LM231A/LM231/LM331A/LM331

Precision Voltage-to-Frequency Converters

General Description

The LM231/LM331 family of voltage-to-frequency converters

are ideally suited for use in simple low-cost circuits for

analog-to-digital conversion, precision frequency-to-voltage

conversion, long-term integration, linear frequency modula-

tion or demodulation, and many other functions. The output

when used as a voltage-to-frequency converter is a pulse

train at a frequency precisely proportional to the applied

input voltage. Thus, it provides all the inherent advantages of

the voltage-to-frequency conversion techniques, and is easy

to apply in all standard voltage-to-frequency converter appli-

cations. Further, the LM231A/LM331A attain a new high

level of accuracy versus temperature which could only be

attained with expensive voltage-to-frequency modules. Ad-

ditionally the LM231/331 are ideally suited for use in digital

systems at low power supply voltages and can provide low-

cost

analog-to-digital

conversion

in

microprocessor-

controlled systems. And, the frequency from a battery pow-

ered voltage-to-frequency converter can be easily channeled

through a simple photo isolator to provide isolation against

high common mode levels.

The LM231/LM331 utilize a new temperature-compensated

band-gap reference circuit, to provide excellent accuracy

over the full operating temperature range, at power supplies

as low as 4.0V. The precision timer circuit has low bias

currents without degrading the quick response necessary for

100 kHz voltage-to-frequency conversion. And the output

are capable of driving 3 TTL loads, or a high voltage output

up to 40V, yet is short-circuit-proof against V

CC.

Features

n

Guaranteed linearity 0.01% max

n

Improved performance in existing voltage-to-frequency

conversion applications

n

Split or single supply operation

n

Operates on single 5V supply

n

Pulse output compatible with all logic forms

n

Excellent temperature stability: ±50 ppm/˚C max

n

Low power consumption: 15 mW typical at 5V

n

Wide dynamic range, 100 dB min at 10 kHz full scale

frequency

n

Wide range of full scale frequency: 1 Hz to 100 kHz

n

Low cost

Connection Diagram

Dual-In-Line Package

00568021

Order Number LM231AN, LM231N, LM331AN,

or LM331N

See NS Package Number N08E

Ordering Information

Device

Temperature Range

Package

LM231N

−25˚C

≤ T

A

≤ +85˚C

N08E (DIP)

LM231AN

−25˚C

≤ T

A

≤ +85˚C

N08E (DIP)

LM331N

0˚C

≤ T

A

≤ +70˚C

N08E (DIP)

LM331AN

0˚C

≤ T

A

≤ +70˚C

N08E (DIP)

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April 2006