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MCP9502PT-065E/OT

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
© 2011 Microchip Technology Inc. DS22268A-page 7
MCP9501/2/3/4
NOTES:
MCP9501/2/3/4
DS22268A-page 8 © 2011 Microchip Technology Inc.
4.0 FUNCTIONAL DESCRIPTION
The MCP9501/2/3/4 temperature switch family
integrates a thermal diode, a comparator, and a factory
selectable resistive network used to set the
temperature thresholds. The available output
thresholds range from -35°C to 125°C at 10°C
increments. There is no additional configuration
required to operate this device. The selectable output
hysteresis is controlled using a single input pin. When
this pin is connected to ground, the output hysteresis is
2°C (typical) and when connected to V
DD
the output
hysteresis is 10°C (typical). Figure 4-1 shows the
functional block diagram.
FIGURE 4-1: Functional Block Diagram.
There are two output configurations for this family, a
push-pull and an open-drain output with active-high
and active-low assertions. These assertion options are
referred to as Cold and Hot options, primarily due to the
direction of selected hysteresis. For the Cold option,
temperature has to fall below the threshold for the
output to assert High, and de-assert Low when the
temperature rises above the threshold plus the
hysteresis. For example, a 65°C threshold and 2°C
(typical) hysteresis, when temperature falls below 65°C
the output asserts High, and the de-asserts Low when
temperature rises above 67°C. For the Hot option, the
opposite is true. When temperature rises above 65°C,
the output asserts Low, and de-asserts High when the
temperature falls below 63°C. Figure 4-2 shows a
graphical description for the Hot and Cold options.
FIGURE 4-2: Output Hysteresis.
The Push-Pull output is ideal for a microcontroller
interface using an input/output pin or an interrupt input
pin. The open-drain option can be used with multiple
sensors in a wired-OR configuration or as a level
shifter.
I
SET
R
x
+
-
OUT/
OUT
Thermal
Diode
Hysteresis
Select Pin
Threshold
Select
Cold
Hot
T
SET
T
HYST
Temperature
V
Output
10°C Typical Hysteresis
2°C Typical
Hysteresis
Cold
Hot
T
SET
T
HYST
Temperature
V
Output
10°C Typical Hysteresis
2°C Typical
Hysteresis
Hot-Option (Active-Low)
Cold-Option (Active-High)
© 2011 Microchip Technology Inc. DS22268A-page 9
MCP9501/2/3/4
4.1 Application Information
The MCP9501/2/3/4 temperature switch family
integrates a temperature sensor and a comparator
circuit which outputs an alert signal when the factory
set temperature threshold is exceeded. No additional
component is required for device operation, which
provides simplicity to the system designer. The device
output options provide design flexibility for various
applications such as overtemperature protection circuit
or a closed loop temperature control unit. This device
can be interfaced to a closed loop fan controller
network without the need for a microcontroller.
FIGURE 4-3: Fan Controller Using
MCP9502.
The MCP9501/2/3/4 provide Open-Drain output where
multiple sensors from multiple PCB hot-spots can be
connected to a single processor I/O input with a wired-
OR configuration. The MCP9501 requires an external
pull-up resistor which can be used to level-shift the alert
signal. For example, if the sensors are powered with
5V
DD
and the controller or processor is powered with
3V
DD
, the external resistor can be level-shifted by
connecting 3V
DD
to the pull-up resistor as shown in
Figure 4-4.
FIGURE 4-4: MCP9501 Wired-OR Output
Configuration with Level-shift.
4.1.1 LAYOUT CONSIDERATION AND
THERMAL CONSIDERATION
This family of sensors measures temperature by
monitoring the voltage level of a thermal diode located
in the die. A low-impedance thermal path between the
die and the PCB is provided by the pins. Therefore, the
sensor effectively monitors PCB temperature. For
efficient performance, it is recommended to layout the
device as close to the heat source as possible.
When connecting an external resistor to the MCP9501/
3, the current through the pull-up resistor must be
considered to prevent self-heat due to power. This can
be determined using Equation 4-1.
EQUATION 4-1: EFFECT OF
SELF-HEATING
For example, at room temperature, when the output
asserts Active-Low and maximum I
DD
= 50 µA,
V
DD
=5.5V, V
OL
= 0.3V and I
OUT
= 5 mA (see the
specification table), the self heating due to power
dissipation (T
J
- T
A
) is ~0.4°C.
Output
HYST
5V
DD
MCP9502
12V
M
OUT
HYST
5V
DD
OUT
HYST
5V
DD
I/O
R
PULL_UP
Micro-
controller
MCP9501
85°C
MCP9503
35°C
3V
DD
Where:
T
J
= Junction Temperature
T
A
= Ambient Temperature
θ
JA
= Package Thermal Resistance
(220.7 °C/W)
V
OL
= Sensor Output Low Voltage
I
OUT
= Output Current
T
J
T
A
– θ
JA
V
DD
I
DD
× V
OL
I
OUT
×+()=
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

MCP9502PT-065E/OT

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Description:
Board Mount Temperature Sensors Factory Prog Temp SW Act Hi puch-pull out
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