LM2907, LM2917

FREQUENCY-TO-VOLTAGE CONVERTERS

SLFS011A – MARCH 1986 – REVISED JULY 1993

1

POST OFFICE BOX 655303

Zero-Frequency Input

Doubling for Low Ripple

Variable-Reluctance Magnetic Pickups

Outputs Provide 40-mA Sink or Source

Current to Operate Relays, Solenoids,

Meters, or LEDs

Damage Due to TACH Input Swing Above

applications

Over/under speed sensing

Frequency-to-voltage conversion

Speedometers

Breaker-point dwell meters

Hand-held tachometers

Speed governors

Cruise controls

Automotive door-lock controls

Clutch controls

Horn controls

Touch or sound switches

description

The LM2907 and LM2917 are monolithic frequency-to-voltage converters. Each device has an output circuit

that activates loads such as relays and lamps when the input frequency reaches or exceeds a selected rate.

The converter (tachometer) section consists of a comparator driving a charge pump and offers frequency

doubling for low ripple, full input protection in 8-pin versions, and an output swing to ground for a zero-frequency

input. The output section consists of an operational amplifier, normally operating as a comparator, that drives

an output transistor with both the collector and emitter floating. The circuit can either sink or source 40 mA of

load current.

Two basic configurations are offered: 8-pin devices and 14-pin devices. Each 8-pin version has a ground-

referenced tachometer input and an internal connection between the tachometer output and the operational

amplifier input. The 8-pin versions are suited to single-speed or single-frequency switching or fully buffered

frequency-to-voltage conversion applications. The more versatile 14-pin versions provide differential

tachometer inputs and uncommitted operational amplifier inputs. The tachometer input can be floated, and the

operational amplifier becomes suitable for active filter conditioning of the tachometer output.

The LM2917 has an active shunt regulator connected across the power leads. The regulator clamps the supply

voltage so that stable frequency-to-voltage and frequency-to-current conversions are possible with any supply

voltage and a suitable resistor.

The LM2907 and LM2917 are designed for operation from – 40

°C to 85°C.

Copyright

© 1993, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

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2

3

4

8

7

6

5

TACH +

CAP1

CPO/IN +

E

GND

IN –

C

LM2907, LM2917 ...D OR P PACKAGE

1

2

3

4

5

6

7

14

13

12

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9

8

TACH +

CAP1

CPO

IN +

E

NC

NC

NC

NC

GND

TACH –

IN –

C

LM2907, LM2917 ...D OR N PACKAGE

NC – No internal connection

AVAILABLE OPTIONS

–40

°C to 85°C

PACKAGED DEVICES

SMALL

OUTLINE

(D)

PLASTIC

DIP

(N)

PLASTIC

DIP

(P)

L2907D8

L2907D14

L2917D8

L2917D14

—

LM2907N

—

LM2917N

LM2907P

—

LM2917P

—

TA

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