AN2846 datasheet(6/35 Pages) STMICROELECTRONICS

6 / 35 page

Application guidelines

AN2846

6/35

Doc ID 15130 Rev 1

Figure 3.

Limited current versus junction temperature

Figure 4 shows the ILIM trend versus RREF. according to the input current setting and

therefore the dissipated power, the SCLT3-8 should be cooled with a sufficient copper heat

sink area (see Section 2)

Figure 4.

Typical limiting input current versus RREF

1.2.2

Input characteristics (IEC 61131-2 standard)

According to the IEC 61131-2 standard and referring to type 3, when the input current is less

than 1.5 mA the output circuit passes all the input current, keeping the monitoring LED off

and transmits a low level state to the input state register.

When the module input voltage VI, taking into account the 2.2 kΩ input resistor, is higher

than 11 V (that is, the SCLT3-8 input voltage VIN is higher than 5 V) the monitoring LED is

on and the circuit transmits a high level state to the input state register.

Figure 5 gives the input characteristics and operating regions of type 3, defined in the

IEC 61131-2 standard, and the typical SCLT3-8 input characteristic.

Vcc = 24 V, Vi = 11 V

2.1

2.2

2.3

2.4

2.5

2.6

-25 °C

25°C

125°C

150°C

(mA)

lim

Junction temp (°C)

IN1

IN2

IN3

IN4

IN5

IN6

IN7

IN8

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.1

3.9

(mA)

lim

Test conditions:

versus R

= 24 V, V = 24 V

LIM

REF

(k)

REF

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