This is a Window Detector circuit. This circuit is used to detect over-voltage or under-voltage. This circuit uses the MAX933 and additional components like resistors. The over-voltage threshold of this circuit is 5.5V and the under-voltage threshold is 4.5V if we use the component values shown. We can choose different threshold by changing the values of R3, R2 and R1. Here is the circuit:
This circuit has hysteresis which is added by R4 and R5 to prevent chatter at the output when the supply voltage is close to a threshold. OUTB and OUTA each provides an active-low over-voltage indication and an active-low under-voltage indication. An active high can be provided by ANDing the two outputs. [Source: MAXIM Application Note]
