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An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM2907-N
,
LM2917-N
SNAS555D –JUNE 2000–REVISED DECEMBER 2016
LM2907 and LM2917 Frequency to Voltage Converter
1
1 Features
1• Ground Referenced Tachometer Input Interfaces
Directly With Variable Reluctance Magnetic
Pickups
• Op Amp Has Floating Transistor Output
• 50-mA Sink or Source to Operate Relays,
Solenoids, Meters, or LEDs
• Frequency Doubling For Low Ripple
• Tachometer Has Built-In Hysteresis With Either
Differential Input or Ground Referenced Input
• ±0.3% Linearity (Typical)
• Ground-Referenced Tachometer is Fully Protected
From Damage Due to Swings Above VCC and
Below Ground
• Output Swings to Ground For Zero Frequency
Input
• Easy to Use; VOUT = fIN × VCC × R1 × C1
• Zener Regulator on Chip allows Accurate and
Stable Frequency to Voltage or Current
Conversion (LM2917)
2 Applications
• Over- and Under-Speed Sensing
• Frequency-to-Voltage Conversion (Tachometer)
• Speedometers
• Breaker Point Dwell Meters
• Hand-Held Tachometers
• Speed Governors
• Cruise Control
• Automotive Door Lock Control
• Clutch Control
• Horn Control
• Touch or Sound Switches
3 Description
The LM2907 and LM2917 devices are monolithic
frequency-to-voltage converters with a high gain op
amp 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 frequency doubling for low-
ripple, full-input protection in two versions (8-pin
LM2907 and LM2917), and its output swings to
ground for a zero frequency input.
The op amp is fully compatible with the tachometer
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 VCC up to a
maximum VCE of 28 V.
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 noninverting input. This
version is well suited for single speed or frequency
switching or fully buffered frequency-to-voltage
conversion applications.
Device Information(1)
PART NUMBER PACKAGE BODY SIZE (NOM)
LM2907-N,
LM2917-N
PDIP (8) 6.35 mm × 9.81 mm
PDIP (14) 6.35 mm × 19.177 mm
SOIC (8) 3.91 mm × 4.90 mm
SOIC (14) 3.91 mm × 8.65 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Minimum Component Tachometer Diagram
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Table of Contents
1 Features.................................................................. 1
2 Applications ........................................................... 1
3 Description............................................................. 1
4 Revision History..................................................... 2
5 Description (continued)......................................... 3
6 Pin Configuration and Functions......................... 3
7 Specifications......................................................... 5
7.1 Absolute Maximum Ratings ...................................... 5
7.2 ESD Ratings.............................................................. 5
7.3 Recommended Operating Conditions....................... 5
7.4 Thermal Information.................................................. 6
7.5 Electrical Characteristics........................................... 6
7.6 Typical Characteristics.............................................. 7
8 Parameter Measurement Information .................. 9
9 Detailed Description............................................ 10
9.1 Overview................................................................. 10
9.2 Functional Block Diagram....................................... 11
9.3 Feature Description................................................. 11
9.4 Device Functional Modes........................................ 12
10 Application and Implementation........................ 13
10.1 Application Information.......................................... 13
10.2 Typical Applications .............................................. 14
11 Power Supply Recommendations ..................... 27
12 Layout................................................................... 28
12.1 Layout Guidelines ................................................. 28
12.2 Layout Example .................................................... 28
13 Device and Documentation Support................. 29
13.1 Related Links ........................................................ 29
13.2 Receiving Notification of Documentation Updates 29
13.3 Community Resources.......................................... 29
13.4 Trademarks........................................................... 29
13.5 Electrostatic Discharge Caution............................ 29
13.6 Glossary................................................................ 29
14 Mechanical, Packaging, and Orderable
Information........................................................... 29
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (March 2013) to Revision D Page
• Added Device Information table, Pin Configuration and Functions section, ESD Ratings table, Recommended
Operating Conditions table, Thermal Information table, Parameter Measurement Information section, Detailed
Description section, Application and Implementation section, Power Supply Recommendations section, Layout
section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section...... 1
• Deleted Built-In Zener on LM2917 from Features.................................................................................................................. 1
• Deleted Only One RC Network Provides Frequency Doubling from Features....................................................................... 1
• Added Thermal Information table........................................................................................................................................... 6
• Changed tablenote text From: C2 = 0.22 mFd To: C2 = 0.22 µF.......................................................................................... 6
Changes from Revision B (March 2013) to Revision C Page
• Changed layout of National Semiconductor Data Sheet to TI format .................................................................................... 1
1TACH+ 8 TACH±/GND
2CP1 7 IN±
3CP2/IN+ 6 V+
4EMIT 5 COL
Not to scale
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5 Description (continued)
The more versatile configurations provide differential tachometer 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
tachometer 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.
6 Pin Configuration and Functions
P and D Package
8-Pin PDIP and SOIC
Top View
Pin Functions: 8 Pins
PIN I/O DESCRIPTION
NAME NO.
COL 5 I The collector of the bipolar junction transistor
CP1 2 O A capacitor placed on this pin will be charged up to VCC/2 by a constant current source of 180 µA
typical at the start of every positive half cycle. At the beginning of negative half cycles this capacitor
is discharged the same amount at the same rate.
CP2/IN+ 3 I/O See pins CP1 and IN+. On 8-pin devices (8-pin LM2907 and LM2917) these two nodes share a pin
and are internally connected.
EMIT 4 O The emitter of the bipolar junction transistor
GND — G Ground
IN+ — I The noninverting input to the high gain op amp
IN– 7 I The inverting input to the high gain op amp
NC — — No connect
TACH+ 1 I Positive terminal for the input signal that leads to the noninverting terminal of the internal Schmitt-
Trigger comparator.
TACH–/GND 8 I Negative terminal for the input signal that leads to the noninverting terminal of the internal Schmitt-
Trigger comparator. (NOTE: On 8-pin devices, LM2907 and LM2917, this pin is internally connected
to ground and must be tied to ground externally to provide the reference voltage of the device).
V+ 6 I Supply voltage
1TACH+ 14 NC
2CP1 13 NC
3CP2 12 GND
4IN+ 11 TACH±
5EMIT 10 IN±
6NC 9 V+
7NC 8 COL
Not to scale
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NFF and D Package
14-Pin PDIP and SOIC
Top View
Pin Functions: 14 Pins
PIN I/O DESCRIPTION
NAME NO.
COL 8 I The collector of the bipolar junction transistor
CP1 2 O A capacitor placed on this pin will be charged up to VCC/2 by a constant current source of 180 µA
typical at the start of every positive half cycle. At the beginning of negative half cycles this capacitor is
discharged the same amount at the same rate.
CP2 3 O The charge pump sources current out of this pin equal to the absolute value of the capacitor current
on CP1. A resistor and capacitor in parallel connected to this pin filters the current pulses into the
output voltage.
EMIT 5 O The emitter of the bipolar junction transistor
GND 12 G Ground
IN+ 4 I The noninverting input to the high gain op amp
IN– 10 I The inverting input to the high gain op amp
NC 6, 7, 13, 14 — No connect
TACH+ 1 I Positive terminal for the input signal that leads to the noninverting terminal of the internal Schmitt-
Trigger comparator.
TACH– 11 I Negative terminal for the input signal that leads to the noninverting terminal of the internal Schmitt-
Trigger comparator.
V+ 9 I Supply voltage
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(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)(1)(2)
MIN MAX UNIT
Supply voltage 28 V
Supply current (Zener options) 25 mA
Collector voltage 28 V
Differential input voltage Tachometer, op amp, and comparator 28 V
Input voltage Tachometer LM2907 (8), LM2917 (8) –28 28 VLM2907 (14), LM2917 (14) 0 28
Op amp and comparator 0 28
Power dissipation LM29x7 (8) 1200 mW
LM29x7 (14) 1580
Soldering information PDIP package Soldering (10 s) 260 °C
SOIC package Vapor phase (60 s) 215
Infrared (15 s) 220
Operating temperature, TJ–40 85 °C
Storage temperature, Tstg –65 150 °C
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
7.2 ESD Ratings VALUE UNIT
V(ESD) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JESD22-A114(1) ±1000 V
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) ±250
7.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) MIN NOM MAX UNIT
Input voltage LM2907 (8), LM2917 (8) –28 28 V
LM2907 (14), LM2917 (14) 0 28 V
Output sink current 50 mA
6
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(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
7.4 Thermal Information
THERMAL METRIC(1) LM2907, LM2917
UNITP (PDIP) D (SOIC) NFF (PDIP) D (SOIC)
8 PINS 8 PINS 14 PINS 14 PINS
RθJA Junction-to-ambient thermal resistance 77.6 110 69.1 83.7 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 80.5 53.9 64.8 42.1 °C/W
RθJB Junction-to-board thermal resistance 54.8 50.4 49.1 38 °C/W
ψJT Junction-to-top characterization parameter 37.6 9.1 35.1 7.7 °C/W
ψJB Junction-to-board characterization
parameter 54.8 49.9 49 37.7 °C/W
RθJC(bot) Junction-to-case (bottom) thermal
resistance — — — — °C/W
(1) Hysteresis is the sum VTH – (–VTH), offset voltage is their difference. See test circuit.
(2) VOH = 0.75 × VCC – 1 VBE and VOL = 0.25 × VCC – 1 VBE, therefore VOH – VOL = VCC / 2. The difference (VOH – VOL) and the mirror gain
(I2/ I3) are the two factors that cause the tachometer gain constant to vary from 1.
(3) Ensure that when choosing the time constant R1 × C1 that the maximum anticipated output voltage at CP2/IN+ can be reached with I3×
R1. The maximum value for R1 is limited by the output resistance of CP2/IN+ which is greater than 10 MΩtypically.
(4) Nonlinearity is defined as the deviation of VOUT (at CP2/IN+) for fIN = 5 kHz from a straight line defined by the VOUT at 1 kHz and VOUT
at 10 kHz. C1 = 1000 pF, R1 = 68 kΩand C2 = 0.22 µF.
7.5 Electrical Characteristics
VCC = 12 VDC, TA= 25°C, see test circuit
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
TACHOMETER
Input thresholds VIN = 250 mVp-p at 1 kHz(1) ±10 ±25 ±40 mV
Hysteresis VIN = 250 mVp-p at 1 kHz(1) 30 mV
LM29x7 offset voltage VIN = 250 mVp-p at 1 kHz(1) 3.5 10 mV
VIN = 250 mVp-p at 1 kHz (8-pin LM29x7)(1) 5 15
Input bias current VIN = ±50 mVDC 0.1 1 μA
VOH High level output voltage For CP1, VIN = 125 mVDC(2) 8.3 V
VOL Low level output voltage For CP1, VIN = –125 mVDC(2) 2.3 V
I2, I3Output current V2 = V3 = 6 V(3) 140 180 240 μA
I3Leakage current I2 = 0, V3 = 0 0.1 μA
K Gain constant See(2) 0.9 1 1.1
Linearity fIN = 1 kHz, 5 kHz, or 10 kHz(4) –1% 0.3% 1%
OP AMP AND COMPARATOR
VOS Input offset voltage VIN = 6 V 3 10 mV
IBIAS Bias current VIN = 6 V 50 500 nA
Input common-mode voltage 0 VCC–1.5 V
Voltage gain 200 V/mV
Output sink current VC= 1 40 50 mA
Output source current VE= VCC –2 10 mA
Saturation voltage
ISINK = 5 mA 0.1 0.5 V
ISINK = 20 mA 1 V
ISINK = 50 mA 1 1.5 V
ZENER REGULATOR
Regulator voltage RDROP = 470 Ω7.56 V
Series resistance 10.5 15 Ω
Temperature stability 1 mV/°C
Total supply current 3.8 6 mA
7
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7.6 Typical Characteristics
Figure 1. Tachometer Linearity vs Temperature Figure 2. Tachometer Linearity vs Temperature
Figure 3. Total Supply Current Figure 4. Zener Voltage vs Temperature
Figure 5. Normalized Tachometer Output (K)
vs Temperature Figure 6. Normalized Tachometer Output (K)
vs Temperature
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Typical Characteristics (continued)
Figure 7. Tachometer Currents I2and I3vs Supply Voltage Figure 8. Tachometer Currents I2and I3vs Temperature
Figure 9. Tachometer Linearity vs R1 Figure 10. Tachometer Input Hysteresis vs Temperature
Figure 11. Op Amp Output Transistor Characteristics Figure 12. Op Amp Output Transistor Characteristics
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9 Detailed Description
9.1 Overview
The LM29x7 frequency-to-voltage converter features two separate inputs to monitor the signal. In the 8-pin
devices, one of these inputs is internally grounded and therefore it monitors the remaining input for zero
crossings. In the 14-pin devices, both of these inputs are open and it instead detects whenever the differential
voltage switches polarity. Therefore, the input comparator outputs a square wave of equal frequency to the input.
A charge pump system is used to translate the frequency of this square wave to a voltage. At the start of every
positive half cycle of the input signal a 180-µA constant current charges C1 until its voltage has increased by
VCC/2. The capacitor is held at that voltage until the input signal begins a negative half cycle. Then the 180-µA
constant current discharges capacitor C1 until its voltage has dropped by VCC/2. This voltage is held until the
next positive half cycle and the process repeats. This generates pulses of current flowing into and out of
capacitor C1 at the same frequency as the input signal. For every full cycle, the charge pump mirrors both
current pulses as positive current pulses into the parallel combination of resistor R1 and capacitor C2. Therefore
every full cycle, the amount of charge leaving pin 3 is equal to the sum of the charge entering C1 and leaving C1.
Because the voltage at pin 3 is equal to I3(avg) × R1, I(avg) is calculated in Equation 1.
I3(avg) = Q/t = (Qcharge + Qdischarge) / (1 / f) = 2 × Q × f = 2 × C1 × (VCC/2) × f = C1 × VCC × f (1)
This average current will be flowing across R1, giving the output voltage in Equation 2.
Vo = R1 × C1 × VCC × f (2)
C2 acts as a filter to smooth the pulses of current and does not affect the output voltage. However, the size of C2
determines both the output response time for changes in frequency and the amount of output voltage ripple.
The voltage generated is then fed in a high gain op amp. This op amp drives a bipolar transistor whose collector
and emitter are each broken out to a pin. The LM29x7 has the flexibility to be configured a variety of ways to
meet system requirements including voltage output, driving loads, operating a relay, and more.
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9.2 Functional Block Diagram
*This connection made on 8-pin LM2907 and LM2917 only.
**This connection made on LM2917 and 8-pin LM2917 only.
9.3 Feature Description
9.3.1 Differential Input
This device features a Schmitt-Trigger comparator that is the first stage in converting the input signal. Every time
the output of the comparator flips between high and low correlates to a half cycle elapsing on the input signal. On
the LM29x7-8 devices, one terminal of this comparator is internally connected to ground. This requires that the
input signal cross zero volts in order for device to detect the frequency. On the LM29x7 devices, the input
terminals to the Schmitt-Trigger comparator are both available for use. This open terminal allows the potential at
which the comparator’s output is flipped to be applied externally. This allows the device to accept signals with DC
offset or compare differential inputs.
9.3.2 Configurable
While the ratio of output voltage to input frequency is dependent on supply voltage, it is easily adjusted through
the combination of one resistor and one capacitor, R1 and C1. The formula for calculating the expected output
voltage is in Equation 3.
VOUT = VCC × f × C1 × R1. (3)
The sizes of R1 and C1 have other effects on the system such as maximum frequency and output linearity. See
Choosing R1 and C1 for detailed instructions on sizing components.
12
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Feature Description (continued)
9.3.3 Output Stage
The output voltage generated by the charge pump is fed in the noninverting terminal of a high gain op amp. This
op amp then drives and uncommitted bipolar junction transistor. This allows the LM2907 to be configured a
variety of ways to meet system needs. The output voltage can be buffered and used to drive a load (see
Figure 15) or an output threshold can be given to trigger a load switch (see Figure 18).
9.4 Device Functional Modes
9.4.1 Grounded Input Devices (8-Pin LM2907 and LM2917)
These devices have one of the two Schmitt-Trigger comparator inputs internally grounded and must be externally
connected to the system ground as well. This configuration monitors the remaining terminal for zero crossings.
9.4.2 Differential Input Devices (LM2907 and LM2917)
These devices have both inputs to the Schmitt-Trigger comparator available and broken out to pins 1 and 11.
This configuration allows a new switching threshold provided in the case of signals with DC offset or to intake a
differential pair and switch based on voltage difference.
CC
c(AVG) IN CC IN
V
Q= i =C1× ×(2f ) = V ×f ×C1
T 2
'
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10 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
10.1 Application Information
The LM2907 series of tachometer circuits is designed for minimum external part count applications and
maximum versatility. To fully exploit its features and advantages, first examine its theory of operation. The first
stage of operation 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 (8-pin
LM2907 and LM2917) 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 provide a single-ended AC output. This single input is also fully protected
against voltage swings to ±28 V, which are easily attained with these types of pickups.
The differential input options (LM2907, LM2917) 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 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 VCC/2. Then in one half cycle of the
input frequency or a time equal to 1/2 fIN the change in charge on the timing capacitor is equal to VCC/2 × C1.
The average amount of current pumped into or out of the capacitor is shown in Equation 4.
(4)
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 VO= ic× R1, and the total conversion formula
becomes Equation 5.
VO= VCC × fIN × C1 × R1 × K
where
• K is the gain constant (typically 1) (5)
The size of C2 is dependent only on the amount of ripple voltage allowable and the required response time.
CC CC IN
RIPPLE 2
V V ×f ×C1
C1
V = × × 1 pk-pk
2 C2 I
§ ·
¨ ¸
© ¹
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10.2 Typical Applications
10.2.1 Minimum Component Tachometer
Figure 15. Minimum Component Tachometer Diagram
10.2.1.1 Design Requirements
• C1: This capacitor is charged and discharged every cycle by a 180-µA typical current source. Smaller
capacitors can be charged quicker therefore increasing the maximum readable frequency. However, lower
capacitors values reduce the output voltage produced for a given frequency. C1 must not be sized lower than
500-pF die to its role in internal compensation.
• R1: This resistor produces the output voltage from current pulses source by the internal charge pump. Higher
values increase the output voltage for a given frequency, but too large will degrade the output’s linearity.
Because the current pulses are a fixed magnitude of 180 µA typical, R1 must be big enough to produce the
maximum desired output voltage at maximum input frequency. At maximum input frequency the pulse train
duty cycle is 100%, therefore the average current is 180 µA and R1 = Vo(max) / 180 µA.
• C2: This capacitor filters the ripple produced by the current pulses sourced by the charge pump. Large values
reduce the output voltage ripple but increase the output’s response time to changes in input frequency.
• Rload: The load resistance must be large enough that at maximum output voltage, the current is under the
rated value of 50 mA.
10.2.1.2 Detailed Design Procedure
10.2.1.2.1 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 must be kept larger than 500
pF for very accurate 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 VO/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 considered 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 in Equation 6.
(6)
R1 can be chosen independent of ripple. However, response time, or the time it takes VOUT to stabilize at a new
voltage, increases as the size of C2 increases, so a compromise between ripple, response time, and linearity
must be chosen carefully.
As a final consideration, the maximum attainable input frequency is determined by VCC, C1, and I2in Equation 7.
2
MAX CC
I
f = C1×V
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Typical Applications (continued)
(7)
10.2.1.2.2 Using Zener Regulated Options (LM2917)
For those applications where an output voltage or current must be obtained independent of supply voltage
variations, the LM2917 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 9 V to 16 V,
a resistance of 470 Ωminimizes the Zener voltage variation to 160 mV. If the resistance goes under 400 Ωor
over 600 Ω, the Zener variation quickly rises above 200 mV for the same input variation.
10.2.1.3 Application Curves
C1 = .01 µF C2 = 1 µF R1 = 100 kΩ
Rdrop = 910 ΩZener Regulated VCC = 7.58 V
Figure 16. Output Response to an Increase
in Input Frequency
C1 = .01 µF C2 = 1 µF R1 = 100 kΩ
Rdrop = 910 ΩZener Regulated VCC = 7.58 V
Figure 17. Output Voltage Ripple
10.2.2 Other Application Circuits
This section shows application circuit examples using the LM2907-N and LM2917-N devices. Customers must
fully validate and test these circuits before implementing a design based on these examples.
SPACER
Load is energized when fIN ≥(1 / ( 2 × RC))
Figure 18. Speed Switch
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SNAS555D –JUNE 2000–REVISED DECEMBER 2016
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Typical Applications (continued)
Figure 19. Zener Regulated Frequency to Voltage Converter
SPACER
Figure 20. Breaker Point Dwell Meter
SPACER
17
LM2907-N
,
LM2917-N
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SNAS555D –JUNE 2000–REVISED DECEMBER 2016
Product Folder Links: LM2907-N LM2917-N
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Typical Applications (continued)
VO= 6 V at 400 Hz or 6000 ERPM (8 Cylinder Engine)
Figure 21. Voltage Driven Meter Indicating Engine RPM
SPACER
IO= 10 mA at 300 Hz or 6000 ERPM (6 Cylinder Engine)
Figure 22. Current Driven Meter Indicating Engine RPM
SPACER
18
LM2907-N
,
LM2917-N
SNAS555D –JUNE 2000–REVISED DECEMBER 2016
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Product Folder Links: LM2907-N LM2917-N
Submit Documentation Feedback Copyright © 2000–2016, Texas Instruments Incorporated
Typical Applications (continued)
VOUT = 1 V to 10 V for CX = 0.01 to 0.1 mFd and R = 111 kΩ
Figure 23. Capacitance Meter
SPACER
Figure 24. Two-Wire Remote Speed Switch
SPACER
19
LM2907-N
,
LM2917-N
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SNAS555D –JUNE 2000–REVISED DECEMBER 2016
Product Folder Links: LM2907-N LM2917-N
Submit Documentation FeedbackCopyright © 2000–2016, Texas Instruments Incorporated
Typical Applications (continued)
V3 steps up in voltage by the amount of (VCC × C1) / C2, for each complete input cycle (2 zero crossings).
For example: if C2 = 200 × C1 after 100 consecutive input cycles, then V3 = 1/2 × VCC.
Figure 25. 100 Cycle Delay Switch
SPACER
Flashing begins when fIN ≥100 Hz
Flash rate increases with input frequency increase beyond trip point.
Figure 26. Flashing LED Indicates Over-Speed
SPACER