High voltage low current enable pin startup circuit

An enable circuit, comprising:

• an enable terminal configured to receive an enable signal at a first voltage level;
• an input terminal configured to receive a supply voltage;
• a clamp configured to receive the supply voltage and generate a start voltage by clamping the supply voltage to a threshold voltage level that is less than the supply voltage;
• and
• a first switch coupled to the enable terminal, the first switch configured to be closed by the start voltage,
• wherein the enable signal is configured to pass through the first switch when the first switch is closed to generate an enable intermediate signal at a second voltage level, the second voltage level limited by the start voltage.

A method for generating a voltage rail for an integrated circuit, comprising:

• receiving a supply voltage and an enable signal at a first voltage level, the first voltage level corresponding to the supply voltage;
• clamping the supply voltage to a threshold voltage level that is less than the supply voltage to generate a start voltage;
• passing the enable signal through a first switch to generate an enable intermediate signal at a second voltage level that is less than the first voltage level;
• limiting the second voltage level with the start voltage;
• in response to the enable intermediate signal being generated at the second voltage level, generating a start signal;
• and
• in response to the start signal being generated, generating an output signal at a third voltage level that is less than the first voltage level.