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LM1949

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SNLS349C –FEB 1995–REVISED MARCH 2013

LM1949 Injector Drive Controller

Check for Samples: LM1949

FEATURES

DESCRIPTION

The LM1949 linear integrated circuit serves as an

• Low Voltage Supply (3V–5.5V)

excellent control of fuel injector drive circuitry in

• 22 mA Output Drive Current

modern automotive systems. The IC is designed to

• No RFI Radiation

control an external power NPN Darlington transistor

that drives the high current injector solenoid. The

• Adaptable to All Injector Current Levels

current required to open a solenoid is several times

• Highly Accurate Operation

greater than the current necessary to merely hold it

• TTL/CMOS Compatible Input Logic Levels

open; therefore, the LM1949, by directly sensing the

actual solenoid current, initially saturates the driver

• Short Circuit Protection

until the “peak” injector current is four times that of

• High Impedance Input

the idle or “holding” current (Figure 19–Figure 22).

• Externally Set Holding Current, I

This guarantees opening of the injector. The current

is then automatically reduced to the sufficient holding

• Internally Set Peak Current (4 × I

)

level for the duration of the input pulse. In this way,

• Externally Set Time-Out

the total power consumed by the system is

• Can be Modified for Full Switching Operation

dramatically reduced. Also, a higher degree of

• Available in Plastic 8-Pin PDIP

correlation of fuel to the input voltage pulse (or duty

cycle) is achieved, since opening and closing delays

of the solenoid will be reduced.

APPLICATIONS

Normally powered from a 5V ± 10% supply, the IC is

• Fuel Injection

typically operable over the entire temperature range

• Throttle Body Injection

(−55°C to +125°C ambient) with supplies as low as 3

• Solenoid Controls

volts. This is particularly useful under “cold crank”

• Air and Fluid Valves conditions when the battery voltage may drop low

enough to deregulate the 5-volt power supply.

• 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

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.

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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.

Summary of content (17 pages)

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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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).
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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.
PAGE 10
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.
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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.
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LM1949 SNLS349C – FEB 1995 – REVISED MARCH 2013 www.ti.com Figure 23.
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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 ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
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