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LM1949 Injector Drive Controller

February 1995

LM1949 Injector Drive Controller
General Description
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 asolenoid 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 3– Figure 7). This guarantees opening of the injector. The current is then automatically reduced to the sufficient holdinglevel 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. The LM1949 is available in the plastic miniDIP, (contact factory for other package options).

n n n n n n n n n n n n n Low voltage supply (3V–5.5V) 22 mA output drive current No RFI radiationAdaptable 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 x IH) Externally set time-out Can be modified for full switching operation Available in plastic 8-pin minDIP

n n n n n Fuel injection Throttle body injection Solenoidcontrols Air and fluid valves DC motor drives

Typical Application Circuit


Order Number LM1949M or LM1949N See NS Package Number M08A or N08E FIGURE 1. Typical Application and Test Circuit

© 2001 National Semiconductor Corporation




Absolute Maximum Ratings

(Note 1)

Input Voltage Range Operating Temperature Range StorageTemperature Range Junction Temperature Lead Temp. (Soldering 10 sec.)

−0.3V to VCC −40˚C to +125˚C −65˚C to +150˚C 150˚C 260˚C

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Power Dissipation (Note 2) 8V 1235 mW

Electrical Characteristics
(VCC = 5.5V, VIN = 2.4V, TJ =25˚C, Figure 1, unless otherwise specified.) Symbol ICC Off Peak Hold VOH VOL IB IOP Input On Level Input Off Level Input Current Output Current Peak Hold VS VP VH t Sense Input Peak Threshold Hold Reference Time-out, t t ÷ RTCT VCC = 4.75V 350 88 90 386 94 100 415 102 110 mV mV % Pin 8 = 0V Pin 8 Open −10 −1.5 −22 −5 0.2 0.4 mA mA V Parameter Supply Current VIN = 0V Pin 8 = 0V Pin 8 Open VCC = 5.5VVCC = 3.0V VCC = 5.5V VCC = 3.0V 1.0 0.7 −25 11 28 16 1.4 1.2 1.35 1.15 3 +25 23 54 26 2.4 1.6 mA mA mA V V V V µA Conditions Min Typ Max Units

Output Saturation Voltage 10 mA, VIN = 0V

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Note 2: For operation in ambient temperatures above 25˚C, the device must be derated based on a 150˚C maximumjunction temperature and a thermal resistance of 100˚C/W junction to ambient.




Typical Circuit Waveforms






Schematic Diagram


FIGURE 2. LM1949 Circuit


Typical Performance Characteristics
Quiescent Current vs Supply Voltage Supply Current vs Supply Voltage...
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