temperature Dependence of

100µA ≤ I SET ≤ 1mA 0.98T T 1.02T 0.97T T 1.03T

Set Current (Note 4) and

Equivalent Slope Error

± 2

± 3 %

Effective Shunt Capacitance

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Typical Performance Characteristics

Output Impedance

Maximum Slew Rate

Linear Operation

00569730

00569731

Start-Up

Transient Response

00569732

00569733

Voltage Across R SET (V R )

Current Noise

00569734

00569735

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Typical Performance Characteristics (Continued)

Turn-On Voltage

Ratio of I SET to I BIAS

00569729

00569703

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 con-

tact resistance.

where n is the ratio of I SET to I BIAS as specified in the

Electrical Characteristics Section and shown in the graph.

Since n is typically 18 for 2µA ≤ I SET ≤ 1mA, the equation can

be further simplified to

CALCULATING R SET

The total current through the LM134 (I SET ) is the sum of the

current going through the SET resistor (I R ) and the LM134’s

bias current (I BIAS ), as shown in Figure 1 .

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 SET .At

I SET = 10µA, maximum dV/dt is 0.01V/µs; at I SET = 1mA, the

limit is 1V/µs. 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 I SET greater than 100µA. For example, each

1V increase across the LM134 at I SET = 1 mA will increase

junction temperature by

≈

00569727

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

compared to true electrical effects. Thermal effects, there-

fore, 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.

≈

FIGURE 1. Basic Current Source

A graph showing the ratio of these two currents is supplied

under Ratio of I SET to I BIAS in the Typical Performance

Characteristics section. The current flowing through R SET is

determined by V R , which is approximately 214µV/˚K (64

mV/298˚K

∼

214µV/˚K).

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 limits the AC output impedance 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

Since (for a given set current) I BIAS is simply a percentage of

I SET , the equation can be rewritten

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0.4˚C in still air. Output current

(I SET ) has a temperature coefficient of

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