Semiconductor integrated circuit

Abstract

An N-channel transistor is provided as a switch between a high potential power line and a low potential power line. A high-pass filter is constituted by a capacitor and a resistor. When a voltage between the high potential power line and the low potential power line is started to oscillate by a switching operation, the high-pass filter causes a high-pass component thereof to pass, thereby turning ON the N-channel transistor to reduce a ringing.

1 . A semiconductor integrated circuit comprising: 
 a switch provided between a high potential power line and a low potential power line; and    a high-pass filter that causes a high-pass component of a voltage generated between the high potential power line and the low potential power line to pass and outputs the high-pass component as a signal to turn on the switch.    
   
   
       2 . The semiconductor integrated circuit according to  claim 1 , wherein the switch includes a field effect transistor having a drain connected to one of the high potential power line and the low potential power line, a source connected to the other, and a gate to which a signal output from the high-pass filter is given.  
   
   
       3 . The semiconductor integrated circuit according to  claim 2 , wherein the field effect transistor serves as an electrostatic breakdown protecting device.  
   
   
       4 . A ringing reduction circuit provided inside a semiconductor integrated circuit that includes an output buffer circuit and an output signal line for transmitting an output signal of the output buffer to a load outside the semiconductor integrated circuit, the ringing reduction circuit comprising: 
 a switching element inserted between the output signal line and a high-potential power line or a low-potential power line for supplying a power supply voltage to the output buffer circuit; and    a ringing detector that outputs a signal for turning on the switching element when ringing occurs in the output signal and the output signal exceeds a reference level in a positive or negative direction.    
   
   
       5 . The ringing reduction circuit according to  claim 4 , wherein the ringing detector comprises a comparator for detecting that the output signal exceeds the reference level in the positive or negative direction by comparing a level of the output signal line with a level of the high-potential power line or the low-potential power line.  
   
   
       6 . The ringing reduction circuit according to  claim 4 , wherein the ringing detector comprises a comparator for detecting that the output signal exceeds the reference level in the positive or negative direction by comparing a level of the output signal line with a level of a power line that is different from the high-potential power line and the low-potential power line.  
   
   
       7 . The ringing reduction circuit according to  claim 4 , wherein the ringing detector comprises a comparator for detecting that the output signal exceeds the reference level in the positive or negative direction by comparing a level of the high-potential power line or the low-potential power line with a level of a power line that is different from the high-potential power line and the low-potential power line and is not part of a path of a switching current flowing through the output buffer circuit.  
   
   
       8 . The ringing reduction circuit according to  claim 4 , wherein 
 the switching element is inserted between the output signal line and the low-potential power line, and    the ringing detector outputs a signal for turning on the switching element when detecting that the output signal exceeds, in the positive direction, the reference level that is a level of the high-potential power line or a level that is more stable than the level of the high-potential power line.    
   
   
       9 . The ringing reduction circuit according to  claim 4 , wherein 
 the switching element is inserted between the output signal line and the high-potential power line, and    the ringing detector outputs a signal for turning on the switching element when detecting that the output signal exceeds, in the negative direction, the reference level that is a level of the low-potential power line or a level that is more stable than the level of the low-potential power line.    
   
   
       10 . The ringing reduction circuit according to  claim 4 , wherein 
 the switching element comprises a first switching element inserted between the output signal line and the low-potential power line and a second switching element inserted between the output signal line and the high-potential power line; and    the ringing detector comprises a first comparator for outputting a signal for turning on the first switching element when detecting that the output signal exceeds, in the positive direction, a first reference level that is a level of the high-potential power line or a level that is more stable than the level of the high-potential power line and a second comparator for outputting a signal for turning on the second switching element when detecting that the output signal exceeds, in the negative direction, a second reference level that is a level of the low-potential power line or a level that is more stable than the level of the low-potential power line.    
   
   
       11 . (canceled)