Interface system between controller IC and driver IC, and IC suitable for such interface system

Abstract

A disk controller IC ( 11 ), driven by a first supply voltage (V 1 ), is provided with a push-pull type output circuit having an output terminal (P 1 ). The output circuit may be turned ON/OFF by a control signal. On the other hand, disk driver IC ( 12 ) is provided with a first voltage and a series of a pull-up resistor (R 1 ) and a diode (D 3 ) connected in series between an input terminal and the first supply voltage. An interface is established for the ICs ( 11, 12 ) by connecting the output terminal (P 1 ) and the input terminal (P 2 ) together.

1 - 20 . (canceled)  
   
   
       21 . An interface system for interfacing two circuits, comprising 
 a first circuit having    a push-pull type output circuit coupled between a first power supply voltage and the ground, said push pull type output circuit controlled to be ON or OFF by a control signal, and    an output terminal for outputting an output signal of said said first circuit; and    a second circuit having    an input terminal connected to said output terminal of said first circuit for receiving said output signal of said first circuit as the input signal to said second circuit,    an internal circuit having a second power supply voltage higher than said first power supply voltage as an operating voltage,    a terminal for supplying said first power supply voltage to said second circuit,    a buffer circuit, connected to said first power supply voltage and the ground, wherein input signal of said input terminal is supplied to said buffer circuit and output signal of said buffer circuit for driving said internal circuit is generated, and    a pull-up resistor and a pull up diode connected in series with said pull-up resistor, coupled between said input terminal and said first power supply voltage, wherein said pull-up diode is provided to a direction such that the anode of said pull-up diode is on the side of said first power supply voltage, and the cathode of said pull-up diode is on the side of said input terminal.    
   
   
       22 . The interface system according to  claim 21 , wherein said second circuit has a voltage surge protection diode connected between said input terminal and the ground, wherein said voltage surge protection diode is provided to a direction such that the anode of said voltage surge protection diode is on the side of the ground, and the cathode of said voltage surge protection diode is on the side of said input terminal.  
   
   
       23 . An interface system for interfacing two circuits, comprising: 
 a first circuit having    a push-pull type output circuit coupled between a first power supply voltage and the ground said push-pull type output circuit controlled to be ON or OFF by a control signal, and    an output terminal for outputting an output signal of said first circuit;    and a second circuit having    an input terminal connected to said output terminal of said first circuit for receiving the output signal of said first circuit as the input signal to said second circuit,    an internal circuit having a second power supply voltage higher than said first power supply voltage as an operating voltage,    a voltage regulation circuit obtaining said first supply power voltage from said second supply voltage,    a buffer circuit, connected to said first power supply voltage and the ground, wherein input signal of said input terminal is supplied to said buffer circuit and output signal of said buffer circuit for driving said internal circuit is generated, and    a pull-up resistor and a pull-up diode connected in series with said pull-up resistor, coupled between said input terminal and said first supply voltage, wherein said pull-up diode is provided to a direction such that the anode of said pull-up diode is on the side of said first power supply voltage, and the cathode of said pull-up diode is on the side of said input terminal.    
   
   
       24 . The interface system according to  claim 23 , wherein said second circuit has a voltage surge protection diode connected between said input terminal and the ground, wherein said voltage surge protection diode is provided to a direction such that the anode of said voltage surge protection diode is on the side of the ground, and the cathode of said voltage surge protection diode is on the side of said input terminal.  
   
   
       25 . An circuit, comprising: 
 an input terminal for inputting an input signal;    a pull-up resistor and a pull-up diode connected in series with said pull-up resistor, coupled between said input terminal and a first power supply voltage, wherein said pull-up diode is provided to a direction such that the anode of said pull-up diode is on the side of said first power supply voltage, and the cathode of said pull-up diode is on the side of said input terminal;    an internal circuit having a second power supply voltage higher than said first power supply voltage as an operating voltage,    a buffer circuit fed with said input signal and connected to said first power supply voltage and the ground, said buffer circuit generating output signal for driving said internal circuit, and    a voltage regulation circuit for forming said first power supply voltage from said second power supply voltage.    
   
   
       26 . An circuit, comprising: 
 an input terminal for inputting an input signal;    a pull-up resistor and a pull-up diode connected in series with said pull-up resistor, coupled between said input terminal and a first power supply voltage, wherein said pull-up diode is provided to a direction such that the anode of said pull-up diode is on the side of said first power supply voltage, and the cathode of said pull-up diode is on the side of said input terminal;    an internal circuit having a second power supply voltage higher than said first power supply voltage as an operating voltage,    a terminal for supplying said first power supply voltage to said second circuit,    a buffer circuit fed with said input signal and connected to said first power supply voltage and the ground, said buffer circuit generating output signal for driving said internal circuit.