1FEATURES

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

APPLICATIONS

• Fuel Injection

• Throttle Body Injection

• Solenoid Controls

• Air and Fluid Valves

• DC Motor Drives

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 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.

The LM1949 is available in the plastic PDIP, (contact

factory for other package options).