TLH12372

August 1995

LM9040

Dual Lambda Sensor Interface Amplifier

General Description

The LM9040 is a dual sensor interface circuit consisting of

two independent sampled input differential amplifiers de-

signed for use with conventional Lambda Oxygen Sensors

The Lambda Sensor is used for monitoring the oxygen con-

centration in the exhaust of gasoline engines using catalytic

after treatment and will deliver a voltage signal which is de-

pendent on the air-fuel mixture The gain of the amplifiers

are internally set and can directly convert the Lambda sen-

sor output voltage to a level suitable for AD conversion in a

system using a 5V reference

The input common mode voltage range of each amplifier is

g

2V with respect to the IC ground pin This will allow the IC

to connect to sensors which are remotely grounded at the

engine exhaust manifold or exhaust pipe

Each amplifier is capable of independent default operation

should either or both of the leads to a sensor become

open circuited

Noise filtering is provided by an internal switched capacitor

low pass filter as part of each amplifier and by external

components

The LM9040 is fully specified over the automotive tempera-

Small Outline surface mount package

Features

Y

Single 5V supply operation

Y

Y

Differential input voltage range of 50 mV to 950 mV

Y

Sampled differential input

Y

Switched capacitor low pass filter

Y

Y

Open input default operation

Y

Cold sensor default operation

Y

Low power consumption (42 mW max)

Y

Gain set by design and guaranteed over the operating

temperature range

Applications

Y

Closed loop emissions control

Y

Catalytic converter monitoring

Connection Diagram

TLH12372 – 1

Top View

Ordering Information

LM9040M

See NS Package Number M14B

C1995 National Semiconductor Corporation

RRD-B30M115Printed in U S A