Semiconductor memory device capable of testing data line redundancy replacement circuit
View Patent ↗In a shift switch circuit for replacing a data line, a transmission gate circuit connecting node N2 corresponding to ith write data line to node N4 corresponding to ith read data line is provided. An operation of the shift switch circuit can be confirmed according to whether or not an output corresponding to provided data input signal D<i> is observed as data output signal Q<i>. Preferably, a transmission gate connecting i+1th write data line to an output data line is further provided, in order to further ensure operation confirmation. When a fuse circuit is set to replace a data line, ratio of successful chip repairing will be higher.
1. A semiconductor memory device having a test mode and a normal mode as operation modes, comprising:
a memory cell array divided into a plurality of areas;
a plurality of read data lines provided corresponding to said plurality of areas, respectively, to communicate data;
a plurality of write data lines provided corresponding to said plurality of areas, respectively, to communicate data;
a replacement control circuit holding replacement information in a non-volatile manner and outputting a shift control signal in accordance with said replacement information; and
a data line shift circuit selecting a prescribed number of read data lines to be used from said plurality of read data lines and selecting a prescribed number of write data lines to be used from said plurality of write data lines, said data line shift circuit including
a first switch circuit connecting, in said normal mode, either one of first and second write data lines of said plurality of write data lines to a first input node in accordance with said shift control signal and connecting, in said test mode, said first write data line to said first input node,
a second switch circuit connecting, in said normal mode, either one of first and second read data lines of said plurality of read data lines to a first output node in accordance with said shift control signal and connecting, in said test mode, said first read data line to said first output node, and
a first data transmission circuit activated in said test mode and transmitting data of said first write data line to said first read data line, wherein
said data line shift circuit further includes a second data transmission circuit activated in said test mode to transmit data of said second write data line to said second read data line.
2. The semiconductor memory device according to claim 1 , wherein
said first and second data transmission circuits transmit data in accordance with activation of first and second test signals respectively;
said data line shift circuit further includes a signal output portion, in said test mode, inactivating a shift enable signal in accordance with activation of said first test signal and activating said shift enable signal in accordance with activation of said second test signal, and in said normal mode, activating said shift enable signal in accordance with said shift control signal;
said first switch circuit includes
a first transmission gate circuit connected between said first write data line and said first input node and being in a non-conducting state and in a conducting state respectively in accordance with activation and inactivation of said shift enable signal, and
a second transmission ate circuit connected between said second write data line and said first input node and being in a conducting state and in a non-conducting state respectively in accordance with activation and inactivation of said shift enable signal; and
said second switch circuit includes
a third transmission gate circuit connected between said first read data line and said first output node and being in a non-conducting state and in a conducting state respectively in accordance with activation and inactivation of said shift enable signal, and
a fourth transmission gate circuit connected between said second read data line and said first output node and being in a conducting state and in a non-conducting state respectively in accordance with activation and inactivation of said shift enable signal.