LM1946N National Semiconductor, LM1946N Datasheet - Page 9

• Manufacturer Part Number: LM1946N
• Description: IC DIAGNOSTIC CIRCUIT 20 DIP
• Manufacturer: National Semiconductor

Specifications of LM1946N

• Function: Current Sense
• Voltage - Input: 9 ~ 26 V
• Current - Output: 20mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Through Hole
• Package / Case: 20-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Accuracy: -
• Sensing Method: -
• Other names: *LM1946N; LM1946

ures 13 and 14 ) The outputs can also be wired-or together
Application Hints
THE OUTPUT SECTION
The output section of the LM1946 is different from most
automotive comparators as it employs high beta proprietary
PNP transistors which are very rugged and capable of high-
er output currents Each of the five comparator outputs is
capable of at least 20 mA of drive and are internally current
limited and protected against supply overvoltage The
LM1946 is therefore capable of driving LED’s directly and
larger bulbs via an external grounded base NPN (see Fig-
without harm
For use in systems with a microprocessor flag instead of a
dashboard indicator the LM1946 can be powered by a stan-
dard 5V logic supply This prevents the LM1946 output from
swinging above the microprocessor supply which might
cause latch problems Since the input common mode range
is independent of supply the inputs can still operate at any
level up to 26V Since the outputs can source current only
pull-down resistors as in Figure 15 are required their value
depending on the input drive requirements of the particular
microprocessor used When operating with a V
less than 7V it is important to connect the V
This forces V
internal circuitry
FIGURE 12 Comparator Input Stage
REF
to a fixed voltage which is used for bias of
FIGURE 13
(Continued)
TL H 8707 – 19
REF
TL H 8707 – 13
pin to V
CC
supply
CC
9
TEST PIN
The test pin is a high impedance logic input Forcing this pin
high (
used to test the indicator LED display (or other output load)
The usual application circuit connects this pin to the ignition
crank line During engine crank therefore the LM1946 out-
put display will light similar to the usual dashboard indica-
tors The test pin was designed to operate with the usual
transient voltages found on the crank line as long as a limit-
ing resistor (e g 30k) separates them (Figure 1)
Minimum pulse width (ms)
t
2V) forces all five comparator outputs on This is
FIGURE 14
FIGURE 15
0 01
a
1 5 C1 ( F)
TL H 8707 – 14
TL H 8707 – 15