Refresh signal generating circuit
A refresh signal generating circuit of a semiconductor memory device includes a flag signal generator which generates a flag signal in response to a refresh signal and a precharge signal, a clock enable signal buffer which generates first and second buffer enable signals based on an external clock enable signal in response to the flag signal, and a chip select signal buffer which generates an internal chip select signal based on an external chip select signal in response to the flag signal.
1. A refresh signal generating circuit comprising:
a flag signal generator for generating a flag signal in response to a refresh signal and a precharge signal;
a clock enable signal buffer for generating first and second buffer enable signals based on an external clock enable signal in response to the flag signal; and
a chip select signal buffer for generating an internal chip select signal based on an external chip select signal in response to the flag signal.
2. The refresh signal generating circuit of claim 1 , wherein the flag signal generated by the flag signal generator is enabled in an all bank refresh operation.
3. The refresh signal generating circuit of claim 2 , wherein the flag signal generated by the flag signal generator is disabled at the completion of the all bank refresh operation.
4. The refresh signal generating circuit of claim 1 , wherein the flag signal generator includes:
a driving unit for selectively generating the flag signal in response to the refresh signal and the precharge signal; and
a latch for latching the flag signal.
5. The refresh signal generating circuit of claim 1 , wherein the first and second buffer enable signals generated by the clock enable signal buffer are disabled in an all bank refresh operation.
6. The refresh signal generating circuit of claim 1 , further comprising a clock buffer which generates first and second internal clocks based on an external clock in response to the first buffer enable signal.
7. The refresh signal generating circuit of claim 6 , wherein the clock buffer stops generation of the first and second internal clocks in an all bank refresh operation.
8. The refresh signal generating circuit of claim 1 , further comprising a command address buffer which generates an internal command address signal based on an external command address signal in response to the second buffer enable signal.
9. The refresh signal generating circuit of claim 8 , wherein the internal command address signal generated by the command address buffer is disabled to a first voltage level regardless of the external command address signal in an all bank refresh operation.
10. The refresh signal generating circuit of claim 1 , wherein the internal chip select signal generated by the chip select signal buffer is set to a second voltage level regardless of the external chip select signal in an all bank refresh operation.