NSC LM1949N Datasheet

LM1949 Injector Drive Controller

LM1949 Injector Drive Controller

February 1995

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 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 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.

Normally powered from a 5V
cally operable over the entire temperature range (

a

125§C ambient) with supplies as low as 3 volts. This is

g

10% supply, the IC is typi-

b

55§Cto

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).

Typical Application Circuit

Features

Y

Low voltage supply (3V– 5.5V)

Y

22 mA output drive current

Y

No RFI radiation

Y

Adaptable to all injector current levels

Y

Highly accurate operation

Y

TTL/CMOS compatible input logic levels

Y

Short circuit protection

Y

High impedance input

Y

Externally set holding current, I

Y

Internally set peak current (4cIH)

Y

Externally set time-out

Y

Can be modified for full switching operation

Y

Available in plastic 8-pin miniDIP

H

Applications

Y

Fuel injection

Y

Throttle body injection

Y

Solenoid controls

Y

Air and fluid valves

Y

DC motor drives

FIGURE 1. Typical Application and Test Circuit

TL/H/5062– 1

Order Number LM1949M or LM1949N

See NS Package Number M08A or N08E

COPSTMis a trademark of National Semiconductor Corporation.

C

1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.

TL/H/5062

Absolute Maximum Ratings

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.

Supply Voltage 8V

Power Dissipation (Note 1) 1235 mW

Input Voltage Range

Operating Temperature Range

Storage Temperature Range

b

0.3V to V

b

40§Ctoa125§C

b

65§Ctoa150§C

CC

Junction Temperature 150§C

Lead Temp. (Soldering 10 sec.) 260§C

Electrical Characteristics (V

CC

e

5.5V, V

IN

e

2.4V, T

j

e

25§C,

Figure 1

, unless otherwise specified.)

Symbol Parameter Conditions Min Typ Max Units

I

CC

Supply Current

Off V
Peak Pin 8

e

0V 11 23 mA

IN

e

0V 28 54 mA

Hold Pin 8 Open 16 26 mA

V

OH

V

OL

I

B

I

OP

V

S

Input On Level V

Input Off Level V

Input Current

Output Current

Output Saturation Voltage 10 mA, V

Peak Pin 8
Hold Pin 8 Open

e

5.5V 1.4 2.4 V

CC

e

V

3.0V 1.2 1.6 V

CC

e

5.5V 1.0 1.35 V

CC

e

V

3.0V 0.7 1.15 V

CC

b

25 3

e

0V

e

0V 0.2 0.4 V

IN

b

10

b

1.5

b

22 mA

b

5mA

a

25 mA

Sense Input

V

p

V

H

Peak Threshold V
Hold Reference 88 94 102 mV

t Time-out, t tdRTC

NOTE 1: 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.

§

e

4.75V 350 386 415 mV

CC

T

90 100 110 %

Typical Circuit Waveforms

TL/H/5062– 2

2

Schematic Diagram

TL/H/5062– 3

FIGURE 2. LM1949 Circuit

3