LM2907 LM2917 Frequency to Voltage Converter
February 1995
LM2907 LM2917 Frequency to Voltage Converter
General Description
The LM2907 LM2917 series are monolithic frequency to
voltage converters with a high gain op amp comparator de-
signed to operate a relay lamp or other load when the input
frequency reaches or exceeds a selected rate The tachom-
eter uses a charge pump technique and offers frequency
doubling for low ripple full input protection in two versions
(LM2907-8 LM2917-8) and its output swings to ground for a
zero frequency input
Y
Y
Y
Y
Y
Frequency doubling for low ripple
Tachometer has built-in hysteresis with either differen-
tial input or ground referenced input
Built-in zener on LM2917
g
0 3% linearity typical
Ground referenced tachometer is fully protected from
damage due to swings above V
CC
and below ground
Applications
Y
Y
Y
Y
Y
Y
Y
Y
Advantages
Y
Y
Y
Y
Output swings to ground for zero frequency input
Easy to use V
OUT
e
f
IN
c
V
CC
c
R1
c
C1
Only one RC network provides frequency doubling
Zener regulator on chip allows accurate and stable fre-
quency to voltage or current conversion (LM2917)
Features
Y
Y
Y
Y
Y
Y
Ground referenced tachometer input interfaces directly
with variable reluctance magnetic pickups
Op amp comparator has floating transistor output
50 mA sink or source to operate relays solenoids me-
ters or LEDs
Over under speed sensing
Frequency to voltage conversion (tachometer)
Speedometers
Breaker point dwell meters
Hand-held tachometer
Speed governors
Cruise control
Automotive door lock control
Clutch control
Horn control
Touch or sound switches
Block and Connection Diagrams
Dual-In-Line and Small Outline Packages
Top Views
TL H 7942 – 1
TL H 7942 – 2
Order Number LM2907M-8 or LM2907N-8
See NS Package Number M08A or N08E
Order Number LM2917M-8 or LM2917N-8
See NS Package Number M08A or N08E
TL H 7942 – 3
TL H 7942 – 4
Order Number LM2907N
See NS Package Number N14A
C
1995 National Semiconductor Corporation
TL H 7942
Order Number LM2917M or LM2917N
See NS Package Number M14A or N14A
RRD-B30M115 Printed in U S A
NSC [ NATIONAL SEMICONDUCTOR ]
