Semiconductor device, electronic device, and method of testing the semiconductor device

Abstract

A semiconductor device includes a supply terminal that receives a supply voltage from an outside and supplies the supply voltage to a power supply line, a ground terminal that receives a ground voltage from the outside, a first I/O terminal that conducts a logical input signal from the outside, a first diode that is disposed between the supply terminal and the first I/O terminal so that the supply terminal is located on a cathode side and the first I/O terminal is located on an anode side, and a determination unit that compares voltages of the power supply line and the first I/O terminal, and outputs an abnormal signal when the voltage of the supply terminal is less than the voltage of the first I/O terminal.

What is claimed is: 
     
         1 . A semiconductor device, comprising:
 a supply terminal that receives a supply voltage from an outside;   a ground terminal that receives a ground voltage from the outside;   a first I/O terminal that conducts at least one of input and output of a signal with respect to the outside;   a first diode that is disposed between the supply terminal and the first I/O terminal so that the supply terminal is located on a cathode side and the first I/O terminal is located on an anode side;   a determination unit that determines whether a voltage of the supply terminal is less than a voltage of the first I/O terminal when a signal of high level equal to the supply voltage is input to the first I/O terminal, and   wherein the determination unit outputs an abnormal signal when the voltage of the supply terminal is less than the voltage of the first I/O terminal, and   wherein the semiconductor device further comprises:   a central processing unit; and   a control circuit that issues an interrupt notice to the central processing unit upon receiving the abnormal signal.   
     
     
         2 . The semiconductor device according to  claim 1 ,
 wherein the determination unit outputs a reset signal when the voltage of the supply terminal is less than the voltage of the first I/O terminal, and   wherein the semiconductor device further comprises an internal circuit that conducts initialization upon receiving the reset signal.   
     
     
         3 . The semiconductor device according to  claim 1 ,
 wherein the semiconductor device has, as operation modes, a normal mode and a power saving mode that is smaller in power consumption than the normal mode,   wherein the semiconductor device further comprises a mode control circuit that switches the operation mode, and   wherein the mode control circuit switches the operation mode from the normal mode to the power saving mode when receiving a determination result from the determination unit that the voltage of the supply terminal is less than the voltage of the first I/O terminal.   
     
     
         4 . The semiconductor device according to  claim 1 , further comprising an output terminal that outputs a determination result of the determination unit to the outside. 
     
     
         5 . The semiconductor device according to  claim 1 , further comprising:
 a second I/O terminal that conducts at least one of input and output of the signal with respect to the outside;   a second diode that is disposed between the supply terminal and the second I/O terminal so that the supply terminal is located on the cathode side and the second I/O terminal is located on the anode side; and   a selector circuit that is coupled to the first and second I/O terminals, selects one of the first and second I/O terminals, and outputs the voltage of the selected I/O terminal to the determination unit,   wherein when the signal of the high level equal to the supply voltage is input to both of the first and second I/O terminals, the determination unit determines whether the voltage of the supply terminal is less than the voltage of the first I/O terminal if the determination unit receives the voltage of the first I/O terminal from the selector circuit, and determines whether the voltage of the supply terminal is less than the voltage of the second I/O terminal if the determination unit receives the voltage of the second I/O terminal from the selector circuit.   
     
     
         6 . The semiconductor device according to  claim 1 , further comprising:
 a second I/O terminal that conducts at least one of input and output of the signal with respect to the outside;   a second diode that is disposed between the supply terminal and the second I/O terminal so that the supply terminal is located on the cathode side and the second I/O terminal is located on the anode side;   a first sample-hold circuit that is coupled to the first I/O terminal, and captures and holds the voltage of the first I/O terminal;   a second sample-hold circuit that is coupled to the second I/O terminal, and captures and holds the voltage of the second I/O terminal; and   a selector circuit that is coupled to the first and second sample-hold circuits, selects one of the first and second sample-hold circuits, and outputs the voltage held in the selected sample-hold circuit to the determination unit, and   wherein when the supply voltage or the signal of the high level equal to the supply voltage is input to both of the first and second I/O terminals, the determination unit determines whether the voltage of the supply terminal is less than the voltage of the first I/O terminal if the determination unit receives the voltage of the first I/O terminal held by the first sample-hold circuit from the selector circuit, and determines whether the voltage of the supply terminal is less than the voltage of the second I/O terminal held by the second sample-hold circuit if the determination unit receives the voltage of the second I/O terminal held by the second sample-hold circuit from the selector circuit.   
     
     
         7 . The semiconductor device according to  claim 1 , further comprising:
 one or a plurality of second I/O terminals that conduct at least one of input and output of the signal with respect to the outside; and   one or a plurality of second diodes that are disposed in correspondence with the respective second I/O terminals, and each disposed between the supply terminal and the corresponding second I/O terminal so that the supply terminal is located on the cathode side and the corresponding second I/O terminal is located on the anode side,   wherein when the signal of the high level equal to the supply voltage is input to the first I/O terminal or the second I/O terminals, the determination unit determines whether the voltage of the supply terminal is less than the respective voltages of the first I/O terminal and the second I/O terminals, and   wherein when the voltage of the supply terminal is less than all the voltages of the first I/O terminal and the second I/O terminals, the determination unit outputs a signal indicative of a coupling failure of the supply terminal and the outside.   
     
     
         8 . The semiconductor device according to  claim 1 , further comprising a second diode and a first switch element which are coupled in series with each other between the supply terminal and the first I/O terminal,
 wherein the second diode is coupled so that the supply terminal is located on the cathode side, and the first I/O terminal is located on the anode side, and   wherein the determination unit turns on the first switch element when the voltage of the supply terminal is less than the voltage of the first I/O terminal.   
     
     
         9 . The semiconductor device according to  claim 1 , further comprising:
 a second I/O terminal that conducts at least one of input and output of the signal with respect to the external; and   a second diode that is disposed between the ground terminal and the second I/O terminal so that the ground terminal is located on the anode side and the second I/O terminal is located on the cathode side, the determination unit further determining whether the voltage of the ground terminal is greater than the voltage of the second I/O terminal when a signal of low level equal to the ground voltage is input to the second I/O terminal;   a third diode and a first switch element which are coupled in series with each other between the supply terminal and the first I/O terminal; and   a fourth diode and a second switch element which are connected in series with each other between the ground terminal and the second I/O terminal,   wherein the third diode is coupled so that the supply terminal is located on the cathode side, and the first I/O terminal is located on the anode side,   wherein the fourth diode is coupled so that the ground terminal is located on the anode side, and the second I/O terminal is located on the cathode side,   wherein the determination unit turns on the first switch element when the voltage of the supply terminal is less than the voltage of the first I/O terminal, and   wherein the determination unit turns on the second switch element when the voltage of the ground terminal is greater than the voltage of the second I/O terminal.   
     
     
         10 . A semiconductor device, comprising:
 a supply terminal that receives a supply voltage from an outside and supplies the supply voltage to a power supply line;   a ground terminal that receives a ground voltage from the outside;   a first I/O terminal that conducts a logical input signal from the outside;   a first diode that is disposed between the supply terminal and the first I/O terminal so that the supply terminal is located on a cathode side and the first I/O terminal is located on an anode side;   a determination unit that compares voltages of the power supply line and the first I/O terminal, and outputs an abnormal signal when the voltage of the supply terminal is less than the voltage of the first I/O terminal;   a central processing unit; and   a control circuit that issues an interrupt notice to the central processing unit upon receiving the abnormal signal.