LM2907-N, LM2917-N

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SNAS555C – JUNE 2000 – REVISED MARCH 2013

LM2907/LM2917 Frequency to Voltage Converter

Check for Samples: LM2907-N, LM2917-N

1

FEATURES

DESCRIPTION

The

LM2907,

LM2917

series

are

monolithic

2

•

Ground Referenced Tachometer Input

frequency to voltage converters with a high gain op

Interfaces Directly With Variable Reluctance

amp/comparator designed to operate a relay, lamp, or

Magnetic Pickups

other load when the input frequency reaches or

•

Op Amp/Comparator Has Floating Transistor

exceeds a selected rate. The tachometer uses a

Output

charge

pump

technique

and

offers

frequency

doubling for low ripple, full input protection in two

•

50 mA Sink or Source to Operate Relays,

versions (LM2907-8, LM2917-8) and its output swings

Solenoids, Meters, or LEDs

to ground for a zero frequency input.

•

Frequency Doubling For Low Ripple

The op amp/comparator is fully compatible with the

•

Tachometer Has Built-In Hysteresis With

tachometer and has a floating transistor as its output.

Either Differential Input or Ground Referenced

This feature allows either a ground or supply referred

Input

load of up to 50 mA. The collector may be taken

•

Built-In Zener on LM2917

•

±0.3% Linearity Typical

The two basic configurations offered include an 8-pin

•

Ground Referenced Tachometer is Fully

device with a ground referenced tachometer input

Protected From Damage Due to Swings Above

and an internal connection between the tachometer

output and the op amp non-inverting input. This

version is well suited for single speed or frequency

switching or fully buffered frequency to voltage

APPLICATIONS

conversion applications.

•

Over/Under Speed Sensing

The more versatile configurations provide differential

•

Frequency to Voltage Conversion

tachometer input and uncommitted op amp inputs.

(Tachometer)

With this version the tachometer input may be floated

•

Speedometers

and the op amp becomes suitable for active filter

conditioning of the tachometer output.

•

Breaker Point Dwell Meters

•

Hand-Held Tachometer

Both of these configurations are available with an

active shunt regulator connected across the power

•

Speed Governors

leads. The regulator clamps the supply such that

•

Cruise Control

stable frequency to voltage and frequency to current

•

Automotive Door Lock Control

operations are possible with any supply voltage and a

suitable resistor.

•

Clutch Control

•

Horn Control

•

Touch or Sound Switches

ADVANTAGES

•

Output Swings to Ground For Zero Frequency

Input

•

•

Only One RC Network provides Frequency

Doubling

•

Zener Regulator on Chip allows Accurate and

Stable Frequency to Voltage or Current

Conversion (LM2917)

1

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2

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PRODUCTION DATA information is current as of publication date.

Copyright © 2000–2013, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.