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

+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,

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.

Features

Operates from 1V to 40V

0.02%/V current regulation

Programmable from 1µA to 10mA

True 2-terminal operation

Available as fully specified temperature sensor

3% initial accuracy

Connection Diagrams

SO-8

Surface Mount Package

DS005697-24

Order Number LM334M or

LM334MX

See NS Package Number M08A

SO-8 Alternative Pinout

Surface Mount Package

DS005697-25

Order Number LM334SM or

LM334SMX

See NS Package Number M08A

TO-46

Metal Can Package

DS005697-12

Pin is electrically connected to case.

Bottom View

Order Number LM134H,

LM234H or LM334H

See NS Package

Number H03H

TO-92 Plastic Package

DS005697-10

Bottom View

Order Number LM334Z, LM234Z-3 or LM234Z-6

See NS Package Number Z03A

March 2000

LM134/LM234/LM334

3-T
erminal

Adjustable

Current

Sources

DS005697

www.national.com

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

LM234-3/LM234-6

30V

to V

Reverse Voltage

20V

R Pin to V

Voltage

Set Current

10 mA

Power Dissipation

400 mW

ESD Susceptibility (Note 6)

2000V

Operating Temperature Range (Note 5)

LM134

-55°C to +125°C

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 sol-
dering surface mount devices.

Electrical Characteristics

(Note 2)

Parameter

Conditions

LM134/LM234

LM334

Units

Min

Typ

Max

Min

Typ

Max

Set Current Error, V

=2.5V,

10µA

SET

1mA

(Note 3)

1mA

SET

5mA

2µA

SET

10µA

Ratio of Set Current to

100µA

SET

1mA

Bias Current

1mA

SET

5mA

2 µA

SET

100 µA

Minimum Operating Voltage

2µA

SET

100µA

0.8

100µA

SET

1mA

0.9

1mA

SET

5mA

1.0

Average Change in Set Current

2µA

SET

1mA

with Input Voltage

1.5

0.02

0.05

0.02

0.1

%/V

40V

0.01

0.03

0.01

0.05

%/V

1mA

SET

5mA

1.5V

0.03

%/V

40V

0.02

%/V

Temperature Dependence of

25µA

SET

1mA

0.96T

1.04T

0.96T

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

= 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

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

= 25°C (227 µV/°C).

Note 4: I

SET

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

SET

at any temperature can be calculated from: I

SET

= I

(T/T

) where I

is I

SET

measured at T

(°K).

Note 5: For elevated temperature operation, T

max is:

LM134

150°C

LM234

125°C

LM334

100°C

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 1.5k

resistor.

LM134/LM234/LM334

www.national.com

Electrical Characteristics

(Note 2)

Parameter

Conditions

LM234-3

LM234-6

Units

Min

Typ

Max

Min

Typ

Max

Set Current Error, V

=2.5V,

100µA

SET

1mA

(Note 3)

= 25°

Equivalent Temperature Error

°C

Ratio of Set Current to

100µA

SET

1mA

Bias Current

Minimum Operating Voltage

100µA I

SET

1mA

0.9

Average Change in Set Current

100µA

SET

1mA

with Input Voltage

1.5

0.02

0.05

0.02

0.01

%/V

30V

0.01

0.03

0.01

0.05

%/V

Temperature Dependence of

100µA

SET

1mA

0.98T

1.02T

0.97T

1.03T

Set Current (Note 4) and

Equivalent Slope Error

Effective Shunt Capacitance

LM134/LM234/LM334

www.national.com

Typical Performance Characteristics

(Continued)

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.

CALCULATING R

SET

The total current through the LM134 (I

SET

) is the sum of the

current going through the SET resistor (I

) and the LM134's

bias current (I

BIAS

), as shown in

Figure 1.

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

determined by V

, which is approximately 214µV/°K (64

mV/298°K

214µV/°K).

Since (for a given set current) I

BIAS

is simply a percentage of

SET

, the equation can be rewritten

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

SET

1mA, the equation can

be 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

SET

. At

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

0.4°C in still air. Output current

SET

) 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
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.

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

Turn-On Voltage

DS005697-29

Ratio of I

SET

to I

BIAS

DS005697-3

DS005697-27

FIGURE 1. Basic Current Source

LM134/LM234/LM334

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ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: LM234H-6