LM56 National Semiconductor, LM56 Datasheet - Page 7

• Manufacturer Part Number: LM56
• Description: Dual Output Low Power Thermostat
• Manufacturer: National Semiconductor

Functional Description
1.0 PIN DESCRIPTION
V
GND
V
V
OUT1
OUT2
V
V
+
REF
TEMP
T1
T2
This is the positive supply voltage pin. This pin
should be bypassed with 0.1 µF capacitor to
ground.
This is the ground pin.
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.
This is the temperature sensor output pin.
This is an open collector digital output. OUT1 is ac-
tive LOW. It goes LOW when the temperature is
greater than T
ture drops below T
tended to directly drive a fan motor.
This is an open collector digital output. OUT2 is ac-
tive LOW. It goes LOW when the temperature is
greater than the T
the temperature is less than T
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.
1
and goes HIGH when the tempera-
2
set point and goes HIGH when
1
–5˚C. This output is not in-
2
–5˚C. This output is
7
V
V
where:
(R1 + R2 + R3) = 27 k
V
R1 = V
R2 = (V
R3 = 27 k
T1
T2
T1 or T2
= 1.250V x (R1)/(R1 + R2 + R3)
= 1.250V x (R1 + R2)/(R1 + R2 + R3)
T1
T2
/(1.25V) x 27 k
= [6.20 mV/˚C x T] + 395 mV therefore:
/(1.25V) x 27 k) –R1
− R1 − R2
and
DS012893-15
www.national.com
DS012893-16