AMC23C14 datasheet(32/46 Pages) TI

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8.2.2 Overvoltage and Undervoltage Detection

Industrial I/O modules are frequently powered by external field supplies with a nominal voltage of 24 V and a

tolerance of –15% to +20%. In safety-critical applications, the controller-side may need to know whether the

voltage is in the valid range for correct operation or not. Figure 8-2 shows the AMC23C14 in an application

that monitors a 24-V supply on the high-side and signals undervoltage and overvoltage conditions to the

programmable logic controller (PLC) on the low-side.

The voltage divider R5 and R6 is sized to trip the fixed internal 300-mV threshold when the power supply

exceeds the minimum valid operating voltage of 20.4 V (24 V – 15%). In a second step, R1 (connected to the

REF pin) is sized to trip the adjustable-threshold comparator when the power supply exceeds 28.8 V (24 V +

20%). The AMC23C14 is powered from the field supply and is protected against voltages greater than 30 V by a

Zener diode (Z1) and shunt resistor R4.

When the power supply is below 20.4 V, both outputs of the AMC23C14 are in a Hi-Z state. Between 20.4 V and

28.8 V, OUT1 is in a Hi-Z state and OUT2 is actively pulled low. Both outputs are pulled low, as shown in Figure

8-3, when the power supply is above 28.8 V.

to PLC

Low-side supply (2.7..5.5 V)

3.52 k

VDD1

GND1

REF

AMC23C14

VDD2

OUT2

OUT1

GND2

24 V field supply

100 nF

1 µF

4.17 k

100 nF

1 µF

4.7 k

to PLC

237 k

1 k

27 V

–

1 nF

Figure 8-2. Using the AMC23C14 for Overvoltage and Undervoltage Detection

Supply

Voltage

OUT2

28.8 V

20.5 V

28.5 V

OUT1

20.8 V

Undervoltage

Normal

Overvoltage

Undervoltage

Off

Normal

Off

Valid Supply Range

Figure 8-3. Output of the AMC23C14 in Supply Voltage Supervisor Application

AMC23C14

SBAS945A – FEBRUARY 2022 – REVISED JULY 2022

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