LM2907-N, LM2917-N
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LM2907/LM2917 Frequency to Voltage Converter
Check for Samples: LM2907-N, LM2917-N
1FEATURES DESCRIPTION
The LM2907, LM2917 series are monolithic
2• Ground Referenced Tachometer Input
frequency to voltage converters with a high gain opInterfaces Directly With Variable Reluctance
amp/comparator designed to operate a relay, lamp, orMagnetic Pickups
other load when the input frequency reaches or
• Op Amp/Comparator Has Floating Transistor exceeds a selected rate. The tachometer uses a
Output charge pump technique and offers frequency
doubling for low ripple, full input protection in two• 50 mA Sink or Source to Operate Relays,
versions (LM2907-8, LM2917-8) and its output swingsSolenoids, Meters, or LEDs
to ground for a zero frequency input.
• Frequency Doubling For Low Ripple
The op amp/comparator is fully compatible with the
• Tachometer Has Built-In Hysteresis With
tachometer and has a floating transistor as its output.Either Differential Input or Ground Referenced This feature allows either a ground or supply referredInput load of up to 50 mA. The collector may be taken
• Built-In Zener on LM2917 above VCC up to a maximum VCE of 28V.
• ±0.3% Linearity Typical The two basic configurations offered include an 8-pin
• Ground Referenced Tachometer is Fully device with a ground referenced tachometer input
Protected From Damage Due to Swings Above and an internal connection between the tachometer
output and the op amp non-inverting input. ThisVCC and Below Ground
version is well suited for single speed or frequency
switching or fully buffered frequency to voltageAPPLICATIONS
conversion applications.
• Over/Under Speed Sensing
The more versatile configurations provide differential
• Frequency to Voltage Conversion tachometer input and uncommitted op amp inputs.(Tachometer) With this version the tachometer input may be floated
• Speedometers and the op amp becomes suitable for active filter
conditioning of the tachometer output.• Breaker Point Dwell Meters
• Hand-Held Tachometer Both of these configurations are available with an
active shunt regulator connected across the power• Speed Governors
leads. The regulator clamps the supply such that
• Cruise Control stable frequency to voltage and frequency to current
• Automotive Door Lock Control operations are possible with any supply voltage and a
suitable resistor.• Clutch Control
• Horn Control
• Touch or Sound Switches
ADVANTAGES
• Output Swings to Ground For Zero Frequency
Input
• Easy to Use; VOUT = fIN × VCC × R1 × C1
• Only One RC Network provides Frequency
Doubling
• Zener Regulator on Chip allows Accurate and
Stable Frequency to Voltage or Current
Conversion (LM2917)
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 2000–2013, Texas Instruments IncorporatedProducts conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
LM2907-N, LM2917-N
SNAS555C –JUNE 2000–REVISED MARCH 2013 www.ti.com
CONNECTION DIAGRAMS
PDIP and SOIC Packages, Top Views
Figure 1. See Package Number D0008A or P0008E Figure 2. See Package Number D0008A or P0008E
Figure 3. See Package Number D0014A or Figure 4. See Package Number D0014A or
NFF0014A NFF0014A
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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
ABSOLUTE MAXIMUM RATINGS (1) (2)
Supply Voltage 28V
Supply Current (Zener Options) 25 mA
Collector Voltage 28V
Differential Input Voltage Tachometer 28V
Op Amp/Comparator 28V
Input Voltage Range Tachometer LM2907-8, LM2917-8 ±28V
LM2907, LM2917 0.0V to +28V
Op Amp/Comparator 0.0V to +28V
Power Dissipation LM2907-8, LM2917-8 1200 mW
LM2907-14, LM2917-14 (1) 1580 mW
Operating Temperature Range −40°C to +85°C
Storage Temperature Range −65°C to +150°C
Soldering Information PDIP Package Soldering (10 seconds) 260°C
SOIC Package Vapor Phase (60 seconds) 215°C
Infrared (15 seconds) 220°C
(1) 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 LM2907-8 and LM2917-8, and 79°C/W junction to ambient for LM2907-14 and
LM2917-14.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
ELECTRICAL CHARACTERISTICS
VCC = 12 VDC, TA = 25°C, see test circuit
Symbol Parameter Conditions Min Typ Max Units
TACHOMETER
Input Thresholds VIN = 250 mVp-p @ 1 kHz (1) ±10 ±25 ±40 mV
Hysteresis VIN = 250 mVp-p @ 1 kHz (1) 30 mV
Offset Voltage VIN = 250 mVp-p @ 1 kHz (1)
LM2907/LM2917 3.5 10 mV
LM2907-8/LM2917-8 5 15 mV
Input Bias Current VIN = ±50 mVDC 0.1 1 μA
VOH Pin 2 VIN = +125 mVDC(2) 8.3 V
VOL Pin 2 VIN = −125 mVDC(2) 2.3 V
I2, I3 Output Current V2 = V3 = 6.0V (3) 140 180 240 μA
I3 Leakage Current I2 = 0, V3 = 0 0.1 μA
K Gain Constant See (2) 0.9 1.0 1.1
Linearity fIN = 1 kHz, 5 kHz, 10 kHz (4) −1.0 0.3 +1.0 %
OP/AMP COMPARATOR
VOS VIN = 6.0V 3 10 mV
IBIAS VIN = 6.0V 50 500 nA
Input Common-Mode 0 VCC−1.5V V
Voltage
(1) Hysteresis is the sum +VTH − (−VTH), offset voltage is their difference. See test circuit.(2) VOH is equal to ¾ × VCC − 1 VBE, VOL is equal to ¼ × 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 1.0.(3) Be sure when choosing the time constant R1 × C1 that R1 is such that the maximum anticipated output voltage at pin 3 can be reached
with I3 × R1. The maximum value for R1 is limited by the output resistance of pin 3 which is greater than 10 MΩ typically.(4) 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.
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ELECTRICAL CHARACTERISTICS (continued)
VCC = 12 VDC, TA = 25°C, see test circuit
Symbol Parameter Conditions Min Typ Max Units
Voltage Gain 200 V/mV
Output Sink Current VC = 1.0 40 50 mA
Output Source Current VE = VCC −2.0 10 mA
Saturation Voltage ISINK = 5 mA 0.1 0.5 V
ISINK = 20 mA 1.0 V
ISINK = 50 mA 1.0 1.5 V
ZENER REGULATOR
Regulator Voltage RDROP = 470Ω 7.56 V
Series Resistance 10.5 15 Ω
Temperature Stability +1 mV/°C
Total Supply Current 3.8 6 mA
TEST CIRCUIT AND WAVEFORM
Figure 5.
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Tachometer Input Threshold Measurement
Figure 6.
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TYPICAL PERFORMANCE CHARACTERISTICS
Tachometer Linearity vs Temperature Tachometer Linearity vs Temperature
Figure 7. Figure 8.
Total Supply Current Zener Voltage vs Temperature
Figure 9. Figure 10.
Normalized Tachometer Output (K) vs Temperature Normalized Tachometer Output (K) vs Temperature
Figure 11. Figure 12.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Tachometer Currents I2and I3 vs Supply Voltage Tachometer Currents I2and I3 vs Temperature
Figure 13. Figure 14.
Tachometer Linearity vs R1 Tachometer Input Hysteresis vs Temperature
Figure 15. Figure 16.
Op Amp Output Transistor Characteristics Op Amp Output Transistor Characteristics
Figure 17. Figure 18.
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APPLICATIONS INFORMATION
The LM2907 series of tachometer circuits is designed for minimum external part count applications and
maximum versatility. In order to fully exploit its features and advantages let's 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
(LM2907-8, LM2917-8) 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 ±28V, 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 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 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 then is:
(1)
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 equation
becomes:
VO = VCC × fIN × C1 × R1 × K
where
• K is the gain constant—typically 1.0 (2)
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 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:
(3)
It appears 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 I2:
(4)
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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 9V to 16V, a
resistance of 470Ω will minimize the zener voltage variation to 160 mV. If the resistance goes under 400Ω or
over 600Ω the zener variation quickly rises above 200 mV for the same input variation.
TYPICAL APPLICATIONS
Figure 19. Minimum Component Tachometer
Figure 20. ”Speed Switch”, Load is Energized when fIN ≥ (1 / ( 2RC))
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Figure 21. Zener Regulated Frequency to Voltage Converter
Figure 22. Breaker Point Dwell Meter
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Figure 23. Voltage Driven Meter Indicating Engine RPM
VO = 6V @ 400 Hz or 6000 ERPM (8 Cylinder Engine)
Figure 24. Current Driven Meter Indicating Engine RPM
IO = 10 mA @ 300 Hz or 6000 ERPM (6 Cylinder Engine)
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Figure 25. Capacitance Meter
VOUT = 1V–10V for CX = 0.01 to 0.1 mFd (R = 111k)
Figure 26. Two-Wire Remote Speed Switch
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Figure 27. 100 Cycle Delay Switch
Variable Reluctance Magnetic Pickup Buffer Circuits
Precision two-shot output frequency
equals twice input frequency.
Pulse height = VZENER
Figure 28. Figure 29.
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Finger Touch or Contact Switch
Figure 30. Figure 31.
Flashing begins when fIN ≥ 100 Hz.
Flash rate increases with input frequency
increase beyond trip point.
Figure 32. Flashing LED Indicates Overspeed
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Figure 33. Frequency to Voltage Converter with 2 Pole Butterworth Filter to Reduce Ripple
Figure 34. Overspeed Latch
Figure 36.
Figure 35.
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Frequency Switch Applications
Some frequency switch applications may require hysteresis in the comparator function which can be
implemented in several ways.
Figure 37.
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Figure 38. Figure 39.
Figure 40. Figure 41.
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Changing the Output Voltage for an Input Frequency of Zero
Figure 42. Figure 43.
Changing Tachometer Gain Curve or Clamping the Minimum Output Voltage
Figure 44. Figure 45.
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ANTI-SKID CIRCUIT FUNCTIONS
“Select-Low” Circuit
VOUT Proportional to the Lower
of the Two Input Wheel Speeds
Figure 46. Figure 47.
“Select-High” Circuit
VOUT Proportional to the Higher
of the Two Input Wheel Speeds
Figure 48. Figure 49.
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“Select-Average” Circuit
Figure 50.
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EQUIVALENT SCHEMATIC DIAGRAM
*This connection made on LM2907-8 and LM2917-8 only.
**This connection made on LM2917 and LM2917-8 only.
Figure 51.
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REVISION HISTORY
Changes from Revision B (March 2013) to Revision C Page
• Changed layout of National Data Sheet to TI format .......................................................................................................... 21
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PACKAGE OPTION ADDENDUM
www.ti.com 9-Aug-2013
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing
Pins Package
Qty
Eco Plan
(2)
Lead/Ball Finish MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LM2907M ACTIVE SOIC D 14 55 TBD Call TI Call TI -40 to 85 LM2907M
LM2907M-8 ACTIVE SOIC D 8 95 TBD Call TI Call TI -40 to 85 LM29
07M-8
LM2907M-8/NOPB ACTIVE SOIC D 8 95 Green (RoHS
& no Sb/Br)
CU SN Level-1-260C-UNLIM -40 to 85 LM29
07M-8
LM2907M/NOPB ACTIVE SOIC D 14 55 Green (RoHS
& no Sb/Br)
CU SN Level-1-260C-UNLIM -40 to 85 LM2907M
LM2907MX ACTIVE SOIC D 14 2500 TBD Call TI Call TI -40 to 85 LM2907M
LM2907MX-8 ACTIVE SOIC D 8 2500 TBD Call TI Call TI -40 to 85 LM29
07M-8
LM2907MX-8/NOPB ACTIVE SOIC D 8 2500 Green (RoHS
& no Sb/Br)
CU SN Level-1-260C-UNLIM -40 to 85 LM29
07M-8
LM2907MX/NOPB ACTIVE SOIC D 14 2500 Green (RoHS
& no Sb/Br)
CU SN Level-1-260C-UNLIM -40 to 85 LM2907M
LM2907N ACTIVE PDIP NFF 14 25 TBD Call TI Call TI -40 to 85 LM2907N
LM2907N-8 ACTIVE PDIP P 8 40 TBD Call TI Call TI -40 to 85 LM
2907N-8
LM2907N-8/NOPB ACTIVE PDIP P 8 40 Green (RoHS
& no Sb/Br)
CU SN Level-1-NA-UNLIM -40 to 85 LM
2907N-8
LM2907N/NOPB ACTIVE PDIP NFF 14 25 Green (RoHS
& no Sb/Br)
CU SN Level-1-NA-UNLIM -40 to 85 LM2907N
LM2917M ACTIVE SOIC D 14 55 TBD Call TI Call TI -40 to 85 LM2917M
LM2917M-8 ACTIVE SOIC D 8 95 TB
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