AN2504 - Application note

Open Drain Output Advantages

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Open Drain Output Advantages

The advantages of open drain output are the ability to connect more open drain outputs in

parallel (wired OR connections, see Figure 6) as well as connect the output to a power

The hook up on Figure 6 monitors 2 independent supply voltages (3V and 5V). Every time

either the first OR the second supply voltage goes below defined threshold, the input signal

of the MCU, Suspend, goes low.

Figure 6.

Voltage Detectors with Wire OR Connection

A voltage detector with an open drain output can also monitor supply voltages different from

the MCU supply voltage (see Figure 7). The logic high on the MCU Suspend input is

adequate to supply voltage of the MCU.

Figure 7.

Voltage Detector Monitors Different Supply Voltage

AI12906

VCC

VSS

VCC

MCU

STM1061N

OUT

5V

3V

R

VSS

Suspend

VCC

STM1061N

OUT

VSS

AI12907

VSS

VCC

MCU

5V

3V

R

Suspend

VCC

STM1061N

OUT

VSS