NSC LM1946N, LM1946M Datasheet

February 1993

LM1946 Over/Under Current Limit Diagnostic Circuit

General Description

The LM1946 provides the industrial or automotive system designer with over or under current limit detection superior to that of ordinary transistor or comparator-based circuits.

Each of the five independent comparators can be used to monitor a separate load as either an over current or under current limit detector. Two comparators monitoring a single load can function as a current window monitor.

Current is sensed by monitoring the voltage drop across the wiring harness, pc board trace, or external sense resistor that feeds the load.

Provisions for compensating the user set limits for wiring harness resistance variations over temperature and supply voltage variations are also available.

When a limit is reached in one of the comparators, it turns on its output which can drive an external LED or microprocessor.

One side of the load can be grounded (not possible with

Features

Y

Five independent comparators

Y

Capable of 20 mA per output

Y

Low power drain

Y

User set input threshold voltages

Y

Reverse battery protection

Y

60V load dump protection on supply and all inputs

Y

Input common mode range exceeds V

Y

Short circuit protection

Y

Thermal overload protection

Y

Prove-out test pin

Y

Available in plastic DIP and SO packages

Applications

Y

Lamp fault detector

Y

Motor stall detector

Y

Power supply bus monitoring

ordinary comparator designs), which is important for automotive systems.

Typical Application CircuitÐLamp Fault Detector (I

CC

l

1A)

L

FIGURE 1

TL/H/8707– 2

C

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

TL/H/8707

Absolute Maximum Ratings

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

Supply Voltage (V

Survival Voltage (T

and Input Pins)

CC

s

100 ms)

b

50V toa60V

Operational Voltage 9V to 26V

Internal Power Dissipation (Note 1) Internally Limited

s

Electrical Characteristics 9V

s

V

16V, Isete20 mA, T

CC

Parameter Conditions Min Typ Max Units

Quiescent Current All Outputs ‘‘Off’’ 1.40 3.00 mA

Reference Voltage I

Reference Voltage 9VsV Line Regulation

e

10 mA 5.8 6.4 7.0 V

ref

CC

s

16V, I

e

ref

Iset Voltage Isete20 mA 1.20 1.40 1.60 V

Input Offset Voltage At Output Switch Point. V

Input Offset Current I

Input Bias Current I

9VsV

IN(a)

b

or I

CM

s

I

IN(b)

16V

,9VsV

CM

Input Common Mode Voltage Range

Maximum Positive Either Input. Ts100 ms Input Transient

Maximum Negative Either Input. Ts100 ms Input Transient

Output Saturation I Voltage

Output Short Circuit V Current

Output Leakage Current V

e

2 mA, 9VsV

O

e

I

10 mA, 9VsV

O

e

0Vdc, Comparator ‘‘ON’’

O

e

0Vdc. Comparator ‘‘Off’’ 0.01 1.00 mA

O

CC

s

Test Threshold At Switch Point on Any Output Voltage V

e

O

2V (Note 2)

Test Threshold Current

Note 1: Thermal resistance from junction to ambient is typically 53§C/W (board mounted).

Note 2: The test pin is an active high input, i.e. all five will be forced high when this pin is driven high.

Note 3: C

ESD

e

100 pF, R

ESD

e

1.5k

Output Short Circuit to Ground or V

Operating Temperature Range (TA)

CC

Continuous

b

40§Ctoa85§C

Maximum Junction Temperature

Storage Temperature Range

b

65§Ctoa150§C

Lead Temperature (Soldering, 10 sec.)

ESD Susceptibility (Note 3) 600V

e

25§C (unless otherwise specified)

j

10 mA

e

2V

O

s

16V

s

16V 18.00 20.00 22.00 mA

g

5

g

1.0

g

0.10

g

50 mV

g

5.0 mV

g

1.00 mA

4.00 26.0 V

60 70 V

b

50

b

60 V

16V 0.80 1.00 V

16V 1.00 1.20 V

20 45 120.0 mA

0.80 1.25 2.00 V

0.2 mA

a

150§C

260§C

dc

2

Connection Diagram

Order Number LM1946N or LM1946M

See NS Package Number M20B or N20A

Typical Test Circuit

Simplified Comparator Schematic

TL/H/8707– 20

TL/H/8707– 23

TL/H/8707– 24

3

Typical Performance Characteristics

V

sat

Peak I

vs I

Quiescent Current

O

vs V

O

CC

vs V

CC

V

vs Temperature V

set

Quiescent Current vs V

CC

vs Temperature

ref

Iset vs Temperature Iset vs Temperature Iset vs Temperature

Test Threshold Common Mode Lower Limit

4

TL/H/8707– 4