Two-way IO circuit for preventing current from flowing backwards

Abstract

The invention discloses a two-way IO circuit for preventing a current from flowing backwards. The circuit comprises a two-way IO module, a substrate voltage bias module and a gate voltage bias module. The substrate voltage bias module is connected with the two-way IO module and is used for controlling the on-off condition of a PMOS transistor in the two-way IO module through an output signal. The gate voltage bias module is connected with the two-way IO module and the substrate voltage bias module and is used for controlling the on-off condition of the PMOS transistor in the two-way IO module and the on-off condition of the PMOS transistor in the substrate voltage bias module through the output signal. According to the method, the current can be prevented from flowing backwards.

Description

technical field [0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a bidirectional IO circuit for preventing current backflow. Background technique [0002] With the vigorous development of integrated circuit technology, electronic products are more and more closely related to work and life. As the core module of controlling various components in electronic products, single-chip microcomputers often need to communicate with chip ports of different power supply voltages. [0003] The existing IO output circuit is usually as figure 1 Shown by the solid line. When this IO is in input mode, the internal control signal will V A set high (that is, V DD ), the V B The purpose of setting low is to turn off the PMOS and NMOS to prevent the transistor from being turned on and forming a reverse current. Since the source, substrate, and gate of the PMOS transistor are all V DD , then this PMOS tube can be equivalent to a diode,...

AI Technical Summary

Problems solved by technology

[0005] However when the circuit is in high voltage input mode, V OUT voltage greater than V DD , at this time the positive phase terminal voltage V of the equivalent diode OUT greater than the inverting terminal voltage V DD , when V OUT the voltage ratio V DD When the conduction voltage of a forward-biased diode (usually 0.7V) is exceeded, the equivalent diode conducts, and the current will flow from the input terminal V OUT Flow through the PMOS, and finally flow back to the power supply voltage V of the chip DD On the other hand, if the size of the PMOS is too large, it may cause the chip to heat up due to excessive current, or even burn out.

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