Ping pong comparator voltage monitoring circuit

摘要

A ping pong comparator voltage monitoring circuit which includes first and second comparators having inputs connected to a voltage Vin to be monitored, and second inputs connected to first and second nodes, respectively. A multiplexer alternately couples the first and second comparator outputs to an output in response to a periodic control signal. A ground-referenced voltage Vref1 is provided at a third node and a voltage Vref2 referenced to Vref1 is at a fourth node. A hysteresis hyst1 is switchably connected between the third and first nodes, and a hysteresis hyst2 is switchably connected between the fourth and second nodes. Hyst1 and hyst2 are switched in when the mux output toggles due to a rising Vin, and are switched out when the mux output toggles due to a falling Vin.

主权项

1. A ping pong comparator voltage monitoring circuit, comprising:
a first comparator having a first input connected to a voltage Vin to be monitored, a second input connected to a first node, and an output which toggles from a first state to a second state when Vin increases above the voltage applied to said first comparator's second input and toggles from said second state to said first state when Vin falls below the voltage applied to said first comparator's second input; a second comparator having a first input connected to said voltage Vin, a second input connected to a second node, and an output which toggles from a first state to a second state when Vin increases above the voltage applied to said second comparator's second input and toggles from said second state to said first state when Vin falls below the voltage applied to said second comparator's second input; a multiplexer connected to receive the outputs of said first and second comparators at first and second inputs, respectively, and to receive a periodic control signal at a ‘select’ input, said multiplexer arranged to alternately couple the voltage applied to said first and second inputs to an output in response to said periodic control signal, said multiplexer output being the output of said voltage monitoring circuit; a first reference voltage source which produces a voltage Vref1 at a third node which is referenced to a circuit common point; a second reference voltage source which produces a voltage Vref2 at a fourth node which is referenced to said voltage Vref1 such that the voltage at said fourth node is given by Vref1+Vref2; a first hysteresis voltage source which produces a voltage hyst1 and is arranged to be switchably connected between said third node and said first node; and a second hysteresis voltage source which produces a voltage hyst2 and is arranged to be switchably connected between said fourth node and said second node; said voltage monitoring circuit arranged such that said first and second hysteresis voltage sources are switched in such that the voltage at said first node is Vref1+hyst1 and the voltage at said second node is Vref1+Vref2+hyst2 when said multiplexer output has toggled from said first state to said second state due to a rising value of Vin, and such that the voltage at said first node is Vref1 and the voltage at said second node is Vref1+Vref2 when said multiplexer output has toggled from said second state to said first state due to a falling value of Vin.