LM56 datasheet(7/13 Pages) NSC

7 / 13 page

Functional Description

1.0

PIN DESCRIPTION

This is the positive supply voltage pin. This pin

should be bypassed with 0.1 µF capacitor to

ground.

GND

This is the ground pin.

REF

This is the 1.250V bandgap voltage reference out-

put pin. In order to maintain trip point accuracy this

pin should source a 50 µA load.

TEMP

This is the temperature sensor output pin.

OUT1

This is an open collector digital output. OUT1 is ac-

tive LOW. It goes LOW when the temperature is

greater than T

1 and goes HIGH when the tempera-

ture drops below T

1–5˚C. This output is not in-

tended to directly drive a fan motor.

OUT2

This is an open collector digital output. OUT2 is ac-

tive LOW. It goes LOW when the temperature is

greater than the T

2 set point and goes HIGH when

the temperature is less than T

2–5˚C. This output is

not intended to directly drive a fan motor.

This is the input pin for the temperature trip point

voltage for OUT1.

This is the input pin for the low temperature trip

point voltage for OUT2.

DS012893-15

DS012893-16

VT1 = 1.250V x (R1)/(R1 + R2 + R3)

VT2 = 1.250V x (R1 + R2)/(R1 + R2 + R3)

where:

(R1+R2+R3) = 27k

Ω and

VT1 or T2 = [6.20 mV/˚C x T] + 395 mV therefore:

R1=VT1/(1.25V) x 27 kΩ

R2=(VT2/(1.25V) x 27 k)Ω–R1

R3=27 k

Ω −R1−R2

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