TC620HCOA データシートの表示（PDF） - TelCom Semiconductor, Inc

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TC620HCOA

5V, DUAL TRIP POINT TEMPERATURE SENSORS

TelCom Semiconductor, Inc 

5V, DUAL TRIP POINT

TEMPERATURE SENSORS

1

TC620

TC621

DETAILED DESCRIPTION

The TC620/621 consists of a positive temperature coef-

ficient (PTC) temperature sensor, and a dual threshold

detector. Temperature setpoint programming is easily ac-

complished with external programming resistors from the

HIGH SET and LOW SET inputs to VDD. The HIGH LIMIT

and LOW LIMIT outputs remain low as long as measured

temperature is below setpoint values. As measured tem-

perature increases, the LOW LIMIT output is driven high

when temperature equals the LOW SET setpoint (±3°C

max). If temperature continues to climb, the HIGH LIMIT

output is driven high when temperature equals the HIGH

SET setpoint (Figure 1). The CONTROL (hysteresis) output

is latched in its active state at the temperature specified by

the HIGH SET resistor. CONTROL is maintained active until

temperature falls to the value specified by the LOW SET

resistor.

HIGH SET POINT

LOW SET POINT

LOW LIMIT OUTPUT

HIGH LIMIT OUTPUT

CONTROL OUTPUT (COOL OPTION)

CONTROL OUTPUT (HEAT OPTION)

TEMPERATURE

Figure 1: TC620/621 Input vs. Output Logic

Programming The TC620

The resistor values to achieve the desired trip-point

temperatures on HIGH SET and LOW SET are calculated

using EQUATION 1 below:

RTRIP = 0.5997 x T 2.1312

Where: Rtrip = Programming resistor in Ohms

T = The desired trip point temperature

in degrees Kelvin

Equation 1.

For example, a 50°C setting on either the HIGH SET or

LOW SET input is calculated using Equation 1 as follows:

Rset = 0.5997 x ((50 + 273.15)2.1312) = 133.6k Ω

Care must be taken to ensure the LOW SET program-

2 ming resistor is a smaller value than the HIGH SET program-

ming resistor. Failure to do this will result in erroneous

operation of the CONTROL output.

Care must also be taken to ensure the LOW SET

temperature setting is at least 5°C lower than the HIGH SET

temperature setting. That is:

LOW SET ≤ HIGH SET – 5°C

3 The nomograph of Figure 2 can help the user obtain an

estimate of the external resistor values required for the

desired LOW SET and HIGH SET trip points.

250

200

4

150

100

50

-55 -35 -15

5 25 45 65

TEMPERATURE (°C)

85 105 125

Figure 2. TC620 Sense Resistors vs. Trip Temperature

5

Built-in Hysteresis

To prevent output "chattering" when measured tem-

perature is at (or near) the programmed trip point values, the

LOW SET and HIGH SET inputs each have built-in hyster-

esis of – 2°C below the programmed settings (Figure 3).

6

SET POINT

(SET POINT – 2°C)

HIGH LIMIT

7

or LOW LIMIT

Output

Figure 3: Built-in Hysteresis on Low Limit and High Limit Outputs

As shown, the outputs remain in their active state

(hysteresis) until temperature falls an additional 2°C below

the user's setting.

8

TELCOM SEMICONDUCTOR, INC.

2-17

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