Patent Number: 7,612,585

Title: Pull-up circuit for an input buffer

Abstract: An input buffer has a high voltage leg in parallel with a low voltage leg. The low voltage leg pulls up the pad when the pad voltage is below the power supply voltage. The high voltage leg remains off when the pad voltage is below the power supply. The low voltage leg is turned off when the pad voltage is above the power supply voltage. The high voltage leg is on when the pad voltage is above power supply voltage. A low voltage bias circuit and a high voltage bias circuit protect the transistors in the low and voltage legs when the pad voltage is above the power supply voltage. As a result, the pull-up circuit is high voltage tolerant and does not sink the current from pad.

Inventors: Shah; Pulkit (Bangalore, IN), Kotra; Prasad (Ejipura, IN)

Assignee: Cypress Semiconductor Corporation

International Classification: H03K 19/094 (20060101)

Expiration Date: 1/03/02017