Schmitt trigger

Abstract

The invention discloses a Schmitt trigger, and relates to the technical field of integrated circuits. The flip-flop comprises a first-stage sub-circuit, a second-stage sub-circuit and an inverter sub-circuit; the first-stage sub-circuit is connected to a signal input end and outputs a first-stage output voltage to the second-stage sub-circuit, the second-stage sub-circuit outputs a second-stage output voltage to the inverter sub-circuit, and the inverter sub-circuit inverts the second-stage output voltage and then outputs the second-stage output voltage through a signal output end; the second-stage sub-circuit comprises a tenth field effect transistor and a first current source, the tenth field effect transistor is connected to low power supply voltage, a second field effect transistor and a sixth field effect transistor, and the first current source is connected to the tenth field effect transistor and the phase inverter sub-circuit. According to the technical scheme of the invention, the problem of compatibility with an old-version interface protocol when a new-version interface circuit is designed by using an advanced manufacturing process can be solved, so that the circuit cost is reduced.

Description

technical field [0001] The invention relates to the technical field of integrated circuits, in particular to a Schmitt trigger. Background technique [0002] A Schmitt trigger is an inverter with hysteresis. Different from ordinary inverters, the Schmitt trigger has two threshold voltages, which are positive threshold voltage and negative threshold voltage. When the input signal rises from low level to high level, the output circuit The input voltage corresponding to the state change of the circuit is called the positive threshold voltage, and the input voltage corresponding to the output circuit state change is called the negative threshold voltage in the process of the input signal falling from high level to low level. This characteristic makes the Schmitt trigger widely used in circuits with anti-noise shaping. The voltage difference between the positive and negative threshold voltages is called the firing window of the Schmitt trigger. [0003] Traditional Schmitt tri...

AI Technical Summary

Problems solved by technology

However, in the process of continuous updating of the USB interface protocol, the speed supported continues to increase, which requires the use of a more advanced process technology. Under the advanced process technology, due to cost, MOS tube working speed and power consumption, etc. Considering that you may not choose a 3.3V MOS tube, but only choose a 1.8V MOS tube, but the new version of the USB interface protocol generally requires backward compatibility with the old version of the interface protocol. MOS tube to deal with the problem of 3.3V voltage and data signal

If you put directly figure 1 The 8 MOS tubes in the circuit are replaced by MOS tubes with a withstand voltage of 3.3V to MOS tubes with a withstand voltage of 1.8V. Since the power and data signals are still 3.3V, the circuit is easily broken down and damaged

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