2002 Microchip Technology Inc.
DS21441B-page 1
TC623
Features
Integrated Temp Sensor and Detector Operate
from a Supply Voltage as Low as 2.7V
Replaces Mechanical Thermostats and Switches
On-Chip Temperature Sense
8-Pin DIP or SOIC for Direct PCB Mounting
2 User Programmable Temperature Set Points
2 Independent Temperature Limit Outputs
Heat/Cool Regulate Output
Applications
CPU Thermal Management
System Over or Under Temperature Shutdown
Advanced Thermal Warning
Fan Speed Control Circuits
Accurate Appliance Temperature Sensing
Environmental Control
Device Selection Table
Functional Block Diagram
Package Type
General Description
The TC623 is a 3V solid-state, programmable temper-
ature sensor designed for use in thermal management
applications. It features dual thermal interrupt outputs
(LOW LIMIT and HIGH LIMIT) each of which are set
with an external resistor. The HIGH LIMIT and LOW
LIMIT outputs are driven active (high) when measured
temperature equals the user programmed limits. The
CONTROL output is driven active (high) when temper-
ature equals the HIGH LIMIT set point and turned off
when temperature falls below the LOW LIMIT set point.
The CONTROL output can be used to provide simple
ON/OFF control to a cooling fan if so desired.
Low voltage operation, easy set point programming,
small size and low cost make the TC623 an ideal
choice for many thermal management applications.
Part Number
Package
Temp. Range
TC623CCOA
8-Pin SOIC
0C to +70C
TC623CCPA
8-Pin PDIP
0C to +70C
TC623CEOA
8-Pin SOIC
-40C to +85C
TC623CEPA
8-Pin PDIP
-40C to +85C
TC623CVOA
8-Pin SOIC
-40C to +125C
NOTE: Latch Output (C option), is a Standard Device. Con-
tact Factory for Latch Q Output (H option).
3
HIGH SET
2
LOW SET
1
NC
4
GND
5
CONTROL
6
HIGH LIMIT
V
CC
7
LOW LIMIT
8
Latch
Q
S
R
+
+
TC623
R < R
LOW
HIGH
V
REF
Gen.
V
REF
Gen.
V
REF
Temperature
To Voltage
Converter
GND
HIGH SET
PDIP
SOIC
NC
GND
HIGH SET
LOW SET
LOW SET
NC
V
CC
HIGH LIMIT
CONTROL
LOW LIMIT
V
CC
HIGH LIMIT
CONTROL
LOW LIMIT
8
7
6
5
1
2
3
4
1
8
2
7
3
6
4
5
TC623CCOA
TC623CEOA
TC623CVOA
TC623CCPA
TC623CEPA
3V, Dual Trip Point Temperature Sensor
TC623
DS21441B-page 2
2002 Microchip Technology Inc.
1.0
ELECTRICAL
CHARACTERISTICS
Absolute Maximum Ratings*
Supply Voltage ......................................................5.5V
Input Voltage Any Input .. (GND 0.3V) to (V
DD
+0.3V)
Package Power Dissipation (T
A
70C)
Plastic DIP .............................................730mW
SOIC......................................................470mW
Derating Factors
Plastic DIP ............................................8mW/C
SOIC .....................................................6mW/C
Operating Temperature
V Version ................................. -40C to +125C
E Version ................................... -40C to +85C
C Version ...................................... 0C to +70C
Storage Temperature.......................... -65C to +150C
*Stresses above those listed under "Absolute Maximum Rat-
ings" may cause permanent damage to the device. These are
stress ratings only and functional operation of the device at
these or any other conditions above those indicated in the
operation sections of the specifications is not implied. Expo-
sure to Absolute Maximum Rating conditions for extended
periods may affect device reliability.
TC623 ELECTRICAL SPECIFICATIONS
Electrical Characteristics: Over Operating Temperature Range, V
DD
= 2.7V to 4.5V, unless otherwise specified.
Symbol
Parameter
Min
Typ.
Max
Unit
Test Conditions
V
DD
Supply Voltage Range
2.7
--
4.5
V
I
DD
Supply Current
--
150
250
A
2.7V
V
DD
4.5V
T
SET
Absolute Accuracy
T - 3
T 1
T + 3
C
T = Programmed Temperature
V
OH
Output Voltage High
0.9 x V
DD
0.8 x V
DD
--
--
--
--
V
V
I
OH
= 250
A
I
OH
= 500
A
V
OL
Output Voltage Low
--
--
--
--
0.1 x V
DD
0.2 x V
DD
V
V
I
OL
= 500
A
I
OL
= 1mA
HYS
Hysteresis
--
--
-2
C
Falling Temperature
2002 Microchip Technology Inc.
DS21441B-page 3
TC623
2.0
PIN DESCRIPTION
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
PIN FUNCTION TABLE
Pin No.
(8-Pin SOIC)
(8-Pin PDIP)
Symbol
Description
1
NC
No Internal Connection.
2
LOW SET
Low temperature set point. Connect an external 1% resistor from LOW SET to V
DD
to set trip point.
3
HIGH SET
High temperature set point. Connect an external 1% resistor from HIGH SET to
V
DD
to set trip point.
4
GND
Ground Terminal.
5
CONTROL
Control output.
6
HIGH LIMIT
High temperature push/pull output.
7
LOW LIMIT
Low temperature push/pull output.
8
V
CC
Power supply input.
TC623
DS21441B-page 4
2002 Microchip Technology Inc.
3.0
DETAILED DESCRIPTION
3.1
TC623 Operation
The TC623 has a positive temperature coefficient
(Silicon) temperature sensor and dual threshold detec-
tor. Temperature set point programming is accom-
plished with external resistors from the HIGH SET and
LOW SET inputs to V
CC
. The HIGH LIMIT and LOW
LIMIT outputs remain inactive (low) as long as the
measured temperature is below set point values. As
temperature increases, the LOW LIMIT is driven high
when temperature equals the LOW LIMIT set point
(3C). If temperature continues to climb, the HIGH
LIMIT output is driven high when temperature equals
the HIGH LIMIT set point (3C).
Figure 3-1 shows the relationship between the sense
resistance values and trip point temperature.
FIGURE 3-1:
TC623 SENSE
RESISTORS VS. TRIP
TEMPERATURE
The CONTROL output is driven high when the HIGH
LIMIT output goes high and is RESET low when the
LOW LIMIT output goes low. This output provides the
logic for simple ON/OFF fan control. Figure 3-2 shows
overall TC623 operation.
FIGURE 3-2:
TC623 TEMPERATURE
VS. OUTPUT
To prevent output "chattering" when measured temper-
ature is at (or near) the trip point values, the LOW SET
and HIGH SET inputs each have a built-in hysteresis of
-2C max. As a result, the HIGH LIMIT and LOW LIMIT
outputs remain active until the measured temperature
falls a maximum of 2C below the programmed HIGH
SET and LOW SET thresholds as shown in Figure 3-3.
The programmed setting threshold of Figure 3-3 is user
programmed temperature trip points of either the LOW
SET or HIGH SET inputs. The LOW LIMIT or HIGH
LIMIT output is driven active when temperature equals
the set point value (to within 3C). The output remains
active until the temperature falls an additional 2C
below the set point due to hysteresis.
FIGURE 3-3:
HIGH SET AND LOW SET
THRESHOLDS
TEMPERATURE (C)
RESISTANCE, R
TRIP
(k
)
-55
-35
-15
5
25
45
65
85
105
125
50
100
150
200
250
Low Set Point
High Set Point
Low Limit Output
High Limit Output
Control Output (Cool Option)
Temperature
Programmed Setpoint
-2C Hysteresis
High Limit or Low Limit Ouput
2002 Microchip Technology Inc.
DS21441B-page 5
TC623
4.0
TYPICAL APPLICATIONS
4.1
Mounting
If the TC623 is used to measure the temperature of
another device, it is important that the top surface of the
TC623 package be in intimate contact with the
measured device. Good thermal conductivity and no air
space is critical to accurate temperature measurement
in applications of this type.
4.2
Trip Point Programming
The resistance values required for the HIGH SET and
LOW SET inputs are calculated using the formula
below:
For example, to program a trip point of 50C, the pro-
gramming resistor is:
R
TRIP
= 0.5997 x T
2.1312
Where;
R
TRIP
= Programming resistor value in Ohms
T = Desired trip temperature in degrees Kelvin.
R
TRIP
= 0.5997 x (50 + 273.15)
2.1312
) = 133.65k
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