Fujitsu Corporation

Fujitsu Semiconductor Limited

Fujitsu Microelectronics Limited

Katsuhiro Mori

Shinya Fujioka

Kota Hara

Toru Koga

Yoshiaki Okuyama

Masahiro Niimi

Waichiro Fujieda

Jun Ohno

Akihiro Funya

In a semiconductor memory device which uses a same pad for an address input and data input/output, and has an input circuit and data output circuit connected to the pad, an output of the data output circuit is turned to a high impedance state in accordance with a chip enable signal, output enable signal, and address capture signal, at a stand-by time, output disable time, and address capture period, and thereby, it becomes possible to start an internal read operation even before the address capture period is finished, and a high-speed operation becomes possible.

Semiconductor memory device

A semiconductor memory device which has a normal memory cell array and a redundant memory cell array for replacing a failure bit in the normal memory cell array, having: a memory cell array having a plurality of word lines, a plurality of bit line pairs crossing the word lines, and a plurality of memory cells placed at the crossing positions; and a plurality of sense amplifier circuits which are placed between adjacent memory cell arrays and are shared by bit line pairs of memory cell arrays on both sides. And a current interrupting circuit for disconnecting the sense amplifier and the bit line pairs in a column having a failure is formed respectively between the sense amplifier circuit and the bit line pairs on both sides. By this current interrupting circuit, short-circuit current from the sense amplifier circuit to the shorted area can be suppressed.

Dynamic random access memory (DRAM) for suppressing a short-circuit current

A memory circuit has: a real cell array; a parity generating circuit for generating a parity bit from data of the real cell array; a parity cell array; a refresh control circuit, which sequentially refreshes the real cell array, and when an internal refresh request and a read request coincide, prioritizes a refresh operation; a data recovery section, which, in accordance with the parity bit read out from the parity cell array, recovers data read out from the real cell array; and an output circuit for outputting data from the real cell array. Further, the memory circuit has a test control circuit, which, at a first test mode, prohibits a refresh operation for the real cell array to output data read out from the real cell array, and, at a second test mode, controls the output circuit so as to output data read out from the parity cell array.

Memory circuit having parity cell array

A mode set entry circuit outputs a latch timing signal at the timing at which the combination of a plurality of commands is detected. A first address latch circuit retains mode designation data for designating the operation mode in response to the latch timing signal and outputs the retained mode designation data. Next, a second address latch circuit retains the mode designation data outputted by the first address latch circuit in response to a latch timing signal indicating the end of the commands in the combination of the plural commands, and outputs the retained mode designation data.

A power supply circuit includes a first NMOS-type current mirror circuit which compares a first potential with a second potential, a second NMOS-type current mirror circuit which compares the first potential with a third potential, and a potential setting circuit which adjusts the first potential in response to outputs of the first and second NMOS-type current mirror circuits, such that the first potential falls between the second potential and the third potential.

Reduced potential generation circuit operable at low power-supply potential

Operating margins of a semiconductor integrated circuit are reliably tested at low power consumption by switching power supply circuits between normal operation mode wherein a first step-up power supply serves both memory core and a step-down power supply, and testing mode wherein the memory core is powered by an external testing power supply that provides a fluctuating voltage for testing, and the step-down power supply is served by a second step-up power supply.

Semiconductor integrated circuit and a testing method thereof

First and second voltage generators generate a first internal power supply voltage to be supplied to a first internal power supply line and a second internal power supply voltage to be supplied to a second internal power supply line, respectively. A short circuit shorts the first and second internal power supply lines when operations of both the first and second voltage generators are suspended. The first and second internal power supply lines become floating, and charges stored in the respective internal power supply lines drain out gradually. Here, since the charges are redistributed to both of the internal power supply lines, the first and second internal power supply voltages become equal in value as they drop off. Consequently, the first and second internal power supply voltages can be prevented from inversion, and internal circuits connected to both the first and second internal power supply lines can be precluded from malfunctioning.

Semiconductor integrated circuit

A redundancy memory circuit stores a defect address indicating a defective memory cell row. A redundancy control circuit disables the defective memory cell row corresponding to the defect address stored in the redundancy memory circuit and enables a redundancy memory cell row in the memory block containing the defective memory cell row. Moreover, in the other memory blocks, the redundancy control circuit disables memory cell rows corresponding to the defective memory cell row and enables redundancy memory cell rows instead of these memory cell rows. Consequently, not only the memory block having the defective memory cell row but one of the memory cell rows in the other memory blocks is always also relieved. Thus, the redundancy memory circuit can be shared among all the memory blocks with a reduction in the number of redundancy memory circuits. As a result, the semiconductor memory can be reduced in chip size.

Semiconductor memory

Upon receiving a level of a second node through a third switch in the first half of a first period, a holding circuit outputs it as a fuse signal indicating a blown-out state of a fuse. Since the third switch turns off in the second half of the first period, a change in level of the second node occurring thereafter will not affect data in the holding circuit, whereby prevents malfunction of a fuse circuit. With the fuse blown, a level of a first node gets fixed at that of a second power supply line after the first period. This eliminates a voltage difference between both ends of the fuse, thereby preventing a growback. No occurrence of growback makes just one fuse blowing sufficient for the fuse circuit even with the fuse not completely cut off. This consequently shortens a time for blowing the fuse in a test process.

Fuse circuit

A semiconductor device includes a plurality of word lines selectable in a predetermined mode, and a circuit that precharges the plurality of word lines selected in the predetermined mode in a time division manner.

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Kawasaki, Japan

Katsuhiro Mori