MCP9509C MICROCHIP [Microchip Technology], MCP9509C Datasheet - Page 16

• Manufacturer Part Number: MCP9509C
• Description: Resistor-Programmable Temperature Switches
• Manufacturer: MICROCHIP [Microchip Technology]

MCP9509/10
4.6
The MCP9509/10 temperature switch integrates a
temperature sensor and a comparator circuit which out-
puts an alert signal when the user programmed tem-
perature threshold is exceeded. The external resistor
value to set the output threshold can be determined
using
(typical) biases the external resistor R
diode is used to measure ambient temperature. When
the voltage across the thermal diode exceeds the volt-
age across R
sensor output de-asserts when the diode voltage drops
below V
The MCP9509/10 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 MCP9509 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
powered with 3V
level-shifted by connecting 3V
as shown in
need for an external resistor while providing wired-Or
function
push-pull output configuration for a direct connection to
the processor with Active-Low or Active-High assert
polarities.
FIGURE 4-5:
Configuration with Level-shift.
DS22114A-page 16
R
R
SET
SET
Table
HYST
HYST
SET
SET
SET
Application Information
(Figure
4-2. A constant current source I
and the user selected hysteresis level.
Figure
SET
MCP9509
MCP9509
5V
5V
, V
DD
4-6). The MCP9510 also provides
DD
DD
DD
SET
4-5. The MCP9510 elliminates the
and the controller or processor is
, the external resistor can be
, the sensor output asserts. The
MCP9509 Wired-Or Output
OUT
OUT
DD
to the pull-up resistor
3V
I/O
DD
R
SET
PULL_UP
. A thermal
Micro-
controller
SET
3V
= 5 µA
DD
FIGURE 4-6:
Configuration with Internal Pull-up Resistor.
4.6.1
This family of sensors measure temperature by moni-
toring 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. It is also
recommended to use a de-coupling capacitor of 0.1 µF
to 1 µF between V
When connecting an external resistor to the MCP9509
device, the current through the pull-up resistor must be
considered to prevent self-heat due to power. This can
be determined using
EQUATION 4-3:
Where:
R
R
SET
SET
HYST
HYST
I
SET
SET
T
V
OUT
θ
J
T
OL
T
JA
–
A
J
LAYOUT CONSIDERATION AND
THERMAL CONSIDERATION
T
A
MCP9510
MCP9510
5V
5V
=
=
=
=
=
=
DD
θ
DD
DD
JA
OUTSET
OUTSET
Equation
(
and GND pins for stability.
V
Junction Temperature
Ambient Temperature
Package Thermal Resistance
(220.7 °C/W)
Sensor Output Low Voltage
Output Current
MCP9510 Wired-Or Output
EFFECT OF
SELF-HEATING
DD
© 2008 Microchip Technology Inc.
OUT
OUT
×
I
DD
4-3.
+
V
OL
I/O
×
I
OUT
Micro-
controller
5V
)
DD