Trap and delay pulse generator for a high speed clock

• US 6,175,526 B1
• Filed: 01/31/2000
• Issued: 01/16/2001
• Est. Priority Date: 06/05/1998
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Morgan, Donald M.
• Primary Examiner(s): Nguyen, Viet Q.
• Application Number:
  US09/494,492
• Time in Patent Office: 351 Days
• Field of Search: 365/194, 365/233, 365/230.08, 365/189.05, 365/191, 327/149
• US Class Current: 365/194
• CPC Class Codes: G11C 7/1051 Data output circuits, e.g. read-out amplifiers, data output buffers, data output registers, data output level conversion circuits
• CPC Class Codes: G11C 7/106 Data output latches
• CPC Class Codes: G11C 7/22 Read-write [R-W] timing or clocking circuits; Read-write [R-W] control signal generators or management

Abstract

A trap and delay pulse generator for command signals triggered off of a high speed clock allows a device to develop signals before initiating a function and to complete the function after the clock pulse expires and allows overlap of sequential functions. When a device receives a sequence of clock pulses triggering command signals it is necessary that the device complete the functions after the clock pulse expires before receiving a new command signal triggered off of a subsequent clock pulse. The trap and delay pulse generator latches the command signal triggered off of the clock pulse and delays it to ensure an operation is ready to proceed even if the clock signal expires before the present command is completed.

Claims

1. A trap and delay pulse generator for a synchronous dynamic random access memory (SDRAM) comprising:

an input stage for receiving a externally generated signal triggered off of a high speed clock pulse;

a delay path coupled to the input stage for receiving and delaying the externally generated signal;

an enable circuit coupled to the delay path for receiving and passing through the externally generated signal when the SDRAM performs a READ function;

a latch circuit having a delay element coupled to the enable circuit for receiving, latching and delaying the externally generated signal provided by the enable circuit, wherein delay of the externally generated signal ensures the SDRAM has developed signal levels for a READ function before initiation of the READ function; and

a one-shot pulse generator coupled to the latch for receiving the latched externally generated signal and generating an output pulse for initiation of the READ function.

2. The trap and delay pulse generator of claim 1 wherein each succeeding READ function is able to overlap the last READ cycle by the delay time of the delay path.

3. The trap and delay pulse generator of claim 1 wherein the externally generated signal is triggered of a column address select signal.

4. The trap and delay pulse generator of claim 1 wherein the latch circuit can be automatically reset during operation.

5. The trap and delay pulse generator of claim 1 further comprising:

a pulse width circuit coupled to the one-shot pulse generator for adjusting a pulse width of the output pulse.

6. The trap and delay pulse generator of claim 1 further comprises:

a control input coupled to the one-shot pulse generator for inhibiting generation of the output pulse if the enable circuit becomes disabled after passing the externally generated signal to the latch circuit.

7. The trap and delay pulse generator of claim 1 wherein the delay path is adjustable.

8. A synchronous dynamic random access memory (SDRAM) comprising:

a plurality of memory cells, each memory cell electrically coupled to one of a plurality of true and complementary digit lines;

a plurality of sense amplifiers, each sense amplifier electrically coupled to one of the plurality of true and complimentary digit lines for sensing and amplifying a voltage differential to a corresponding input/output line pair;

a plurality of helper flip flops, each helper flip flop is electrically coupled to the input/output line pair for amplifying the voltage differential into a full data signal to be used at an output data buffer; and

a trap and delay pulse generator circuit coupled to the plurality of helper flip flops for delaying activation of a helper flip flop during a READ function if the SDRAM input/output lines have not developed sufficient signal levels for a READ function, the trap and delay pulse generator circuit comprising;

an input stage for receiving an externally generated signal triggered off of a high speed clock pulse;

an enable circuit coupled to the input stage for receiving and passing through the externally generated signal when the synchronous dynamic random access memory performs a READ function;

a latch circuit having a delay element coupled to the enable circuit for receiving and delaying the externally generated signal provided by the enable circuit, wherein delay of the externally generated signal ensures the SDRAM input/output lines have developed adequate signal levels for a READ function before initiation of the READ function; and

a one-shot pulse generator coupled to the latch for receiving the latched externally generated signal and generating an output pulse for activating the helper flip flop in performance of the READ function.

9. The synchronous dynamic random access memory of claim 8 wherein the helper flip flop consist of a bi-stable latch.

10. A computer system, the computer system comprising a synchronous dynamic random access memory (SDRAM), the memory device including:

a plurality of storage cells coupled to a row line and a digit line;

a plurality of column lines coupled to a digit line pair and an input/output line pair;

row addressing circuitry coupled to the row lines for selecting a row for a storage cell;

a sense amplifier coupled to the digit line that detects the voltage stored in the selected storage cell and amplifies a differential voltage on a digit line and a digit line complement;

column addressing circuitry coupled to the column lines for selecting a column for the selected digit line and digit line complement to be coupled to an input/output line pair;

a helper flip flop coupled to the input/output line pair for amplifying the voltage differential into a full data signal to be used at an output data buffer; and

a trap and delay pulse generator circuit coupled to the helper flip flop for delaying activation of a helper flip flop during a new READ function if the SDRAM has not developed sufficient signal levels for a READ function, the trap and delay pulse generator circuit comprising;

an input stage for receiving a column address latch signal triggered off of a high speed clock pulse;

a delay path coupled to the input stage for receiving and delaying the column address latch signal;

an enable circuit coupled to the delay path for receiving and passing through the column address latch signal when the SDRAM performs a READ function;

a latch circuit having a delay element coupled to the enable circuit for receiving, latching and delaying the column address latch signal provided by the enable circuit, wherein delay of the column address latch signal ensures the SDRAM has developed adequate signal levels for a READ function before initiation of the READ function; and

a one-shot pulse generator coupled to the latch for receiving the latched column address latch signal and generating an output pulse for activating the helper flip flop in performance of the READ function.

11. The computer system of claim 10 further comprising a pulse width circuit coupled to the one-shot pulse generator for adjusting a pulse width of the output pulse.

12. The computer system of claim 10 further comprising a control input coupled to the one-shot pulse generator for inhibiting generation of the output pulse after the clock pulse has been latched if the new READ command is not to be performed.

13. The computer system of claim 10 wherein the delay path is adjustable.

14. The computer system of claim 10 wherein the helper flip flop consists of a bi-stable latching circuit.

15. A method of delaying application of a command signal within a device if the device is not ready to execute the command signal, the method comprising:

receiving the command signal triggered off of a clock pulse;

enabling the command signal if the device is to perform a particular function corresponding to the received command signal;

latching the command signal;

delaying the latched command signal to allow time for completion of preparations corresponding to the received command signal; and

generating an output pulse for initiation of the function corresponding to the received command signal.

16. The method of claim 15 further comprising adjusting a pulse width of the output pulse.

17. The method of claim 15 further comprising inhibiting generation of the output pulse after the command signal has been latched if the command signal becomes disabled.

18. The method of claim 15 further comprising unlatching the command signal.

19. A method of allowing a synchronous dynamic random access memory (SDRAM) to complete a first READ function before performing a second READ function if the SDRAM is still performing the first READ function, the method comprising:

receiving an externally generated signal triggered off of a high speed clock pulse;

enabling the externally generated signal if the SDRAM is to perform the second READ function;

latching the externally generated signal;

delaying the latched externally generated signal to ensure proper timing for completion of the first READ function; and

generating an output pulse for initiation of the second READ function.

20. The method of claim 19 further comprises adjusting a pulse width of the output pulse.

21. The method of claim 19 further comprising inhibiting generation of the output pulse after the column address latch signal has been latched if the column address latch signal becomes disabled.