Semiconductor storage device
A semiconductor storage device includes an SRAM memory cell composed of a drive transistor, a transfer transistor and a load transistor, an I/O circuit that is connected to bit lines connected to the memory cell, and an operating mode control circuit that switches an operating mode of the I/O circuit between a resume standby mode and a normal operation mode, wherein the I/O circuit includes a write driver that writes data to bit lines, a sense amplifier that reads data from the bit lines, a first switch inserted between the bit lines and the write driver, a second switch inserted between the bit lines and the sense amplifier, a precharge circuit that precharges the bit lines, and a control circuit that controls the first and second switches and the precharge circuit according to a signal from the operating mode control circuit.
1. A semiconductor device comprising:
a memory cell;
a pair of bit lines electrically coupled with the memory cell;
a word line extending in a direction crossing the pair of bit lines, and electrically coupled with the memory cell;
a precharge circuit electrically coupled with the memory cell via the pair of bit lines;
and
an operating mode control circuit electrically coupled with the precharge circuit via a precharge power supply line,
wherein the operating mode control circuit receives a first control signal and outputs a second control signal to the precharge circuit,
wherein the operating mode control circuit outputs a first potential to the precharge power supply line in a first mode that is set by the first control signal, and outputs a second potential lower than the first potential in a second mode that is set by the first control signal, and
wherein the precharge circuit comprises:
a first MOS transistor having a first source coupled with the precharge power supply line, a first drain coupled with one bit line of the pair of bit lines, and a first gate controlled by the second control signal, and
a second MOS transistor having a second source coupled with the precharge power supply line, a second drain coupled with the other bit line of the pair of bit lines, and a second gate controlled by the second control signal.
2. The semiconductor device of claim 1 , wherein the operating mode control circuit comprises:
a delay circuit which receives the first control signal and outputs a third control signal;
a third MOS transistor having a third gate and a third source both supplied with the first potential, and a third drain coupled with the precharge power supply line; and
a fourth MOS transistor having a fourth gate to receive the third control signal, a fourth source supplied with the first potential, and a fourth drain coupled with the precharge power supply line.
3. The semiconductor device of claim 2 , wherein the delay circuit comprises a plurality of buffers.
4. The semiconductor device of claim 1 , wherein the memory cells comprises:
a flip-flop having a first storage node, a second storage node, a first CMOS inverter having an output coupled to the first storage node and an input coupled to the second storage node, and a second CMOS inverter having an output coupled to the second storage node and an input coupled to the first storage node, the first CMOS inverter including a first load PMOS transistor and a first drive NMOS transistor, the second CMOS inverter including a second load PMOS transistor and a second drive NMOS transistor;
a first transfer NMOS transistor having a source-drain path coupled between the first storage node and the one bit line of the pair of bit lines and having a gate coupled to the word line, and
a second transfer NMOS transistor having a source-drain path coupled between the second storage node and the other bit line of the pair of bit lines and having a gate coupled to the word line,
wherein the first and second load PMOS transistors are supplied with the first potential.
5. The semiconductor device of claim 1 , comprising an I/O circuit connected to the pair of bit lines, wherein the I/O circuit comprises:
the precharge circuit;
a write driver coupled with the pair of bit lines via a first switch; and
a sense amplifier coupled with the pair of bit lines via a second switch.
6. The semiconductor device of claim 5 , wherein the I/O circuit comprises an I/O control circuit that outputs a third control signal.
7. The semiconductor device of claim 6 , wherein the I/O control circuit comprises a first inverter that outputs the third control signal.
8. The semiconductor device of claim 2 ,
wherein the third control signal is a high level in the second mode, and
wherein the third control signal is a low level in the first mode.
9. The semiconductor device of claim 1 , wherein the first mode is a normal operation mode, and the second mode is a resume standby mode.