LM2907EP/LM2917EP
Enhanced Plastic Frequency to Voltage Converter
General Description
The LM2907EP, LP2917EP series are monolithic frequency
to voltage converters with a high gain op amp/comparator
designed to operate a relay, lamp, or other load when the
input frequency reaches or exceeds a selected rate. The
tachometer uses a charge pump technique and offers fre-
quency doubling for low ripple, full input protection in two
versions (LM2907-8EP, LM2917-8EP) and its output swings
to ground for a zero frequency input.
The op amp/comparator is fully compatible with the tachom-
eter and has a floating transistor as its output. This feature
allows either a ground or supply referred load of up to 50 mA.
The collector may be taken above V
CC
up to a maximum V
CE
of 28V.
The two basic configurations offered include an 8-pin device
with a ground referenced tachometer input 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 conversion applications.
The more versatile configurations provide differential ta-
chometer input and uncommitted op amp inputs. With this
version the tachometer input may be floated and the op amp
becomes suitable for active filter conditioning of the tachom-
eter output.
Both of these configurations are available with an active
shunt regulator connected across the power leads. The
regulator clamps the supply such that stable frequency to
voltage and frequency to current operations are possible
with any supply voltage and a suitable resistor.
ENHANCED PLASTIC
•Extended Temperature Performance of −40˚C to +85˚C
•Baseline Control - Single Fab & Assembly Site
•Process Change Notification (PCN)
•Qualification & Reliability Data
•Solder (PbSn) Lead Finish is standard
•Enhanced Diminishing Manufacturing Sources (DMS)
Support
Features
nGround referenced tachometer input interfaces directly
with variable reluctance magnetic pickups
nOp amp/comparator has floating transistor output
n50 mA sink or source to operate relays, solenoids,
meters, or LEDs
nFrequency doubling for low ripple
nTachometer has built-in hysteresis with either differential
input or ground referenced input
nBuilt-in zener on LM2917EP
n±0.3% linearity typical
nGround referenced tachometer is fully protected from
damage due to swings above V
CC
and below ground
Advantages
nOutput swings to ground for zero frequency input
nEasy to use; V
OUT
=f
IN
xV
CC
xR1xC1
nOnly one RC network provides frequency doubling
nZener regulator on chip allows accurate and stable
frequency to voltage or current conversion (LM2917EP)
Applications
nSelected Military Applications
nSelected Avionics Applications
Ordering Information
PART NUMBER VIN PART NUMBER NS PACKAGE NUMBER (Note 3)
LM2907MX-8EP V62/04635-01 M08A
LM2917MXEP V62/04635-02 M14A
(Notes 1, 2) TBD TBD
Note 1: For the following (Enhanced Plastic) versions, check for availablility: LM2907M-8EP, LM2907MEP, LM2907MXEP, LM2907N-8EP, LM2907NEP
and LM2917M-8EP, LM2917MX-8EP, LM2917MEP, LM2917N-8EP, LM2917NEP. Parts listed with an "X" are provided in Tape & Reel and parts without
an "X" are in Rails.
Note 2: FOR ADDITIONAL ORDERING AND PRODUCT INFORMATION, PLEASE VISIT THE ENHANCED PLASTIC WEB SITE AT: www.national.com/
mil
Note 3: Refer to package details under Physical Dimensions
June 2004
LM2907EP/LM2917EP Enhanced Plastic Frequency to Voltage Converter
© 2004 National Semiconductor Corporation DS200906 www.national.com
Block and Connection Diagrams Dual-In-Line and Small Outline Packages, Top Views
20090601
LM2907-8
See NS Package Number M08A or N08E 20090602
LM2917-8
See NS Package Number M08A or N08E
20090603
LM2907
See NS Package Number M14A or N14A
20090604
LM2917
See NS Package Number M14A or N14A
LM2907EP/LM2917EP Enhanced Plastic
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Absolute Maximum Ratings (Note 4)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage 28V
Collector Voltage 28V
Differential Input Voltage
Tachometer 28V
Op Amp/Comparator 28V
Input Voltage Range
Tachometer
LM2907-8EP, LM2917-8EP ±28V
LM2907EP, LM2917EP 0.0V to +28V
Op Amp/Comparator 0.0V to +28V
Power Dissipation (Note 4)
LM2907-8EP, LM2917-8EP 1200 mW
LM2907-14EP, LM2917-14EP 1580 mW
Operating Temperature Range −40˚C to +85˚C
Storage Temperature Range −65˚C to +150˚C
Soldering Information
Dual-In-Line Package
Soldering (10 seconds) 260˚C
Small Outline Package
Vapor Phase (60 seconds) 215˚C
Infrared (15 seconds) 220˚C
Electrical Characteristics V
CC
=12V
DC
,T
A
= 25˚C, see test circuit
Symbol Parameter Conditions Min Typ Max Units
TACHOMETER
Input Thresholds V
IN
= 250 mVp-p @1 kHz (Note 5) ±10 ±25 ±40 mV
Hysteresis V
IN
= 250 mVp-p @1 kHz (Note 5) 30 mV
Offset Voltage V
IN
= 250 mVp-p @1 kHz (Note 5)
LM2907EP/LM2917EP 3.5 10 mV
LM2907-8EP/LM2917-8EP 5 15 mV
Input Bias Current V
IN
=±50 mV
DC
0.1 1 µA
V
OH
Pin 2 V
IN
= +125 mV
DC
(Note 6) 8.3 V
V
OL
Pin 2 V
IN
= −125 mV
DC
(Note 6) 2.3 V
I
2
,I
3
Output Current V2 = V3 = 6.0V (Note 7) 140 180 240 µA
I
3
Leakage Current I2 = 0, V3 = 0 0.1 µA
K Gain Constant (Note 6) 0.9 1.0 1.1
Linearity f
IN
= 1 kHz, 5 kHz, 10 kHz (Note 8) −1.0 0.3 +1.0 %
OP/AMP COMPARATOR
V
OS
V
IN
= 6.0V 3 10 mV
I
BIAS
V
IN
= 6.0V 50 500 nA
Input Common-Mode Voltage 0 V
CC
−1.5V V
Voltage Gain 200 V/mV
Output Sink Current V
C
= 1.0 40 50 mA
Output Source Current V
E
=V
CC
−2.0 10 mA
Saturation Voltage I
SINK
= 5 mA 0.1 0.5 V
I
SINK
=20mA 1.0 V
I
SINK
= 50 mA 1.0 1.5 V
ZENER REGULATOR
Regulator Voltage R
DROP
= 470Ω7.56 V
Series Resistance 10.5 15 Ω
Temperature Stability +1 mV/˚C
Total Supply Current 3.8 6 mA
Note 4: For operation in ambient temperatures above 25˚C, the device must be derated based on a 150˚C maximum junction temperature and a thermal resistance
of 101˚C/W junction to ambient for LM2907-8EP and LM2917-8EP, and 79˚C/W junction to ambient for LM2907-14EP and LM2917-14EP.
Note 5: Hysteresis is the sum +VTH − (−VTH), offset voltage is their difference. See test circuit.
Note 6: VOH is equal to
3
⁄
4
xV
CC −1V
BE,V
OL is equal to
1
⁄
4
xV
CC −1V
BE therefore VOH −V
OL =V
CC/2. The difference, VOH −V
OL, and the mirror gain, I2/I3,
are the two factors that cause the tachometer gain constant to vary from 1.0.
Note 7: Be sure when choosing the time constant R1 x C1 that R1 is such that the maximum anticipated output voltage at pin 3 can be reached with I3x R1. The
maximum value for R1 is limited by the output resistance of pin 3 which is greater than 10 MΩtypically.
Note 8: Nonlinearity is defined as the deviation of VOUT (@pin 3) for fIN = 5 kHz from a straight line defined by the VOUT @1 kHz and VOUT @10 kHz. C1 = 1000 pF,
R1 = 68k and C2 = 0.22 mFd.
LM2907EP/LM2917EP Enhanced Plastic
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Test Circuit and Waveform
20090606
Tachometer Input Threshold Measurement
20090607
LM2907EP/LM2917EP Enhanced Plastic
www.national.com 4
Typical Performance Characteristics
Total Supply Current
Zener Voltage vs
Temperature
20090640 20090641
Normalized Tachometer
Output vs Temperature
Normalized Tachometer
Output vs Temperature
20090642 20090643
Tachometer Currents I
2
and I
3
vs Supply Voltage
Tachometer Currents I
2
and I
3
vs Temperature
20090644 20090645
LM2907EP/LM2917EP Enhanced Plastic
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Typical Performance Characteristics (Continued)
Tachometer Linearity
vs Temperature
Tachometer Linearity
vs Temperature
20090646 20090647
Tachometer Linearity vs R1
Tachometer Input Hysteresis
vs Temperature
20090648 20090649
Op Amp Output Transistor
Characteristics
Op Amp Output Transistor
Characteristics
20090650 20090651
LM2907EP/LM2917EP Enhanced Plastic
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Applications Information
The LM2907EP series of tachometer circuits is designed for
minimum external part count applications and maximum ver-
satility. In order to fully exploit its features and advantages
let’s examine its theory of operation. The first stage of op-
eration is a differential amplifier driving a positive feedback
flip-flop circuit. The input threshold voltage is the amount of
differential input voltage at which the output of this stage
changes state. Two options (LM2907-8EP, LM2917-8EP)
have one input internally grounded so that an input signal
must swing above and below ground and exceed the input
thresholds to produce an output. This is offered specifically
for magnetic variable reluctance pickups which typically pro-
vide a single-ended ac output. This single input is also fully
protected against voltage swings to ±28V, which are easily
attained with these types of pickups.
The differential input options (LM2907EP, LM2917EP) give
the user the option of setting his own input switching level
and still have the hysteresis around that level for excellent
noise rejection in any application. Of course in order to allow
the inputs to attain common-mode voltages above ground,
input protection is removed and neither input should be
taken outside the limits of the supply voltage being used. It is
very important that an input not go below ground without
some resistance in its lead to limit the current that will then
flow in the epi-substrate diode.
Following the input stage is the charge pump where the input
frequency is converted to a dc voltage. To do this requires
one timing capacitor, one output resistor, and an integrating
or filter capacitor. When the input stage changes state (due
to a suitable zero crossing or differential voltage on the input)
the timing capacitor is either charged or discharged linearly
between two voltages whose difference is V
CC
/2. Then in
one half cycle of the input frequency or a time equal to 1/2 f
IN
the change in charge on the timing capacitor is equal to
V
CC
/2 x C1. The average amount of current pumped into or
out of the capacitor then is:
The output circuit mirrors this current very accurately into the
load resistor R1, connected to ground, such that if the pulses
of current are integrated with a filter capacitor, then V
O
=i
c
x
R1, and the total conversion equation becomes:
V
O
=V
CC
xf
IN
xC1xR1xK
Where K is the gain constant — typically 1.0.
The size of C2 is dependent only on the amount of ripple
voltage allowable and the required response time.
CHOOSING R1 AND C1
There are some limitations on the choice of R1 and C1 which
should be considered for optimum performance. The timing
capacitor also provides internal compensation for the charge
pump and should be kept larger than 500 pF for very accu-
rate operation. Smaller values can cause an error current on
R1, especially at low temperatures. Several considerations
must be met when choosing R1. The output current at pin 3
is internally fixed and therefore V
O
/R1 must be less than or
equal to this value. If R1 is too large, it can become a
significant fraction of the output impedance at pin 3 which
degrades linearity. Also output ripple voltage must be con-
sidered and the size of C2 is affected by R1. An expression
that describes the ripple content on pin 3 for a single R1C2
combination is:
It appears R1 can be chosen independent of ripple, however
response time, or the time it takes V
OUT
to stabilize at a new
voltage increases as the size of C2 increases, so a compro-
mise between ripple, response time, and linearity must be
chosen carefully.
As a final consideration, the maximum attainable input fre-
quency is determined by V
CC
, C1 and I
2
:
USING ZENER REGULATED OPTIONS (LM2917EP)
For those applications where an output voltage or current
must be obtained independent of supply voltage variations,
the LM2917EP is offered. The most important consideration
in choosing a dropping resistor from the unregulated supply
to the device is that the tachometer and op amp circuitry
alone require about 3 mA at the voltage level provided by the
zener. At low supply voltages there must be some current
flowing in the resistor above the 3 mA circuit current to
operate the regulator. As an example, if the raw supply
varies from 9V to 16V, a resistance of 470Ωwill minimize the
zener voltage variation to 160 mV. If the resistance goes
under 400Ωor over 600Ωthe zener variation quickly rises
above 200 mV for the same input variation.
LM2907EP/LM2917EP Enhanced Plastic
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Typical Applications
Minimum Component Tachometer
20090608
20090609
LM2907EP/LM2917EP Enhanced Plastic
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Typical Applications (Continued)
Zener Regulated Frequency to Voltage Converter
20090610
Breaker Point Dwell Meter
20090611
LM2907EP/LM2917EP Enhanced Plastic
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Typical Applications (Continued)
Voltage Driven Meter Indicating Engine RPM
V
O
=6V@400 Hz or 6000 ERPM (8 Cylinder Engine)
20090612
Current Driven Meter Indicating Engine RPM
I
O
=10mA@300 Hz or 6000 ERPM (6 Cylinder Engine)
20090613
LM2907EP/LM2917EP Enhanced Plastic
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Typical Applications (Continued)
Capacitance Meter
V
OUT
= 1V–10V for C
X
= 0.01 to 0.1 mFd
(R = 111k)
20090614
Two-Wire Remote Speed Switch
20090615
LM2907EP/LM2917EP Enhanced Plastic
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Typical Applications (Continued)
100 Cycle Delay Switch
20090616
Variable Reluctance Magnetic Pickup Buffer Circuits
20090639
Precision two-shot output frequency
equals twice input frequency.
Pulse height = VZENER
20090617
LM2907EP/LM2917EP Enhanced Plastic
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Typical Applications (Continued)
Finger Touch or Contact Switch
20090618
20090619
Flashing LED Indicates Overspeed
20090620
Flashing begins when fIN ≥100 Hz.
Flash rate increases with input frequency
increase beyond trip point.
LM2907EP/LM2917EP Enhanced Plastic
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Typical Applications (Continued)
Frequency to Voltage Converter with 2 Pole Butterworth Filter to Reduce Ripple
20090621
Overspeed Latch
20090622
20090623
LM2907EP/LM2917EP Enhanced Plastic
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Typical Applications (Continued)
Some Frequency Switch Applications May Require Hysteresis in the
Comparator Function Which can be Implemented in Several Ways:
20090624
20090625
20090626
20090627
20090628
LM2907EP/LM2917EP Enhanced Plastic
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Typical Applications (Continued)
Changing the Output Voltage for an Input Frequency of Zero
20090629
20090630
Changing Tachometer Gain Curve or Clamping the Minimum Output Voltage
20090631
20090632
LM2907EP/LM2917EP Enhanced Plastic
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Anti-Skid Circuit Functions
“Select-Low” Circuit
20090633
20090634
VOUT is proportional to the lower of the two input wheel speeds.
“Select-High” Circuit
20090635
20090636
VOUT is proportional to the higher of the two input wheel speeds.
“Select-Average” Circuit
20090637
LM2907EP/LM2917EP Enhanced Plastic
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Equivalent Schematic Diagram
20090638
*This connection made on LM2907-8EP and LM2917-8EP only.
**This connection made on LM2917EP and LM2917-8EP only.
LM2907EP/LM2917EP Enhanced Plastic
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Physical Dimensions inches (millimeters) unless otherwise noted
8-Lead (0.150" Wide) Molded Small Outline Package, JEDEC
NS Package Number M08A
14-Lead Molded SO Package
NS Package Number M14A
LM2907EP/LM2917EP Enhanced Plastic
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Molded Dual-In-Line Package (N)
NS Package Number N08E
Molded Dual-In-Line Package (N)
NS Package Number N14A
LM2907EP/LM2917EP Enhanced Plastic
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Notes
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NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
BANNED SUBSTANCE COMPLIANCE
National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products
Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification
(CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2.
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LM2907EP/LM2917EP Enhanced Plastic Frequency to Voltage Converter
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
