Pre-charge tracking of global read lines in high speed SRAM
In embodiments of the invention, a memory circuit includes a static random access memory (SRAM), rows of M sense amplifiers, a global read precharge tracking control circuit controlling a precharge of global read lines, a sense amplifier output tracking circuit generating a reset sense amplifier signal for the sense amplifier control circuits, and a read delay circuit generating a trigger signal for the global read precharge tracking control circuit and the sense amplifier output tracking circuit and performing a fixed delay tracking of a read operation in a read cycle. A dummy global read line is coupled to the global read precharge tracking control circuit and returns from a half way to the top of the SRAM forming a tracking dummy global read line that determines a completion of the precharge of the global read lines before the sense amplifiers start discharging the global read lines in the read cycle.
1. A memory circuit, comprising:
a static random access memory including N banks of memory cells, each bank having M columns, where M and N are positive integers;
rows of M sense amplifiers, each row of the M sense amplifiers placed between two banks of the memory cells, each row of the M sense amplifiers coupled to a sense amplifier control circuit and a local input/output circuit, each column of the M sense amplifiers corresponding to a bit of the memory cell, the bit having corresponding global read lines;
a global read precharge tracking control circuit controlling a precharge of the global read lines using a track dummy global read line signal;
a sense amplifier output tracking circuit generating a reset sense amplifier signal for the sense amplifier control circuits; and
a read delay circuit generating a trigger signal for the global read precharge tracking control circuit and the sense amplifier output tracking circuit and performing a fixed delay tracking of a read operation in a read cycle;
wherein a dummy global read line is coupled to the global read precharge tracking control circuit and returns from a half way to the top of the static random access memory forming a tracking dummy global read line that determines a completion of the precharge of the global read lines before the sense amplifiers start discharging the global read lines in the read cycle.
2. The memory circuit of claim 1 , wherein an internal clock signal is provided to the read delay circuit and the sense amplifier output tracking circuit, respectively.
3. The memory circuit of claim 1 , wherein the trigger signal generated from the read delay circuit transitions to a LOW state after a fixed delay set in the read delay circuit, which triggers a sense amplifier to output latch tracking through the sense amplifier output tracking circuit, and also triggers switching OFF the precharge of the global read lines and the dummy global read line through the global read precharge tracking control circuit, and subsequently, the sense amplifiers in the local input/output circuit start discharging the global read lines depending on data stored in corresponding address locations in a bank in the read cycle, and a track global read line precharge signal starts discharging the track dummy global read line.
4. The memory circuit of claim 1 , where the track global read line precharge signal is a return signal of the global read line precharge signal from a half way to the right of the static random access memory.
5. The memory circuit of claim 1 , wherein the static random access memory includes a global input and output circuit that has M global input and output circuit elements and a dummy global input and output circuit that has a half number of dummy global input and output circuit elements less than the global input and output circuit, each global input and output circuit element is coupled to a corresponding column of the static random access memory, and the M sense amplifiers in the each column are connected together and coupled to the corresponding global input and output circuit element of the corresponding column.
6. The memory circuit of claim 5 , wherein an inverter is coupled to the global input and output circuit and the dummy global input and output circuit at the half way of the global input and output circuit and the end of the dummy global input and output circuit, coverts the global read line precharge signal from the global input and output circuit, and sends the converted global read line precharge signal to the dummy global input and output circuit.
7. The memory circuit of claim 6 , wherein the global read line precharge signal travels along the global input and output circuit and returns to the global read precharge tracking control circuit from a half way to the right of the static random access memory through the inverter and the dummy global input and output circuit, forming a track global read line precharge signal that discharges the tracking dummy global read line signal in the read cycle.
8. The memory circuit of claim 1 , wherein each sense amplifier control circuit includes a sense amplifier precharge circuit for precharging the sense amplifier by generating a sense amplifier reset signal and a sense amplifier to output generator that generates a sense amplifier enable signal for the each row of the M sense amplifiers, both are triggered by the reset sense amplifier signal generated from the sense amplifier output tracking circuit, and the sense amplifier to output generator also receives the global read line precharge signal from the global read precharge tracking control circuit.
9. The memory circuit of claim 1 , wherein the sense amplifier output tracking circuit is a sense-amplifier to output latch.
10. The memory circuit of claim 1 , wherein the read delay circuit includes two individual inverters coupled to NOR gate inputs of a NOR gate, respectively, and an inverter block having an even number of inverters connected in series and coupled to one of the two individual inverters.
11. The memory circuit of claim 1 , wherein global read precharge tracking control circuit includes a first circuit having a single inverter and a second circuit having two NAND gates, each NAND gates has an inverter coupled to a NAND gate input, and a NAND gate output of a first NAND gate is couple to another NAND gate input of a second NAND gate.
12. The memory circuit of claim 11 , wherein the track global read line precharge signal is input to the first circuit and the dummy global read line is output from the first circuit.
13. The memory circuit of claim 11 , wherein the trigger signal, the track dummy global read line signal and the track reset sense amplifier signal are input to the second circuit and the global read line precharge signal is output from the second circuit.
14. The memory circuit of claim 1 , wherein the reset sense amplifier signal returns from a half way to the top of the static random access memory forming a track reset sense amplifier signal that is sent into the read delay circuit and the global read precharge tracking control circuit, respectively, in the read cycle.
15. The memory circuit of claim 1 , wherein a default state of the track reset sense amplifier signal is HIGH, when a rising edge of the internal clock arrives in the read cycle, the track reset sense amplifier signal switches to LOW, when the internal clock is reset by the sense amplifier to output tracking circuit to LOW, the track reset sense amplifier signal transitions to HIGH.
16. A method for a precharge tracking of global read lines in a high speed static random access memory system, the method comprising the steps of:
generating a trigger signal from a read delay circuit by receiving an internal clock and a track sense amplifier rest signal in a read cycle, wherein when a rising edge of the internal clock arrives, the track reset sense amplifier signal goes to LOW from a default state of HIGH;
forwarding the trigger signal into a sense amplifier to output tracking circuit for generating a reset sense amplifier signal for sense amplifier control circuits to reset sense amplifiers and a global read line precharge control circuit for generating a global read line precharge signal for precharge of global read lines and dummy global read lines, respectively;
switching OFF the trigger signal after a fixed delay set in the read delay circuit in the read cycle;
triggering a sense amplifier to output latch tracking through the sense amplifier to output tracking circuit, and simultaneously triggering switching OFF the precharge of global read lines and dummy global read lines;
discharging one of the global read lines in a bit depending on data stored in corresponding address locations in a bank of the static random access memory by sense amplifiers, and simultaneously discharging a track dummy global read lines signal coupled to the global read line precharge control circuit by a track global read line precharge signal; and
resetting the internal clock to LOW, resetting the track reset sense amplifier signal to HIGH, then triggering switching ON of the precharge of the global read lines and the dummy global read lines by generating a rising edge of the global read line precharge signal, which precharges the track dummy global read lines and makes the static random access memory ready for the next read cycle.
17. The method of claim 16 , wherein the read delay circuit sets the trigger signal HIGH along with the resetting the internal clock and a HIGH state of the track reset sense amplifier signal.
18. The method of claim 16 , wherein in the step of the triggering switching OFF the precharge of the global read lines and the dummy global read lines includes the track dummy global read line signal is HIGH through a falling edge of the global read line precharge signal.
19. The method of claim 16 , wherein if the track dummy global read line signal is not HIGH, the trigger signal wait for an arrival of a rising edge of the track dummy global read line signal.
20. The method of claim 19 , wherein the track dummy global read line signal is a return signal of the dummy global read lines coupled to the global read line precharge control circuit from a half way to the top of the static random access memory.
21. The method of claim 16 , wherein the track global read line precharge signal is a return signal of the global read line precharge signal from a half way to the right of the static random access memory.
22. The method of claim 16 , wherein the track reset sense amplifier signal is a return signal of the reset sense amplifier signal from a half way to the top of the static random access memory.