DocID15255 Rev 2

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AN2859

Multiplexed diagnostics

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1

Multiplexed diagnostics

1.1

Principle

The multiplexed diagnostic allows the detection of the state of several AC switches

independently using only one MCU input. In this case, an analog/digital converter input

(ADC) of the MCU should be used and must be configured with no pull-up resistor. In this

described (see Figure 2). Note that two output pins of an MCU should be used to control

each STCC08 (IN1 and IN2).

Figure 2. Multiplexed diagnostic schematic of two STCC08

To distinguish the state of each AC switch (ACS1 and ACS2) a divider bridge is used.

each STCC08 (IN1 and IN2), the MCU is able to identify the state of each AC switch by

Note:

STCC08 AVF output and limit the collector current to 5 mA. For further information, and in

AVF

R

IG

AC

IN2

G

MCU

AVF

Load2

Line

Neutral

ACS2

STCC08

2

AVF

GND

AC

IN1

G

AVF

GND

Load1

Line

Neutral

ACS1

R1

R2

R3

R4

STCC08

1

RAC

RAC