Loss of signal detection circuit

A circuit, comprising:

• a first differential comparator having a first input coupled to a first node, a second input coupled to a second node, and an output coupled to a third node;
• a second differential comparator having a first input coupled to the second node, a second input coupled to the first node, and an output coupled to a fourth node;
• a first inverter coupled between the third node and a fifth node;
• a second inverter coupled between the fourth node and a sixth node;
• a first logic circuit having a first input coupled to the fifth node, a second input coupled to the sixth node, and an output;
• a second logic circuit having a first input coupled to the third node, a second input coupled to the fourth node, and an output;
• a resistor coupled between the output of the second logic circuit and a seventh node;
• a capacitor coupled between the seventh node and a ground node;
• and
• a first positive feedback circuit coupled between the third node and the fourth node and having a control input coupled to the seventh node.

A circuit, comprising:

• a first inverter coupled between a first node and a second node;
• a second inverter coupled between a third node and a fourth node;
• a first logic circuit having a first input coupled to the second node, a second input coupled to the fourth node, and an output;
• and
• a first positive feedback circuit coupled between the first node and the third node and having a control input, the first positive feedback circuit comprising:
• a first switch coupled between the first node and a fifth node, the first switch having a control input;
• a second switch coupled between the third node and a sixth node, the second switch having a control input;
• a third inverter having an input coupled to the sixth node and an output coupled to the fifth node;
• and
• a fourth inverter having an input coupled to the fifth node and an output coupled to the sixth node.