TLH5062

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 injec-

tor solenoid The current required to open a solenoid is sev-

eral times greater than the current necessary to merely hold

it open therefore the LM1949 by directly sensing the actu-

al solenoid current initially saturates the driver until the

‘‘peak’’ injector current is four times that of the idle or ‘‘hold-

ing’’ current

(Figure 3 – Figure 7) 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

a

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 fac-

tory for other package options)

Features

Y

Low voltage supply (3V – 55V)

Y

22 mA output drive current

Y

No RFI radiation

Y

Adaptable to all injector current levels

Y

Highly accurate operation

Y

TTLCMOS compatible input logic levels

Y

Short circuit protection

Y

High impedance input

Y

Y

Y

Externally set time-out

Y

Can be modified for full switching operation

Y

Available in plastic 8-pin miniDIP

Applications

Y

Fuel injection

Y

Throttle body injection

Y

Solenoid controls

Y

Air and fluid valves

Y

DC motor drives

Typical Application Circuit

TLH5062 – 1

FIGURE 1 Typical Application and Test Circuit

Order Number LM1949M or LM1949N

See NS Package Number M08A or N08E

C1995 National Semiconductor Corporation

RRD-B30M115Printed in U S A