Power-up signal generation circuit

Abstract

A power-up signal generation circuit includes a fixed level transition voltage generation unit, a variable level transition voltage generation unit, a comparison unit, and a selective output unit. The fixed level transition voltage generation unit is configured to generate a fixed level transition voltage changing at a constant level of an external voltage. The variable level transition voltage generation unit is configured to generate a variable level transition voltage changing at a level of an external voltage which varies depending on temperature. The comparison unit is configured to compare the level of the fixed level transition voltage with the level of the variable level transition voltage, and generate a selection signal. The selective output unit is configured to output the fixed level transition voltage or the variable level transition voltage as a power-up signal in response to the selection signal.

What is claimed is: 
     
         1 . A power-up signal generation circuit comprising:
 a fixed level transition voltage generation unit configured to generate a fixed level transition voltage at a level of an external voltage;   a comparison unit configured to compare the level of the fixed level transition voltage with the level of a variable level transition voltage and generate a selection signal; and   a selective output unit configured to output the fixed level transition voltage or the variable level transition voltage as the power-up signal in response to the selection signal.   
     
     
         2 . The power-up signal generation circuit of  claim 1 , wherein the fixed level transition voltage generation unit comprises:
 a first voltage generation section configured to generate a first voltage whose peak voltage is lowered as temperature increases; and   a second voltage generation section configured to generate a second voltage changing with reference to the peak voltage of the first voltage.   
     
     
         3 . The power-up signal generation circuit of  claim 2 , wherein the first voltage generation section comprises:
 a first resistor coupled between an external voltage terminal and a first node through which the first voltage is outputted; and   a first pull-down element coupled between the first node and a ground voltage terminal, and configured to pull down the first node in response to the external voltage.   
     
     
         4 . The power-up signal generation circuit of  claim 3 , wherein the second voltage generation section comprises:
 a MOS transistor coupled between the external voltage terminal and a second node, and configured to operate as a resistor;   a second resistor coupled between the second node and a third node through which the second voltage is outputted; and   a second pull-down element coupled between the third node and the ground voltage terminal, and configured to pull down the third node in response to the first voltage.   
     
     
         5 . The power-up signal generation circuit of  claim 2 , wherein the fixed level transition voltage generation unit further comprises a buffer section configured to buffer the second voltage and generate the fixed level transition voltage. 
     
     
         6 . The power-up signal generation circuit of  claim 1 , wherein the comparison unit is configured to generate the selection signal of a first level when the level of the fixed level transition voltage is higher than the level of the variable level transition voltage, and generate the selection signal of a second level when the level of the fixed level transition voltage is lower than the level of the variable level transition voltage. 
     
     
         7 . The power-up signal generation circuit of  claim 6 , wherein the selective output unit is configured to output the variable level transition voltage as the power-up signal when the selection signal is at the first level, and output the fixed level transition voltage as the power-up signal when the selection signal is at the second level. 
     
     
         8 . A power-up signal generation circuit comprising:
 a variable level transition voltage generation unit configured to generate a variable level transition voltage at levels of the external voltage depending on the temperature;   a comparison unit configured to compare the level of a fixed level transition voltage with the level of the variable level transition voltage and generate a selection signal; and   a selective output unit configured to output the fixed level transition voltage or the variable level transition voltage as the power-up signal in response to the selection signal.   
     
     
         9 . The power-up signal generation circuit of  claim 8 , wherein the variable level transition voltage generation unit comprises:
 a voltage division section configured to divide the external voltage and generate a division voltage.   
     
     
         10 . The power-up signal generation circuit of  claim 9 , wherein the voltage division section comprises:
 a first resistor coupled between an external voltage terminal and a second node through which the division voltage is outputted; and   a second resistor coupled between the second node and a ground voltage terminal.   
     
     
         11 . The power-up signal generation circuit of  claim 10 , wherein the variable level transition voltage generation unit comprises:
 a first MOS transistor coupled between a first node and the ground voltage terminal, and configured to pull down the first node in response to the division voltage; and   a second MOS transistor coupled between the external voltage and the first node, and configured to operate as a resistor.   
     
     
         12 . The power-up signal generation circuit of  claim 8 , wherein the variable level transition voltage generation unit further comprises a buffer section configured to buffer a signal of the first node and generate the variable level transition voltage.