2002 Microchip Technology Inc.
DS21439B-page 1
TC620/TC621
Features
User Programmable Hysteresis and
Temperature Set Point
Easily Programs with 2 External Resistors
Wide Temperature Detection Range:
-0C to 70C: (TC620/TC621CCX)
-40C to +125C: (TC620/TC621CVX)
-40C to +85C: (TC620/TC621CEX)
-55C to +125C: (TC620/TC621CMX)
Onboard Temperature Sensing Applications
(TC620X)
External NTC Thermistor for Remote Sensing
Applications (TC621X)
Available in 8-Pin PDIP and SOIC Packages
Applications
Power Supply Over Temperature Detection
Consumer Equipment
Temperature Regulators
CPU Thermal Protection
Device Selection Table
NOTE: *The part code will be C or H.
(See Functional Block Diagrams).
Package Type
General Description
The TC620 and TC621 are programmable logic output
temperature detectors designed for use in thermal
management applications. The TC620 features an
onboard
temperature
sensor,
while
the
TC621
connects to an external NTC thermistor for remote
sensing applications.
Both devices feature dual thermal interrupt outputs
(HIGH LIMIT and LOW LIMIT), each of which is pro-
grammed with a single external resistor. On the TC620,
these outputs are driven active (high) when measured
temperature equals the user programmed limits. The
CONTROL (hysteresis) output is driven high when tem-
perature equals the high limit setting and returns low
when temperature falls below the low limit setting. This
output can be used to provide ON/OFF control to a
cooling fan or heater. The TC621 provides the same
output functions except that the logical states are
inverted.
The
TC620/TC621
are
usable
over
operating
temperature ranges of 0C to 70C, -40C to +125C
and -55C to 125C.
Part Number
Package
Temperature
Range
TC620X*COA
8-Pin SOIC
0C to +70C
TC620X*CPA
8-Pin PDIP
0C to +70C
TC620X*EOA
8-Pin SOIC
-40C to +85C
TC620X*EPA
8-Pin PDIP
-40C to +85C
TC620C*VOA
8-Pin SOIC
-40C to +125C
TC621X*COA
8-Pin SOIC
0C to +70C
TC621X*CPA
8-Pin PDIP
0C to +70C
TC621X*EOA
8-Pin SOIC
-40C to +85C
TC621X*EPA
8-Pin PDIP
-40C to +85C
THERMISTOR
8-SOIC
8-SOIC
VDD
GND
LOW LIMIT
CONTROL
NC
LOW SET
HIGH SET
HIGH LIMIT
VDD
GND
LOW LIMIT
CONTROL
LOW SET
HIGH SET
HIGH LIMIT
8
7
6
5
1
2
3
4
TC621XCOA
TC621XEOA
8
7
6
5
1
2
3
4
TC620XCOA
TC620XEOA
TC620CVOA
THERMISTOR
8-PDIP
VDD
GND
LOW LIMIT
CONTROL
LOW SET
HIGH SET
HIGH LIMIT
8
7
6
5
1
2
3
4
TC621XCPA
TC621XEPA
NC
8-PDIP
VDD
GND
LOW LIMIT
CONTROL
HIGH SET
LOW SET
HIGH LIMIT
8
7
6
5
1
2
3
4
TC620XCPA
TC620XEPA
5V, Dual Trip Point Temperature Sensors
TC620/TC621
DS21439B-page 2
2002 Microchip Technology Inc.
Functional Block Diagrams
3
HIGH SET
2
LOW SET
5
CONTROL*
6
HIGH LIMIT
VDD
7
LOW LIMIT
8
4
*Suffix code "C" denotes cooling option (High true CONTROL output).
Suffix code "H" denotes heating option (Low true CONTROL output).
Q
S
R
Q
+
+
TC620
HIGH SET
LOW SET
1
THERMISTOR
CONTROL*
HIGH LIMIT
LOW LIMIT
Temp. to
Voltage
Converter
VREF
GEN
VREF
GEN
VREF
3
2
5
6
VDD
7
8
4
Q
S
R
Q
+
+
TC621
Thermistor
Interface
Circuit
VREF
GEN
VREF
GEN
VREF
2002 Microchip Technology Inc.
DS21439B-page 3
TC620/TC621
1.0
ELECTRICAL
CHARACTERISTICS
Absolute Maximum Ratings*
Supply Voltage ....................................................... 20V
Input Voltage Any Input .. (GND 0.3V) to (V
DD
+0.3V)
Package Power Dissipation (T
A
70C)
PDIP .............................................. 730mW
SOIC .............................................. 470mW
Derating Factors:
Plastic ........................................... 8mW/C
Operating Temperature:
M Version......................... -55C to +125C
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.
TC620/TC621 ELECTRICAL SPECIFICATIONS
Electrical Characteristics: T
A
= 25C, unless otherwise specified.
Symbol
Parameter
Min
Typ
Max
Unit
Test Conditions
V
DD
Supply Voltage Range
4.5
--
18
V
I
DD
Supply Current
--
270
400
A
5V
V
DD
18V
R
OUT
Output Resistance
--
400
1000
W
Output High or Low, 5V
V
DD
18V
I
OUT
Output Current
--
--
1
mA
Temp Sensed
Source/Sink
I
OUT
Output Current
--
--
1
mA
Cool/Heat
Source/Sink
T
ERR
Absolute Accuracy
T - 3
T
T + 3
C
T = Programmed Temperature
TC620/TC621
DS21439B-page 4
2002 Microchip Technology Inc.
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
PIN FUNCTION TABLE
Pin No.
(8-Pin PDIP)
(8-Pin SOIC)
0C to +70C
-40C to +85C
-40C to +125C
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
DD
Power supply input.
Pin No.
(8-Pin PDIP)
(8-Pin SOIC)
0C to +70C
-40C to +85C
Symbol
Description
1
THERMISTOR
Thermistor input.
2
HIGH SET
High temperature set point. Connect an external 1% resistor from HIGH SET to
V
DD
to set trip point.
3
LOW SET
Low temperature set point. Connect an external 1% resistor from LOW SET to
V
DD
to set trip point.
4
GND
Ground Terminal.
5
CONTROL
Control output.
6
LOW LIMIT
Low temperature push/pull output.
7
HIGH LIMIT
High temperature push/pull output.
8
V
DD
Power supply input.
2002 Microchip Technology Inc.
DS21439B-page 5
TC620/TC621
3.0
DETAILED DESCRIPTION
The TC620 has a positive temperature coefficient tem-
perature sensor and a dual threshold detector. Temper-
ature set point programming is accomplished with
external resistors from the HIGH SET and LOW SET
inputs to V
DD.
The HIGH LIMIT and LOW LIMIT outputs
remain low as long as measured temperature is below
set point values. As measured temperature increases,
the LOW LIMIT output is driven high when temperature
equals the LOW SET set point (3C max). If tempera-
ture continues to climb, the HIGH LIMIT output is driven
high when temperature equals the HIGH SET set point
(Figure 3-1). The CONTROL (hysteresis) output is
latched in its active state at the temperature specified
by the HIGH SET resistor. CONTROL is maintained
active until temperature falls to the value specified by
the LOW SET resistor.
FIGURE 3-1:
TC620/TC621 INPUT VS.
OUTPUT LOGIC
3.1
Programming the TC620
The resistor values to achieve the desired trip point
temperatures on HIGH SET and LOW SET are
calculated using Equation 3-1:
EQUATION 3-1:
For example, a 50C setting on either the HIGH SET
or LOW SET input is calculated using Equation 3-2 as
follows:
EQUATION 3-2:
Care must be taken to ensure the LOW SET program-
ming resistor is a smaller value than the HIGH SET
programming resistor. Failure to do this will result in
erroneous operation of the CONTROL output.
Care must also be taken to ensure the LOW SET
temperature setting is at least 5C lower than the HIGH
SET temperature setting.
Figure 3-2 can help the user obtain an estimate of the
external resistor values required for the desired LOW
SET and HIGH SET trip points.
FIGURE 3-2:
TC620 SENSE
RESISTORS VS. TRIP
TEMPERATURE
3.2
Built-in Hysteresis
To
prevent
output
"chattering"
when
measured
temperature is at (or near) the programmed trip point
values, the LOW SET and HIGH SET inputs each have
built-in hysteresis of -2C below the programmed
settings (Figure 3-3).
FIGURE 3-3:
BUILT-IN HYSTERESIS ON
LOW LIMIT AND HIGH
LIMIT OUTPUTS
As shown, the outputs remain in their active state
(hysteresis) until temperature falls an additional 2C
below the user's setting.
Low Set Point
High Set Point
Low Limit Output
High Limit Output
Control Output (Cool Option
Control Output (Heat Option)
Temperature
R
TRIP
= 0.5997 x T
2.1312
Where:
R
TRIP
= Programming resistor in Ohms
T = The desired trip point temperature in degrees
Kelvin.
R
SET
= 0.5997 x ((50 + 273.15)
2.1312
) = 133.6k
TEMPERATURE (C)
RESISTANCE, R
TRIP
(k
)
-55
-35
-15
5
25
45
65
85
105
125
50
100
150
200
250
Set Point
(Set Point 2C)
High Limit
or Low Limit
Output
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