LM185-1.2/LM285-1.2/LM385-1.2 Micropower Voltage Reference Diode

LM185-1.2/LM285-1.2/LM385-1.2

Micropower Voltage Reference Diode

General Description

The

LM185-1.2/LM285-1.2/LM385-1.2

are

micropower

2-terminal band-gap voltage regulator diodes. Operating

over a 10 µA to 20 mA current range, they feature exception-

ally low dynamic impedance and good temperature stability.

On-chip trimming is used to provide tight voltage tolerance.

Since the LM185-1.2 band-gap reference uses only transis-

tors and resistors, low noise and good long term stability re-

sult.

Careful design of the LM185-1.2 has made the device ex-

ceptionally tolerant of capacitive loading, making it easy to

use in almost any reference application. The wide dynamic

operating range allows its use with widely varying supplies

with excellent regulation.

The extremely low power drain of the LM185-1.2 makes it

useful for micropower circuitry. This voltage reference can be

used to make portable meters, regulators or general purpose

analog circuitry with battery life approaching shelf life.

Further, the wide operating current allows it to replace older

references with a tighter tolerance part.

The LM185-1.2 is rated for operation over a −55˚C to 125˚C

temperature range while the LM285-1.2 is rated −40˚C to

85˚C and the LM385-1.2 0˚C to 70˚C. The LM185-1.2/

LM285-1.2 are available in a hermetic TO-46 package and

the LM285-1.2/LM385-1.2 are also available in a low-cost

TO-92 molded package, as well as SO and SOT-23. The

LM185-1.2 is also available in a hermetic leadless chip car-

rier package.

Features

4 mV (

0.3%) max. initial tolerance (A grade)

Operating current of 10 µA to 20 mA

0.6

Ω

max dynamic impedance (A grade)

Low temperature coefficient

Low voltage reference — 1.235V

2.5V device and adjustable device also available

LM185-2.5 series and LM185 series, respectively

Connection Diagrams

T0-92

Plastic Package (Z)

DS005518-10

Bottom View

Order Number LM285Z-1.2,

LM285BXZ-1.2, LM285BYZ-1.2

LM385Z-1.2, LM385BZ-1.2

LM385BXZ-1.2 or LM385BYZ-1.2

See NS Package Number Z03A

SOT23

DS005518-33

Pin 3 is attached to the Die Attach Pad (DAP) and should be connected

to Pin 2 or left floating.

Order Number LM385M3-1.2

See NS Package Number MA03B

January 2000

LM185-1.2/LM285-1.2/LM385-1.2

Micropower

oltage

Reference

Diode

DS005518

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.

(Note 2)

Reverse Current

30 mA

Forward Current

10 mA

Operating Temperature Range (Note 3)

LM185-1.2

−55˚C to +125˚C

LM285-1.2

−40˚C to +85˚C

LM385-1.2

0˚C to 70˚C

Storage Temperature

−55˚C to +150˚C

Soldering Information

TO-92 package: 10 sec.

260˚C

TO-46 package:10 sec.

300˚C

SO and SOT Pkg.

Vapor phase (60 sec.)

215˚C

Infrared (15 sec.)

220˚C

See AN-450 “Surface Mounting Methods and Their Effect

on Product Reliability” for other methods of soldering

surface mount devices.

Electrical Characteristics

(Note 4)

LM185-1.2

LM185BX-1.2

LM385B-1.2

LM185BY-1.2

LM385BX-1.2

LM385-1.2

LM285-1.2

LM385BY-1.2

Units

Parameter

Conditions

Typ

LM285BX-1.2

(Limit)

LM285BY-1.2

Tested

Design

Tested

Design

Tested

Design

Limit

(Notes

5, 8)

(Note 6)

(Note 5)

(Note 6)

(Note 5)

(Note 6)

Reverse Breakdown

= 25˚C,

1.235

1.223

1.205

V(Min)

Voltage

10 µA

≤

20 mA

1.247

1.260

V(Max)

Minimum Operating

µA

Current

LM385M3-1.2

(Max)

Reverse Breakdown

10 µA

≤

1 mA

1.5

Voltage Change

(Max)

with Current

1 mA

≤

20 mA

(Max)

Reverse Dynamic

= 100 µA, f = 20 Hz

Ω

Impedance

Wideband Noise

= 100 µA,

µV

(rms)

10 Hz

≤

10 kHz

Long Term Stability

= 100 µA, T = 1000 Hr,

ppm

= 25˚C

0.1˚C

Average Temperature

= 100 µA

Coefficient (Note 7)

X Suffix

ppm/˚C

Y Suffix

ppm/˚C

All Others

150

ppm/˚C

(Max)

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is in-

tended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The

guaranteed specifications apply only for the test conditions listed.

Note 2: Refer to RETS185H-1.2 for military specifications.

Note 3: For elevated temperature operation, T

max is:

LM185

150˚C

LM285

125˚C

LM385

100˚C

Thermal Resistance

TO-92

TO-46

SO-8

SOT23

(junction to ambient)

180˚C/W (0.4" leads)

440˚C/W

165˚C/W

283˚C/W

170˚C/W (0.125" leads)

(junction to case)

N/A

80˚C/W

N/A

Note 4: Parameters identified with boldface type apply at temperature extremes. All other numbers apply at T

= T

= 25˚C.

LM185-1.2/LM285-1.2/LM385-1.2

www.national.com

Electrical Characteristics

(Note 4) (Continued)

Note 5: Guaranteed and 100% production tested.

Note 6: Guaranteed, but not 100% production tested. These limits are not used to calculate average outgoing quality levels.

Note 7: The average temperature coefficient is defined as the maximum deviation of reference voltage at all measured temperatures between the operating T

MAX

and T

MIN

, divided by T

MAX

− T

MIN

. The measured temperatures are −55˚C, −40˚C, 0˚C, 25˚C, 70˚C, 85˚C, 125˚C.

Note 8: A military RETS electrical specification is available on request.

Typical Performance Characteristics

Reverse Characteristics

DS005518-13

Reverse Characteristics

DS005518-14

Forward Characteristics

DS005518-15

Temperature Drift of 3

Representative Units

DS005518-16

Reverse Dynamic Impedance

DS005518-17

Reverse Dynamic Impedance

DS005518-18

Noise Voltage

DS005518-19

Filtered Output Noise

DS005518-20

Response Time

DS005518-21

LM185-1.2/LM285-1.2/LM385-1.2

www.national.com

Typical Applications

(Continued)

METER THERMOMETERS

0˚C−100˚C Thermometer

DS005518-28

Calibration

1. Short LM385-1.2, adjust R3 for I

OUT

= temp at 1 µA/˚K

2. Remove short, adjust R2 for correct reading in centigrade

†

at 1.3V

≅

500 µA

at 1.6V

≅

2.4 mA

Lower Power Thermometer

DS005518-29

*2N3638 or 2N2907 select for inverse H

≅

†

Select for operation at 1.3V

‡

≅

600 µA to 900 µA

0˚F−50˚F Thermometer

DS005518-30

Calibration

1. Short LM385-1.2, adjust R3 for I

OUT

= temp at 1.8 µA/˚K

2. Remove short, adjust R2 for correct reading in ˚F

Micropower Thermocouple Cold Junction

Compensator

DS005518-31

Adjustment Procedure

1. Adjust TC ADJ pot until voltage across R1 equals Kelvin temperature

multiplied by the thermocouple Seebeck coefficient.

2. Adjust zero ADJ pot until voltage across R2 equals the thermocouple

Seebeck coefficient multiplied by 273.2.

Thermocouple

Seebeck

Voltage

Type

Coefficient

(

Ω

)

(

Ω

)

Across R1

Across R2

(µV/˚C)

25˚C

(mV)

52.3

523 1.24k

15.60

14.32

42.8

432

12.77

11.78

40.8

412 953

Ω

12.17

11.17

6.4

63.4 150

Ω

1.908

1.766

Typical supply current 50 µA

LM185-1.2/LM285-1.2/LM385-1.2

www.national.com

Notes

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT

DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL

COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or

systems which, (a) are intended for surgical implant

into the body, or (b) support or sustain life, and

whose failure to perform when properly used in

accordance with instructions for use provided in the

labeling, can be reasonably expected to result in a

significant injury to the user.

2. A critical component is any component of a life

support device or system whose failure to perform

can be reasonably expected to cause the failure of

the life support device or system, or to affect its

safety or effectiveness.

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www.national.com

LM185-1.2/LM285-1.2/LM385-1.2

Micropower

oltage

Reference

Diode

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.