LM1949N

LM1949 www.ti.com SNLS349C – FEB 1995 – REVISED MARCH 2013 LM1949 Injector Drive Controller Check for Samples: LM1949 FEATURES DESCRIPTION • • • • • • • • • • • • • APPLICATIONS The LM1949 linear integrated circuit serves as an excellent control of fuel injector drive circuitry in modern automotive systems. The IC is designed to control an external power NPN Darlington transistor that drives the high current injector solenoid. The current required to open a solenoid is several times greater than the current necessary to merely hold it open; therefore, the LM1949, by directly sensing the actual solenoid current, initially saturates the driver until the “peak” injector current is four times that of the idle or “holding” current (Figure 19–Figure 22). This guarantees opening of the injector. The current is then automatically reduced to the sufficient holding level for the duration of the input pulse. In this way, the total power consumed by the system is dramatically reduced. Also, a higher degree of correlation of fuel to the input voltage pulse (or duty cycle) is achieved, since opening and closing delays of the solenoid will be reduced. • • • • • Normally powered from a 5V ± 10% supply, the IC is typically operable over the entire temperature range (−55°C to +125°C ambient) with supplies as low as 3 volts. This is particularly useful under “cold crank” conditions when the battery voltage may drop low enough to deregulate the 5-volt power supply. 1 2 Low Voltage Supply (3V–5.5V) 22 mA Output Drive Current No RFI Radiation Adaptable to All Injector Current Levels Highly Accurate Operation TTL/CMOS Compatible Input Logic Levels Short Circuit Protection High Impedance Input Externally Set Holding Current, IH Internally Set Peak Current (4 × IH) Externally Set Time-Out Can be Modified for Full Switching Operation Available in Plastic 8-Pin PDIP Fuel Injection Throttle Body Injection Solenoid Controls Air and Fluid Valves DC Motor Drives The LM1949 is available in the plastic PDIP, (contact factory for other package options). Typical Application Figure 1. Typical Application and Test Circuit 1 2 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. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 1995–2013, Texas Instruments Incorporated LM1949 SNLS349C – FEB 1995 – REVISED MARCH 2013 www.ti.com 1 OUT 2 COMP 3 SENSE INPUT 4 LM1949N IN 8 TIMER 7 SUPPLY 6 SUPPLY GND 5 SENSE GND Figure 2. Package Number P0008E 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 8V (3) 1235 mW Input Voltage Range −0.3V to VCC Power Dissipation Operating Temperature Range −40°C to +125°C Storage Temperature Range −65°C to +150°C Junction Temperature 150°C Lead Temp. (Soldering 10 sec.) 260°C (1) (2) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. 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 100°C/W junction to ambient. (3) Electrical Characteristics (VCC = 5.5V, VIN = 2.4V, TJ = 25°C, Figure 1, unless otherwise specified.) Symbol ICC VOH VOL Parameter Conditions Units VIN = 0V 11 23 mA Pin 8 = 0V 28 54 mA Hold Pin 8 Open 16 26 mA VCC = 5.5V 1.4 2.4 V VCC = 3.0V 1.2 1.6 V Input On Level Input Off Level Input Current Output Current VCC = 5.5V 1.0 1.35 V VCC = 3.0V 0.7 1.15 V −25 3 −22 Peak Pin 8 = 0V −10 Hold Pin 8 Open −1.5 VS Output Saturation Voltage 10 mA, VIN = 0V VP Sense Input Peak Threshold 2 Max Peak IOP t Typ Off IB VH Min Supply Current VCC = 4.75V Hold Reference Time-out, t t ÷ RTCT Submit Documentation Feedback +25 µA mA −5 mA 0.2 0.4 V 350 386 415 mV 88 94 102 mV 90 100 110 % Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 LM1949 www.ti.com SNLS349C – FEB 1995 – REVISED MARCH 2013 Typical Performance Characteristics Output Current vs Supply Voltage Supply Current vs Supply Voltage Figure 3. Figure 4. Quiescent Current vs Supply Voltage Input Voltage Thresholds vs Supply Voltage Figure 5. Figure 6. Sense Input Peak Voltage vs Supply Voltage Sense Input Hold Voltage vs Supply Voltage Figure 7. Figure 8. Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 3 LM1949 SNLS349C – FEB 1995 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) 4 Normalized Timer Function vs Supply Voltage Quiescent Supply Current vs Junction Temperature Figure 9. Figure 10. Quiescent Supply Current vs Junction Temperature Output Current vs Junction Temperature Figure 11. Figure 12. Input Voltage Thresholds vs Junction Temperature Sense Input Peak Voltage vs Junction Temperature Figure 13. Figure 14. Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 LM1949 www.ti.com SNLS349C – FEB 1995 – REVISED MARCH 2013 Typical Performance Characteristics (continued) Sense Input Hold Voltage vs Junction Temperature Normalized Timer Function vs Junction Temperature Figure 15. Figure 16. LM1949N Junction Temperature Rise Above Ambient vs Supply Voltage Figure 17. Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 5 LM1949 SNLS349C – FEB 1995 – REVISED MARCH 2013 www.ti.com Typical Circuit Waveforms Figure 18. APPLICATION HINTS The injector driver integrated circuits were designed to be used in conjunction with an external controller. The LM1949 derives its input signal from either a control oriented processor (COPS™), microprocessor, or some other system. This input signal, in the form of a square wave with a variable duty cycle and/or variable frequency, is applied to Pin 1. In a typical system, input frequency is proportional to engine RPM. Duty cycle is proportional to the engine load. The circuits discussed are suitable for use in either open or closed loop systems. In closed loop systems, the engine exhaust is monitored and the air-to-fuel mixture is varied (via the duty cycle) to maintain a perfect, or stochiometric, ratio. INJECTORS Injectors and solenoids are available in a vast array of sizes and characteristics. Therefore, it is necessary to be able to design a drive system to suit each type of solenoid. The purpose of this section is to enable any system designer to use and modify the LM1949 and associated circuitry to meet the system specifications. Fuel injectors can usually be modeled by a simple RL circuit. Figure 19 shows such a model for a typical fuel injector. In actual operation, the value of L1 will depend upon the status of the solenoid. In other words, L1 will change depending upon whether the solenoid is open or closed. This effect, if pronounced enough, can be a valuable aid in determining the current necessary to open a particular type of injector. The change in inductance manifests itself as a breakpoint in the initial rise of solenoid current. The waveforms at the sense input show this occurring at approximately 130 mV. Thus, the current necessary to overcome the constrictive forces of that particular injector is 1.3 amperes. Figure 19. Model of a Typical Fuel Injector 6 Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 LM1949 www.ti.com SNLS349C – FEB 1995 – REVISED MARCH 2013 PEAK AND HOLD CURRENTS The peak and hold currents are determined by the value of the sense resistor RS. The driver IC, when initiated by a logic 1 signal at Pin 1, initially drives Darlington transistor Q1 into saturation. The injector current will rise exponentially from zero at a rate dependent upon L1, R1, the battery voltage and the saturation voltage of Q1. The drop across the sense resistor is created by the solenoid current, and when this drop reaches the peak threshold level, typically 385 mV, the IC is tripped from the peak state into the hold state. The IC now behaves more as an op amp and drives Q1 within a closed loop system to maintain the hold reference voltage, typically 94 mV, across RS. Once the injector current drops from the peak level to the hold level, it remains there for the duration of the input signal at Pin 1. This mode of operation is preferable when working with solenoids, since the current required to overcome kinetic and constriction forces is often a factor of four or more times the current necessary to hold the injector open. By holding the injector current at one fourth of the peak current, power dissipation in the solenoids and Q1 is reduced by at least the same factor. In the circuit of Figure 1, it was known that the type of injector shown opens when the current exceeds 1.3 amps and closes when the current then falls below 0.3 amps. In order to guarantee injector operation over the life and temperature range of the system, a peak current of approximately 4 amps was chosen. This led to a value of RS of 0.1Ω. Dividing the peak and hold thresholds by this factor gives peak and hold currents through the solenoid of 3.85 amps and 0.94 amps respectively. Different types of solenoids may require different values of current. The sense resistor RS may be changed accordingly. An 8-amp peak injector would use RS equal to .05Ω, etc. Note that for large currents above one amp, IR drops within the component leads or printed circuit board may create substantial errors unless appropriate care is taken. The sense input and sense ground leads (Pins 4 and 5 respectively), should be Kelvin connected to RS. High current should not be allowed to flow through any part of these traces or connections. An easy solution to this problem on double-sided PC boards (without plated-through holes) is to have the high current trace and sense trace attach to the RS lead from opposite sides of the board. TIMER FUNCTION The purpose of the timer function is to limit the power dissipated by the injector or solenoid under certain conditions. Specifically, when the battery voltage is low due to engine cranking, or just undercharged, there may not be sufficient voltage available for the injector to achieve the peak current. In the Figure 18 waveforms under the low battery condition, the injector current can be seen to be leveling out at 3 amps, or 1 amp below the normal threshold. Since continuous operation at 3 amps may overheat the injectors, the timer function on the IC will force the transition into the hold state after one time constant (the time constant is equal to RTx CT), or when the voltage on the TIMER pin (Pin 8) is greater than typically VSUPPLY x 63%. The timer is reset at the end of each input pulse. For systems where the timer function is not needed, it can be disabled by grounding the TIMER Pin (Pin 8). For systems where the initial peak state is not required, (i.e., where the solenoid current rises immediately to the hold level), the timer can be used to disable the peak function. This is done by setting the time constant equal to zero, (i.e., CT = 0). Leaving RT in place is recommended. The timer will then complete its timeout and disable the peak condition before the solenoid current has had a chance to rise above the hold level. The actual range of the timer in injection systems will probably never vary much from the 3.9 milliseconds shown in Figure 1. However, the actual useful range of the timer extends from microseconds to seconds, depending on the component values chosen. The useful range of RT is approximately 1k to 240k. The capacitor CT is limited only by stray capacitances for low values and by leakages for large values. The timing capacitor is reset (discharged) when the IN pin (Pin 1) is below the VOL(MIN) threshold. The capacitor reset time at the end of each controller pulse is determined by the supply voltage and the timing capacitor value. The IC resets the capacitor to an initial voltage (VBE) by discharging it with a current of approximately 15 mA. Thus, a 0.1 µF cap is reset in approximately 25 µs. COMPENSATION Compensation of the error amplifier provides stability for the circuit during the hold state. External compensation (from Pin 2 to Pin 3) allows each design to be tailored for the characteristics of the system and/or type of Darlington power device used. In the vast majority of designs, the value or type of the compensation capacitor is not critical. Values of 100 pF to 0.1 µF work well with the circuit of Figure 1. The value shown of 0.1 µF (disc) provides a close optimum in choice between economy, speed, and noise immunity. In some systems, increased phase and gain margin may be acquired by bypassing the collector of Q1 to ground with an appropriately rated 0.1 µF capacitor. This is, however, rarely necessary. Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 7 LM1949 SNLS349C – FEB 1995 – REVISED MARCH 2013 www.ti.com FLYBACK ZENER The purpose of zener Z1 is twofold. Since the load is inductive, a voltage spike is produced at the collector of Q1 anytime the injector is reduced. This occurs at the peak-to-hold transition, (when the current is reduced to one fourth of its peak value), and also at the end of each input pulse, (when the current is reduced to zero). The zener provides a current path for the inductive kickback, limiting the voltage spike to the zener value and preventing Q1 from damaging voltage levels. Thus, the rated zener voltage at the system peak current must be less than the minimum breakdown of Q1. Also, even while Z1 is conducting the majority of the injector current during the peak-to-hold transition (see Figure 20), Q1 is operating at the hold current level. This fact is easily overlooked and, as described in the following text, can be corrected if necessary. Since the error amplifier in the IC demands 94 mV across RS, Q1 will be biased to provide exactly that. Thus, the safe operating area (SOA) of Q1 must include the hold current with a VCE of Z1 volts. For systems where this is not desired, the zener anode may be reconnected to the top of RS as shown in Figure 21. Since the voltage across the sense resistor now accurately portrays the injector current at all times, the error amplifier keeps Q1 off until the injector current has decayed to the proper value. The disadvantage of this particular configuration is that the ungrounded zener is more difficult to heat sink if that becomes necessary. The second purpose of Z1 is to provide system transient protection. Automotive systems are susceptible to a vast array of voltage transients on the battery line. Though their duration is usually only milliseconds long, Q1 could suffer permanent damage unless buffered by the injector and Z1. There is one reason why a zener is preferred over a clamp diode back to the battery line, the other reason being long decay times. Figure 20. Circuit Waveforms 8 Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 LM1949 www.ti.com SNLS349C – FEB 1995 – REVISED MARCH 2013 Figure 21. Alternate Configuration for Zener Z1 POWER DISSIPATION The power dissipation of the system shown in Figure 1 is dependent upon several external factors, including the frequency and duty cycle of the input waveform to Pin 1. Calculations are made more difficult since there are many discontinuities and breakpoints in the power waveforms of the various components, most notably at the peak-to-hold transition. Some generalizations can be made for normal operation. For example, in a typical cycle of operation, the majority of dissipation occurs during the hold state. The hold state is usually much longer than the peak state, and in the peak state nearly all power is stored as energy in the magnetic field of the injector, later to be dumped mostly through the zener. While this assumption is less accurate in the case of low battery voltage, it nevertheless gives an unexpectedly accurate set of approximations for general operation. The following nomenclature refers to Figure 1. Typical values are given in parentheses: RS = Sense Resistor (0, 1Ω) VH = Sense Input Hold Voltage (.094V) VP = Sense Input Peak Voltage (.385V) VZ = Z1 Zener Breakdown Voltage (33V) VBATT = Battery Voltage (14V) L1 = Injector Inductance (.002H) R1 = Injector Resistance (1Ω) n = Duty Cycle of Input Voltage of Pin 1 (0 to 1) f = Frequency of Input (10 Hz to 200 Hz) Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 9 LM1949 SNLS349C – FEB 1995 – REVISED MARCH 2013 www.ti.com Q1 Power Dissipation: (1) SWITCHING INJECTOR DRIVER CIRCUIT The power dissipation of the system, and especially of Q1, can be reduced by employing a switching injector driver circuit. Since the injector load is mainly inductive, transistor Q1 can be rapidly switched on and off in a manner similar to switching regulators. The solenoid inductance will naturally integrate the voltage to produce the required injector current, while the power consumed by Q1 will be reduced. A note of caution: The large amplitude switching voltages that are present on the injector can and do generate a tremendous amount of radio frequency interference (RFI). Because of this, switching circuits are not recommended. The extra cost of shielding can easily exceed the savings of reduced power. In systems where switching circuits are mandatory, extensive field testing is required to guarantee that RFI cannot create problems with engine control or entertainment equipment within the vicinity. The LM1949 can be easily modified to function as a switcher. Accomplished with the circuit of Figure 23, the only additional components required are two external resistors, RA and RB. Additionally, the zener needs to be reconnected, as shown, to RS. The amount of ripple on the hold current is easily controlled by the resistor ratio of RA to RB. RB is kept small so that sense input bias current (typically 0.3 mA) has negligible effect on VH. Duty cycle and frequency of oscillation during the hold state are dependent on the injector characteristics, RA, RB, and the zener voltage as shown in the following equations. (2) 10 Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 LM1949 www.ti.com SNLS349C – FEB 1995 – REVISED MARCH 2013 As shown, the power dissipation by Q1 in this manner is substantially reduced. Measurements made with a thermocouple on the bench indicated better than a fourfold reduction in power in Q1. However, the power dissipation of the zener (which is independent of the zener voltage chosen) is increased over the circuit of Figure 1. Figure 22. Switching Application Circuit Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 11 LM1949 SNLS349C – FEB 1995 – REVISED MARCH 2013 www.ti.com Figure 23. LM1949 Simplified Internal Schematic 12 Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 LM1949 www.ti.com SNLS349C – FEB 1995 – REVISED MARCH 2013 REVISION HISTORY Changes from Revision B (March 2013) to Revision C • Page Changed layout of National Data Sheet to TI format .......................................................................................................... 12 Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated Product Folder Links: LM1949 13 PACKAGE OPTION ADDENDUM www.ti.com 27-May-2022 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) Samples (4/5) (6) LM1949N/NOPB ACTIVE PDIP P 8 40 RoHS & Green NIPDAU Level-1-NA-UNLIM -55 to 125 LM 1949N (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of