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  • LM2907 and LM2917 Frequency to Voltage Converter

    • SNAS555D June   2000  – December 2016 LM2907-N , LM2917-N

      PRODUCTION DATA.  

  • CONTENTS
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  • LM2907 and LM2917 Frequency to Voltage Converter
  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Differential Input
      2. 9.3.2 Configurable
      3. 9.3.3 Output Stage
    4. 9.4 Device Functional Modes
      1. 9.4.1 Grounded Input Devices (8-Pin LM2907 and LM2917)
      2. 9.4.2 Differential Input Devices (LM2907 and LM2917)
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 Minimum Component Tachometer
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1 Choosing R1 and C1
          2. 10.2.1.2.2 Using Zener Regulated Options (LM2917)
        3. 10.2.1.3 Application Curves
      2. 10.2.2 Other Application Circuits
        1. 10.2.2.1 Variable Reluctance Magnetic Pickup Buffer Circuits
        2. 10.2.2.2 Finger Touch or Contact Switch
        3. 10.2.2.3 Over-Speed Latch
        4. 10.2.2.4 Frequency Switch Applications
          1. 10.2.2.4.1 Application Curves
        5. 10.2.2.5 Anti-Skid Circuits
          1. 10.2.2.5.1 Select-Low Circuit
          2. 10.2.2.5.2 Select-High Circuit
          3. 10.2.2.5.3 Select-Average Circuit
        6. 10.2.2.6 Changing the Output Voltage for an Input Frequency of Zero
        7. 10.2.2.7 Changing Tachometer Gain Curve or Clamping the Minimum Output Voltage
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Related Links
    2. 13.2 Receiving Notification of Documentation Updates
    3. 13.3 Community Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information
  15. IMPORTANT NOTICE

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メカニカル・データ（パッケージ｜ピン）
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  • N|14
    • MPDI002C
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    • MPDS177H
  • P|8
    • MPDI001B
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DATA SHEET

LM2907 and LM2917 Frequency to Voltage Converter

1 Features

  • 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

LM2907-N LM2917-N key_graphic_SNAS555.png

4 Revision History

Changes from C Revision (March 2013) to D Revision

  • 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 sectionGo
  • Deleted Built-In Zener on LM2917 from FeaturesGo
  • Deleted Only One RC Network Provides Frequency Doubling from FeaturesGo
  • Added Thermal Information tableGo
  • Changed tablenote text From: C2 = 0.22 mFd To: C2 = 0.22 µFGo

Changes from B Revision (March 2013) to C Revision

  • Changed layout of National Semiconductor Data Sheet to TI formatGo

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
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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