High-voltage cmos level shifter

Abstract

A high-voltage level shifter includes one or more complementary NMOS/PMOS series intermediate transistor pairs to divide the high-voltage supply range into two or more sub-ranges. The level shifter has a differential structure with complementary NMOS input transistors. Cross-coupled PMOS output transistors provide complementary outputs. The complementary NMOS/PMOS series intermediate transistor pairs separate the NMOS input transistor drains from the PMOS output transistor drains. In order to divide the high voltage range into h subranges, h-1 complementary NMOS/PMOS series intermediate transistor pairs are used each being biased by monotonically increasing fixed intermediate voltages. In a shared-bias embodiment, each complementary NMOS/PMOS series intermediate transistor pair is biased by a single corresponding intermediate voltage. In a split-bias embodiment, each complementary NMOS/PMOS series intermediate transistor pair is biased by a corresponding NMOS bias voltage and a corresponding PMOS bias voltage, in which the NMOS bias voltage is higher than the PMOS bias voltage by the sum or the NMOS threshold voltage and the PMOS threshold voltage. In another aspect, the N-wells of the PMOS transistors are tied to an upwardly vertically adjacent intermediate voltage in the shared-bias embodiments, and are tied to an upwardly vertically adjacent NMOS bias voltage in the split-bias embodiments. In a twin tub embodiment for very high voltage applications, the P-wells of the NMOS transistors are tied to a downwardly vertically adjacent intermediate voltage in the shared-bias embodiments, and are tied to a downwardly vertically adjacent PMOS bias voltage for the split-bias embodiments.