Power-on/power-down output tri-state control circuit for CMOS device power supply

Abstract

The invention discloses a power-on / power-down output tri-state control circuit for a CMOS device power supply. The tri-state control circuit comprises an MOS tube series resistance voltage-division circuit, a PMOS switching tube, and a shaping filtering circuit. According to the shaping filtering circuit, a PMOS transistor being equivalent to a capacitor is coupled to a grid terminal and a power supply terminal of the PMOS switching tube; an NMOS transistor being equivalent to a capacitor is coupled to a drain terminal and the power supply terminal of the PMOS switching tube; and a buffer circuit is connected to the drain terminal and a control circuit output terminal of the PMOS switching tube. According to the invention, when the power-on value or the power-down value of the power supply of the device is lower than the set threshold level, the device output port is controlled to be in a high impedance state, thereby maintaining accuracy of signal transmission at the device output bus and protecting the device from being damaged; and when the power-on value or the power-down value of the power supply of the device is higher than the set threshold level, the control circuit returns the control to the controlled device output port and thus the device can output an enabling signal OE to control three states of the output port.

Description

technical field [0001] The invention relates to a three-state control circuit for outputting power on and off of a CMOS device power supply, in particular to a circuit structure for controlling the output port of a device to maintain a high-impedance state when the device power supply is powered on or off and is lower than a set threshold level value. It belongs to the field of device control. Background technique [0002] With the rapid development of the integrated circuit industry and the increasingly complex and changeable application environment, the requirement to ensure the integrity of bus transmission signals becomes more and more important. The live plugging and unplugging of single boards is an important application function in communication equipment. In order to realize the live plugging and unplugging of single boards, corresponding interface devices need to meet certain characteristics. In the normal power supply mode of the traditional interface device, the ...

AI Technical Summary

Problems solved by technology

However, if the power supply is abnormally powered, especially during the power-on or power-off process, traditional interface devices often cannot normally control the output terminal to work in a high-impedance state, which may easily lead to error reversal during signal transmission on the bus. Even the damage of the interface device

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