Electrostatic protection circuit

A protection circuit connected between a power source and a protected internal circuit, the protection circuit comprising:

• a clamp circuit connected between a first power source line at a first power source potential and a first connection node, the clamp circuit having a response to a voltage difference between the first power source line and the first connection node such that an electric current passing through the clamp circuit varies non-linearly upon reaching a threshold voltage;
• a trigger circuit connected between the first connection node and a second power source line at a second power source potential, the trigger circuit configured to output a trigger signal from a trigger output node in response to the electric current passing through the clamp circuit;
• a buffer circuit having a buffer input node connected to the trigger output node, the buffer circuit biased by a voltage difference between a potential at the first connection node and the second power source potential, and configured to output a drive signal from a buffer output node in response to the trigger signal;
• and
• a switch circuit configured to electrically connect the first power source line to the second power source line in response to the drive signal.

An electrostatic protection circuit, comprising:

• a first diode connected between a first power source line and a first connection node, the first diode having a response to a voltage difference between the first power source line and the first connection node such that an electric current passing through the first diode varies non-linearly upon reaching a threshold voltage;
• a trigger circuit connected between the first connection node and a second power source line, the trigger circuit configured to output a trigger signal in response to the electric current passing through the first diode;
• a buffer circuit that is biased by a voltage between the first connection node and the second power source line, and configured to output a drive signal in response to the trigger signal;
• and
• a switch circuit having a main current path connected between the first power source line and the second power source line, the switch circuit configured to switch the conduction state of the main current path between on and off in response to the drive signal