TC6501/2/3/4
DS21451E-page 6 2002-2012 Microchip Technology Inc.
4.0 DETAILED DESCRIPTION
The TC6501/2/3/4 integrate a temperature sensor with
a factory-programmed threshold switch (see Functional
Block Diagrams in Figure 5-4 through Figure 5-7). A
logic signal is asserted when the die temperature
crosses the factory-programmed threshold. An external
hysteresis input pin allows the user to select either 2°C
or 10°C hysteresis to give further flexibility to the design
of the application. The TC6501 and TC6502 are
intended for a temperature range of 35°C to 125°C in
10°C increments. The TC6501 has an open-drain
output, while the TC6502 has a push-pull output stage.
The TC6503 and TC6504 are intended for a cold
temperature range of -45°C to +15°C in 10°C
increments. The TC6503 has an open-drain output,
while the TC6504 has a push/pull output stage. The
TC6501 and TC6503 are intended for applications with
a microcontroller reset input. The TC6502 and TC6504
are intended for applications where a fan or heater
element is turned on.
Please contact Microchip Technology for the availability
of a particular temperature threshold not included in
Table 4-1.
4.1 Hysteresis Input
To prevent the output from “chattering” at or near the
trip point temperature, a selectable HYST input pin is
provided. Hysteresis can be externally selected at 2°C
(HYST = GND) or 10°C (HYST = V
CC
) by means of the
CMOS compatible HYST input pin. Do not let the HYST
pin float, as this could cause an increase in supply
current. The hysteresis does not depend on the part’s
programmed trip threshold.
TABLE 4-1: FACTORY-PROGRAMMED
THRESHOLD RANGE
4.2 Thermal Considerations
With a 17 µA typical supply current, the TC6501/2/3/4
dissipates very little power. Thus, the die temperature
is basically the same as the package temperature. To
minimize the error in temperature readings, the load
current should be limited to a few milliamps. For
example, the typical thermal resistance of a 5-Pin SOT-
23A package is 140°C/W. If, for instance, the TC6501
had to sink 1 mA, and the output voltage is ensured to
be less than 0.3V, an additional 0.3 mW of power is
dissipated within the temperature sensor. This
corresponds to a 0.042°C rise in die temperature.
Temperature-monitoring accuracy depends on the
thermal resistance between the device being
monitored and the temperature switch die. Heat flows
primarily through the leads onto the die. Pin 2 provides
the lowest thermal resistance to the die. To achieve the
best temperature-monitoring results, the TC6501/2/3/4
should be placed closest to the device being
monitored. Additionally, a short and wide copper trace
from pin 2 to the device should be used. In some cases,
the 5-Pin SOT-23A package can be placed directly
under the socketed microcontroller for improved ther-
mal contact.
Part Number Threshold (T
TH
) Range
TC6501 +35°C < T
TH
< +125°C
TC6502 +35°C < T
TH
< +125°C
TC6503 -45°C < T
TH
< +15°C
TC6504 -45°C < T
TH
< +15°C
