ASM690A/692A, ASM802L/802M, ASM805L

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Figure 9. Hysteresis Added to PFI Pin

Monitoring Capabilities of the Power−fail Input:

Although designed for power supply failure monitoring,

the PFI pin can be used for monitoring any voltage condition

that can be scaled by means of a resistive divider. An

example is the negative power supply monitor configured in

Figure 10. In this case a good negative supply will hold the

PFI pin below 1.25 V and the PFO pin will be at logic “0”.

As the negative voltage declines, the voltage at the PFI pin

will rise until it exceeds 1.25 V and the PFO pin will go to

logic “1”.

Figure 10. Using PFI to Monitor Negative Supply

Voltage