Microchip Technology APGRD004 Data Sheet
www.microchip.com/lighting
LED Lighting Solutions Design Guide
17
LED Lighting Solutions
Logic Output Temperature Sensors
Low cost temperature
sensing devices such
as the TC6501 and
TC6502 (offered in
SOT-23 packages) can be
conveniently placed near
power LED(s) to obtain a
more accurate temperature
monitoring and provide a
logic output fault signal.
sensing devices such
as the TC6501 and
TC6502 (offered in
SOT-23 packages) can be
conveniently placed near
power LED(s) to obtain a
more accurate temperature
monitoring and provide a
logic output fault signal.
The fault signal will be activated as soon as a factory-
programmed temperature threshold is reached. Temperature
threshold values can be selected in increments of 20°C as
indicated in the following table.
programmed temperature threshold is reached. Temperature
threshold values can be selected in increments of 20°C as
indicated in the following table.
TC6501/TC6502 Logic Output Temperature Sensors
Device
Temperature
Threshold (°C)
TC6501P045VCT
45
TC6501P065VCT
65
TC6501P075VCT
75
TC6501P095VCT
95
TC6501P0105VCT
105
TC6501P0115VCT
115
TC6501P0120VCT
120
TC6501P0125VCT
125
Resistor-Programmable Temperature Switches
The MCP9509/10 devices are programmable logic output
temperature switches. The temperature switch threshold can
be programmed with a single external resistor, which provides
high design flexibility and simplicity. In addition, this family
of devices provide user programmable features such as 2°C
and 10°C (typical) switch hysteresis and output structure
configuration. The MCP9509 provides an open drain output,
whereas the MCP9510 is offered in three different user
selectable output configurations: Active-low/Active-high
push pull and Active-Low Open-Drain output with an internal
100 kΩ pull-up resistor.
temperature switches. The temperature switch threshold can
be programmed with a single external resistor, which provides
high design flexibility and simplicity. In addition, this family
of devices provide user programmable features such as 2°C
and 10°C (typical) switch hysteresis and output structure
configuration. The MCP9509 provides an open drain output,
whereas the MCP9510 is offered in three different user
selectable output configurations: Active-low/Active-high
push pull and Active-Low Open-Drain output with an internal
100 kΩ pull-up resistor.
The MCP9509/10 operate from 2.7V to 5.5V. This family is
capable of triggering for temperatures -40°C to +125°C with
high accuracy.
capable of triggering for temperatures -40°C to +125°C with
high accuracy.
MCP9509/10 Resistor-Programmable
Temperature Switches
Temperature Switches
Device
Temperature Threshold (°C)
MCP9509CT-E/OT
-40ºC to +125ºC (Falling Hot to Cold)
MCP9509HT-E/OT
-40ºC to +125ºC (Rising Cold to Hot)
MCP9510CT-E/CH
-40ºC to +125ºC (Falling Hot to Cold)
MCP9510HT-E/CH
-40ºC to +125ºC (Rising Cold to Hot)
T
OVER
T
OVER
TC6501
TC6502
GND
V
CC
HYST
GND
TC6501
TC6502
TC6502
Temperature Sensing Solutions for
Power LED Applications
Power LED Applications
Every light source has a specific energy efficiency. A certain
portion of the energy supplied to it is wasted in the form of
heat. One of the fundamental differences between Power
LED technology and other traditional sources of light is in
the way this heat is transferred. In fact, LEDs are particularly
good at producing a radiation with very narrow range of
frequencies typically designed to produce a specific color
in the visible spectrum. There is very little infrared (heat)
radiation produced. All the heat produced by the light
source has to be transferred instead by contact. Packaging
technology plays an important role in facilitating the heat
transfer from the LED, but an accurate thermal analysis
of the entire lighting application (total thermal resistance
from junction to ambient) is required to guarantee that
the maximum temperature of the junction is not exceeded
during operation. In particular, white LEDs employ phosphor
materials to convert the monochromatic light emitted into a
wider spectrum, to produce a “white” color. The phosphors
are even more sensitive to temperature and can be easily
damaged if overheated.
portion of the energy supplied to it is wasted in the form of
heat. One of the fundamental differences between Power
LED technology and other traditional sources of light is in
the way this heat is transferred. In fact, LEDs are particularly
good at producing a radiation with very narrow range of
frequencies typically designed to produce a specific color
in the visible spectrum. There is very little infrared (heat)
radiation produced. All the heat produced by the light
source has to be transferred instead by contact. Packaging
technology plays an important role in facilitating the heat
transfer from the LED, but an accurate thermal analysis
of the entire lighting application (total thermal resistance
from junction to ambient) is required to guarantee that
the maximum temperature of the junction is not exceeded
during operation. In particular, white LEDs employ phosphor
materials to convert the monochromatic light emitted into a
wider spectrum, to produce a “white” color. The phosphors
are even more sensitive to temperature and can be easily
damaged if overheated.
Before the LED junction reaches the maximum operating
junction temperature (typically 125°C) the temperature
increase will have negative impact on a number of LED
characteristics including efficiency, light intensity, lifetime
and color.
junction temperature (typically 125°C) the temperature
increase will have negative impact on a number of LED
characteristics including efficiency, light intensity, lifetime
and color.
While the safe way to design a power LED application is to
provide a low temperature resistance path to a heat sink
that is dimensioned for the worst possible environmental
and usage conditions, this might not always be possible
for physical or cost constraints. For this reason driver
ICs used in LED applications (such as the MCP1630 and
MCP1650) often incorporate an over-temperature protection,
performing what is substantially a device shutdown when
the temperature rises above a given threshold. While this is
effective to protect the device from reaching temperatures
that could damage the LED (or the phosphor layer for white
LED applications), the driver IC is not always guaranteed
to be placed close to the emitting device(s). If the LEDs
are arranged in modules, separate from the driving circuit,
comprising several emitters connected in series or parallel,
the temperature sensed by the driver could be considerably
different from the actual module emitter’s junctions.
provide a low temperature resistance path to a heat sink
that is dimensioned for the worst possible environmental
and usage conditions, this might not always be possible
for physical or cost constraints. For this reason driver
ICs used in LED applications (such as the MCP1630 and
MCP1650) often incorporate an over-temperature protection,
performing what is substantially a device shutdown when
the temperature rises above a given threshold. While this is
effective to protect the device from reaching temperatures
that could damage the LED (or the phosphor layer for white
LED applications), the driver IC is not always guaranteed
to be placed close to the emitting device(s). If the LEDs
are arranged in modules, separate from the driving circuit,
comprising several emitters connected in series or parallel,
the temperature sensed by the driver could be considerably
different from the actual module emitter’s junctions.