TC6502(2004) Просмотр технического описания (PDF) - Microchip Technology

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TC6502
(Rev.:2004)

Ultra Small Temperature Switches with Pin Selectable Hysteresis

Microchip Technology 

TC6501/2/3/4

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 availabil-

ity 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 = VCC) 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

Part Number

TC6501

TC6502

TC6503

TC6504

Threshold (TTH) Range

+35°C < TTH < +125°C

+35°C < TTH < +125°C

-45°C < TTH < +15°C

-45°C < TTH < +15°C

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.

DS21451D-page 6

 2004 Microchip Technology Inc.

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