LM2907, LM2917 FREQUENCY-TO-VOLTAGE CONVERTERS SLFS011A – MARCH 1986 – REVISED JULY 1993 D D D D D D D Output Swings to Ground for Zero-Frequency Input Only One RC Network Provides Frequency Doubling for Low Ripple 8-Pin Versions Interface Directly to Variable-Reluctance Magnetic Pickups Uncommitted Collector and Emitter Outputs Provide 40-mA Sink or Source Current to Operate Relays, Solenoids, Meters, or LEDs Built-In Hysteresis for Noise Immunity Linearity Typically ± 0.3% 8-Pin Versions Are Fully Protected From Damage Due to TACH Input Swing Above VCC and Below Ground LM2907, LM2917 . . . D OR P PACKAGE (TOP VIEW) TACH + CAP1 CPO/IN + E 1 8 2 7 3 6 4 5 GND IN – VCC C LM2907, LM2917 . . . D OR N PACKAGE (TOP VIEW) TACH + CAP1 CPO IN + E NC NC 1 14 2 13 3 12 4 11 5 10 6 9 7 8 NC NC GND TACH – IN – VCC C applications NC – No internal connection Over/under speed sensing Frequency-to-voltage conversion Speedometers Breaker-point dwell meters Hand-held tachometers Speed governors Cruise controls Automotive door-lock controls Clutch controls Horn controls Touch or sound switches AVAILABLE OPTIONS PACKAGED DEVICES TA – 40°C to 85°C SMALL OUTLINE (D) PLASTIC DIP (N) PLASTIC DIP (P) L2907D8 — LM2907P L2907D14 LM2907N — L2917D8 — LM2917P L2917D14 LM2917N — description The LM2907 and LM2917 are monolithic frequency-to-voltage converters. Each device has an output circuit that activates loads such as relays and lamps when the input frequency reaches or exceeds a selected rate. The converter (tachometer) section consists of a comparator driving a charge pump and offers frequency doubling for low ripple, full input protection in 8-pin versions, and an output swing to ground for a zero-frequency input. The output section consists of an operational amplifier, normally operating as a comparator, that drives an output transistor with both the collector and emitter floating. The circuit can either sink or source 40 mA of load current. Two basic configurations are offered: 8-pin devices and 14-pin devices. Each 8-pin version has a groundreferenced tachometer input and an internal connection between the tachometer output and the operational amplifier input. The 8-pin versions are suited to single-speed or single-frequency switching or fully buffered frequency-to-voltage conversion applications. The more versatile 14-pin versions provide differential tachometer inputs and uncommitted operational amplifier inputs. The tachometer input can be floated, and the operational amplifier becomes suitable for active filter conditioning of the tachometer output. The LM2917 has an active shunt regulator connected across the power leads. The regulator clamps the supply voltage so that stable frequency-to-voltage and frequency-to-current conversions are possible with any supply voltage and a suitable resistor. The LM2907 and LM2917 are designed for operation from – 40°C to 85°C. Copyright 1993, Texas Instruments Incorporated PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 LM2907, LM2917 FREQUENCY-TO-VOLTAGE CONVERTERS SLFS011A – MARCH 1986 – REVISED JULY 1993 functional block diagrams IN – 7 TACH + 1 VCC 6 5 C IN – 4 TACH + 1 E TACH – 11 – + Charge Pump 3 CAP1 CPO/IN + VCC 10 8 C 5 E – + Charge Pump 3 CAP1 CPO 4 IN + 9 (LM2917 only) (LM2917 only) 14-PIN VERSIONS 8-PIN VERSIONS absolute maximum ratings over operating free-air temperature range (unless otherwise noted)† Supply voltage, VCC: LM2907 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 V Supply current, ICC: LM2917 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 mA Collector-to-emitter voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 V Operational amplifier input voltage range, IN + and IN – . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V to VCC Tachometer input voltage range: 8-pin version TACH+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V to 28 V 14-pin version TACH+ and TACH– . . . . . . . . . . . . . . . . . . . . . . . . 0 V to VCC Continuous total dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Dissipation Rating Table Operating free-air temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 40°C to 85°C Storage temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 65°C to 150°C Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C † Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the recommended operating conditions section of this specification is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. DISSIPATION RATING TABLE 2 PACKAGE TA ≤ 25°C POWER RATING DERATING FACTOR ABOVE TA = 25°C TA = 85°C POWER RATING D (8 pin) 725 mW 5.8 mW/°C 377 mW D (14 pin) 950 mW 7.6 mW/°C 494 mW N 1150 mW 9.2 mW/°C 598 mW P 1000 mW 8.0 mW/°C 520 mW POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 LM2907, LM2917 FREQUENCY-TO-VOLTAGE CONVERTERS SLFS011A – MARCH 1986 – REVISED JULY 1993 electrical characteristics, VCC = 12 V (LM2907), V+† = 12 V through 470 Ω (LM2917), TA = 25°C converter (tachometer) section PARAMETER VIT Vhys TEST CONDITIONS Input threshold voltage Input hysteresis (see Note 1) 8-pin versions LM2907 MIN LM2917 TYP MAX ± 15 ± 40 ± 8.5 MIN ± 8.5 TYP ± 15 MAX ± 40 VI = 250 mV, VI = 250 mV, f = 1 kHz f = 1 kHz 30 VI = 250 mV, VID = 250 mV, f = 1 kHz 5 15 5 15 f = 1 kHz 3.5 10 3.5 10 VI = ± 50 mV 0.1 1 0.1 1 30 UNIT mV mV VIO Input offset voltage g (see Note 1) IIB Input bias current VOH High-level output voltage CAP1 VI or VID = 125 mV 8.3 5 V VOL Low-level output voltage CAP1 VI or VID = – 125 mV 2.3 1.2 V IO Output current CAP1 CPO CAP1, Leakage current CPO 14-pin versions CAP1 and CPO at 6 V 200 240 CAP1 and CPO at 3.8 V 140 CAP1 open, CPO at 0 V, See Note 3 200 0.1 Gain constant Nonlinearity (see Note 2) 140 0.9 f = 1 kHz, 5 kHz, or 10 kHz 1 1.1 0.3 ±1 240 0.1 0.9 1 1.1 0.3 ±1 mV µA µA µA % output section PARAMETER TEST CONDITIONS VIO Input offset voltage VI = 6 V, VI = 3.8 V, IIB Input bias current VI = 6 V VI = 3.8 V AV IC Voltage amplification IE Emitter output (source) current VCE(sat) ( ) Collector output (sink) current Collector-emitter saturation voltage LM2907 MIN TYP See Note 3 3 LM2917 MAX MIN 40 IC = 20 mA IC = 50 mA 50 40 – 10 0.1 3 10 50 500 500 200 VC = 1 V, VE = 0 VC = VCC, VE = VCC – 2 IC = 5 mA MAX 10 See Note 3 50 TYP 1 mV nA 200 V/mV 50 mA – 10 0.5 UNIT 0.1 mA 0.5 1 V 1 1.5 1 1.5 † V+ is the symbol for voltage applied to a series resistor to create a current source. NOTES: 1. Hysteresis is the algebraic difference VIT+ – VIT– ; offset voltage is the difference in magnitudes |VIT +| – |VIT – |. See parameter measurement information test circuit. 2. Nonlinearity is defined as the deviation of VO at CPO for f = 5 kHz from a straight line defined by the VO at 1 kHz and VO at 10 kHz, with C1 = 1000 pF, R1 = 68 Ω, C2 = 0.22 µF. 3. CAP1 must be bypassed with a 0.001-µF capacitor to prevent oscillation for these tests. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3 LM2907, LM2917 FREQUENCY-TO-VOLTAGE CONVERTERS SLFS011A – MARCH 1986 – REVISED JULY 1993 zener regulator (LM2917 only), V +† = 12 V through 470 Ω, TA = 25°C PARAMETER VZ αVZ MIN Regulated supply voltage TYP MAX 7.56 Temperature coefficient of regulated supply voltage V 1 rs Series resistance † V+ is the symbol for voltage applied to a series resistor to create a current source. UNIT mV/°C 10.5 15 TYP MAX 3.8 6 Ω total device (LM2907 only), VCC = 12 V, TA = 25°C PARAMETER ICC MIN Supply current PARAMETER MEASUREMENT INFORMATION TACH + Charge Pump CAP1 CPO C1 R1 TEST CIRCUIT ≈ 15 mV ≈ – 15 mV TACH + VCC 2 VOH CAP1 VOL I × R1 (I ≈ 200 µA) CPO WAVEFORMS Figure 1. Test Circuit and Waveforms 4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 UNIT mA LM2907, LM2917 FREQUENCY-TO-VOLTAGE CONVERTERS SLFS011A – MARCH 1986 – REVISED JULY 1993 APPLICATION INFORMATION The LM2907 and LM2917 frequency-to-voltage converter circuits provide maximum versatility with a minimum of external parts. The first stage of each device is a differential comparator. The single-input 8-pin versions have one input grounded so that an input signal must swing above and below GND and exceed the input thresholds to produce an output. This version is specifically for magnetic variable-reluctance pickups, which typically provide a single-ended ac output. These single-ended inputs are fully protected against voltage swings to ± 28 V, which are easily attained by this type of pickup. The differential-input 14-pin versions provide the option of setting the input reference level, maintaining hysteresis around that level to provide excellent noise rejection in any application. The input protection is removed in the 14-pin versions. Therefore, neither of the differential inputs should exceed the limits of the supply voltage. An input must not go below GND without a resistance in the lead to limit the current that flows in the episubstrate diode. The charge-pump circuit that follows the input state produces a dc output voltage proportional to the input frequency. The charge-pump circuit (see Figures 1 and 2) consists of a timing capacitor (C1), an output resistor (R1), and an integrating or filter capacitor (C2). When the input changes state (due to a suitable zero crossing or differential voltage on the input), the timing capacitor is either charged or discharged linearly with a constant current of 200 µA through CAP1 between two voltages whose difference is VCC /2. Within one-half cycle of the input frequency or a time equal to 1/2f, the change in charge on C1 is equal to (VCC /2)C1. The average amount of current pumped into or out of the capacitor is: CAP1 current (average) + QT + C1 • V2CC • 2f + VCC • f • C1 The output of the charge pump accurately mirrors the CAP1 current into the load resistor (R1) connected to CPO. If the pulses of current are integrated with a filter capacitor, the output voltage is the average CAP1 current times R1 and the total equation becomes: VO + VCC • f • C1 • R1 • K where K is the gain factor, which is typically one. The size of C2 is dependent only on the amount of ripple allowable and the required response time. selection of R1, C1, and C2 To achieve optimum performance, there are some limitations to be considered in the selection of R1 and C1. The timing capacitor controls the RC time and provides internal compensation for the charge-pump circuit. For very accurate operation, it should be 100 pF or greater. Smaller values, especially at lower temperatures, can cause an error current through R1. VO/R1 must be less than or equal to the output current at CPO, which is fixed typically at 200 µA. If R1 is too large, it becomes a significant fraction of the output impedance at CPO, which degrades the linearity. In addition, ripple voltage must be considered when selecting R1. The size of C2 is directly affected by the size of R1. An expression that describes the ripple content at CPO is: V ripple • C1 • (1 * V CC • f • C1 + VCC 2 200 C2 ) volts peak-to-peak where: C1 and C2 are in farads, VCC is in volts, and f is in hertz. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5 LM2907, LM2917 FREQUENCY-TO-VOLTAGE CONVERTERS SLFS011A – MARCH 1986 – REVISED JULY 1993 APPLICATION INFORMATION R1 cannot be chosen independent of ripple because response time or the time it takes VO to stabilize at a new level increases as the size of C2 increases. 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 Icap (current through CAP1). f max + C1 I•capV hertz CC where: Icap is typically 200 µA, C1 is in farads, and VCC is in volts. zener regulator options (LM2917) For those applications in which an output voltage or current must be obtained independent of supply voltage variations, the LM2917 can be used. The most important factor in selecting a dropping resistor for the unregulated supply is that the frequency-to-voltage converter circuit and the operational amplifier alone require approximately 3 mA at the voltage level set by the zener diode. 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 supply voltage varies between 9 V and 16 V, a resistance of 470 Ω minimizes the zener voltage variation to typically 160 mV. If the resistance goes under 400 Ω or above 600 Ω, the zener variation quickly rises above 200 mV for the same input variation. VCC TACH + Charge Pump + – CAP1 CAPO/IN + C1 E IN – R1 C2 10 kΩ Figure 2. Minimum-Component Tachometer 6 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 Emitter/Follower Output IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. 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