LM2907, LM2917
FREQUENCY-TO-VOLTAGE CONVERTERS
SLFS011A – MARCH 1986 – REVISED JULY 1993
D
D
D
D
D
D
D
Output Swings to Ground for
Zero-Frequency Input
Only One RC Network Provides Frequency
Doubling for Low Ripple
8-Pin Versions Interface Directly to
Variable-Reluctance Magnetic Pickups
Uncommitted Collector and Emitter
Outputs Provide 40-mA Sink or Source
Current to Operate Relays, Solenoids,
Meters, or LEDs
Built-In Hysteresis for Noise Immunity
Linearity Typically
±
0.3%
8-Pin Versions Are Fully Protected From
Damage Due to TACH Input Swing Above
V
CC
and Below Ground
LM2907, LM2917 . . . D OR P PACKAGE
(TOP VIEW)
TACH +
CAP1
CPO/IN +
E
1
2
3
4
8
7
6
5
GND
IN –
V
CC
C
LM2907, LM2917 . . . D OR N PACKAGE
(TOP VIEW)
TACH +
CAP1
CPO
IN +
E
NC
NC
1
2
3
4
5
6
7
14
13
12
11
10
9
8
NC
NC
GND
TACH –
IN –
V
CC
C
applications
NC – No internal connection
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
AVAILABLE OPTIONS
PACKAGED DEVICES
TA
SMALL
OUTLINE
(D)
L2907D8
– 40°C to 85°C
L2907D14
L2917D8
L2917D14
PLASTIC
DIP
(N)
—
LM2907N
—
LM2917N
PLASTIC
DIP
(P)
LM2907P
—
LM2917P
—
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.
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.
Copyright
©
1993, Texas Instruments Incorporated
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
1
TI [ TEXAS INSTRUMENTS ]
