Voltage detection circuit applied to fast power off

Abstract

The invention discloses a voltage detection circuit applied to quick disconnection of a power source. The voltage detection circuit applied to quick disconnection of the power source comprises a voltage division circuit, a voltage protection circuit and a comparator. The voltage diversion circuit comprises two resistors connected in series. Two capacitors are connected with the two resistors in parallel. The impedance ratio of the two capacitors is equal to the impedance ratio of the two resistors. The voltage protection circuit comprises a first NMOS transistor and a transistor series-connection structure. In the quick disconnection process of the external power source, voltage of the external power source can be divided through the two capacitors, division voltage of voltage division nodes drops quickly along with the external power source and is compared with reference voltage, the comparator turns over quickly, and accordingly quick response of the voltage detection circuit is achieved.

Description

technical field [0001] The present invention relates to a semiconductor integrated circuit, in particular to a voltage detection circuit (VD) applied to power off quickly. Background technique [0002] Such as figure 1 Shown is a schematic structural diagram of an existing voltage detection circuit; the existing voltage detection circuit includes: a voltage divider circuit, a voltage protection circuit, and a comparator CMP1. [0003] The voltage divider circuit is used to divide the external voltage source vext and output the divided voltage. The voltage divider circuit is composed of resistors 101 and 102 connected in series. output. [0004] The voltage protection circuit includes an NMOS transistor Mn101 and a series connection structure of transistors. [0005] The operating voltage range of the NMOS transistor Mn101 is greater than the variation range of the external voltage source vext, the gate of the NMOS transistor Mn101 is connected to the internal voltage sour...

AI Technical Summary

Problems solved by technology

[0007] In the prior art, in order to improve the response speed of the voltage detection circuit, it can be realized by increasing the response speed of the comparator, but because the circuit usually has power consumption requirements, the resistors R101 and R102 will be very large, so the external voltage source vext When powering off quickly, such as tens of nanoseconds, the low-level maintenance time after power-off is also in nanoseconds, and the voltage dividing node Vd_net is too late to respond quickly, so that the voltage detection circuit cannot respond to the power supply voltage. Therefore, the existing voltage detection circuit cannot be applied when the power is quickly turned off

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