U.S. patent application number 10/730356 was filed with the patent office on 2005-05-26 for high speed single ended sense amplifier with built-in multiplexer.
This patent application is currently assigned to Sun Microsystems, Inc. Invention is credited to Kant, Shree, Tam, Kenway W..
Application Number | 20050110527 10/730356 |
Document ID | / |
Family ID | 34592504 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050110527 |
Kind Code |
A1 |
Tam, Kenway W. ; et
al. |
May 26, 2005 |
HIGH SPEED SINGLE ENDED SENSE AMPLIFIER WITH BUILT-IN
MULTIPLEXER
Abstract
A first sense amp circuit includes a pre-charge circuit, a
keeper circuit, a select device and a driver device. The pre-charge
circuit coupled to an input data line, the input data line being
coupled to an input of a first inverter. The keeper circuit coupled
in parallel with the first inverter. The select device coupled to a
discharge path of the first inverter. The driver device coupled in
parallel to an output data line of the first inverter.
Inventors: |
Tam, Kenway W.; (Cupertino,
CA) ; Kant, Shree; (Union City, CA) |
Correspondence
Address: |
MARTINE PENILLA & GENCARELLA, LLP
710 LAKEWAY DRIVE
SUITE 200
SUNNYVALE
CA
94085
US
|
Assignee: |
Sun Microsystems, Inc
Santa Clara
CA
|
Family ID: |
34592504 |
Appl. No.: |
10/730356 |
Filed: |
November 24, 2003 |
Current U.S.
Class: |
327/51 |
Current CPC
Class: |
G11C 7/067 20130101;
H03K 3/356104 20130101 |
Class at
Publication: |
327/051 |
International
Class: |
H03F 003/45 |
Claims
What is claimed is:
1. A first sense amp circuit comprising: a pre-charge circuit
coupled to an input data line, the input data line being coupled to
an input of a first inverter; a keeper circuit coupled in parallel
with the first inverter; a select device coupled to a discharge
path of the first inverter; and a driver device coupled in parallel
to an output data line of the first inverter.
2. The circuit of claim 1, further comprising a half latch circuit
coupled to the input data line.
3. The circuit of claim 2, wherein the half latch circuit includes
a first input and a second input, the first input coupled to an
inverse of a pre-charge control signal, the second input coupled to
the output of the first inverter.
4. The circuit of claim 1, wherein the select device includes a
select control signal coupled to a control input of the select
device.
5. The circuit of claim 1, wherein the select device controls the
discharging of the first inverter.
6. The circuit of claim 1, wherein the driver device includes a
NAND gate and a second inverter, the NAND gate having a first input
coupled to a select control signal and a second input coupled to an
output of the second inverter, the second inverter having an input
coupled to the output of the first inverter, the output of the NAND
gate being coupled to the output of the first inverter.
7. The circuit of claim 1, wherein the driver device is not in
series with a data signal path through the first inverter.
8. The circuit of claim 1, further comprising: a second NAND gate
having a first input coupled to an output of the first inverter; a
second sense amp circuit having an output coupled to a first input
of the second NAND gate;
9. The circuit of claim 8, wherein a total delay through each of
the first sense amp circuit and the second sense amp circuit and
the second NAND is substantially equal to a two-gate delay.
10. The sense amp circuit of claim 1, wherein the first inverter
includes a skewed inverter.
11. A method of detecting a data signal level comprising:
pre-charging an input data line of a first inverter; receiving a
data signal on the input data line sufficient to cause the first
inverter to switch; outputting an output data signal level in less
than a two-gate delay; disabling the pre-charging the input data
line of the first inverter; and resetting the output data signal
level when a control signal is received.
12. The method of claim 11, wherein resetting the output data
signal level includes applying a predetermined voltage level to the
input data line of the first inverter.
13. The method of claim 11, wherein resetting the output data
signal level includes applying a predetermined voltage level to an
output of the first inverter when the select signal is
received.
14. The method of claim 11, wherein resetting the output data
signal level includes discharging the first inverter when the
select signal is received.
15. The method of claim 11, further comprising driving the output
data signal.
16. The method of claim 15, wherein driving the output data signal
includes applying a predetermined voltage level to an output of the
first inverter.
17. The method of claim 11, further comprising: coupling an output
of the first inverter to a first input of a second NAND gate; and
coupling an output of the second inverter to a second input of the
second NAND gate;
18. The method of claim 17, wherein a total delay through each of
the first sense amp circuit and the second sense amp circuit and
the second NAND is substantially equal to a two-gate delay.
19. The method of claim 11, wherein the first inverter includes a
skewed inverter.
20. A circuit comprising: a first sense amp circuit having a delay
substantially equal to a one-gate delay; a second sense amp circuit
having a delay substantially equal to a one-gate delay; a
multiplexer device having a first input coupled to an output of the
first sense amp circuit and a second input coupled to an output of
the second sense amp circuit; and a selection device coupled to a
selection control of each of the first sense amp circuit and the
second sense amp circuit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to sense amplifiers,
and more particularly, to methods and systems for a high-speed
sense amplifier.
[0003] 2. Description of the Related Art
[0004] A sense amplifier is often used to detect and couple (and
even amplify) a data signal level on a data line. Sense amplifiers
are typically used between a data output and a data input. By way
of example, a sense amplifier can be used to detect a data signal
level on a data line or data bus and then output the detected data
level to an input of a processor.
[0005] FIG. 1 is a typical sense amplifier circuit 100. A data
signal input line 112 conducts a data signal, such as from a data
line or bus, to the input of a skewed inverter 106. The skewed
inverter 106 senses a data signal on the data signal input line
112. When the data signal level passes a threshold level, the
skewed inverter 106 switches state. A keeper circuit 108 latches
the skewed inverter 106 once the sense amplifier has switched. An
inverter 102 and NMOS 104 form a pre-charge circuit to pull up the
data signal line 112 to reduce the time required for the data
signal to raise to the. As a result, the switching time for the
skewed inverter 106 is substantially reduced. An inverter 110 forms
an output buffer for the skewed inverter 106. The inverter 110 can
also amplify the output signal.
[0006] Output of the inverter 110 switches state approximately two
"gate delays" after the data signal on the data signal line 112
raises to the threshold level required to cause the skewed inverter
106 to switch. The two gate delays are the cumulative time required
for the skewed inverter 106 and the inverter 110 to switch.
[0007] In many applications and uses a sense amp needs to have less
than the two-gate delay so as to not unduly delay the output data
signal. In view of the foregoing, there is a need for a sense amp
having a delay of less than a two-gate delay.
SUMMARY OF THE INVENTION
[0008] Broadly speaking, the present invention fills these needs by
providing a sense amp circuit having less than a two-gate delay. It
should be appreciated that the present invention can be implemented
in numerous ways, including as a process, an apparatus, a system,
computer readable media, or a device. Several inventive embodiments
of the present invention are described below.
[0009] One embodiment includes a first sense amp circuit that
includes a pre-charge circuit, a keeper circuit, a select device
and a driver device. The pre-charge circuit coupled to an input
data line, the input data line being coupled to an input of a first
inverter. The keeper circuit coupled in parallel with the first
inverter. The select device coupled to a discharge path of the
first inverter. The driver device coupled in parallel to an output
data line of the first inverter.
[0010] A half latch circuit can also be coupled to the input data
line. The half latch circuit can include a first input and a second
input, the first input coupled to an inverse of a pre-charge
control signal, the second input coupled to the output of the first
inverter.
[0011] The select device can include a select control signal
coupled to a control input of the select device. The select device
can control the discharging of the first inverter.
[0012] The driver device can include a NAND gate and a second
inverter. The NAND gate having a first input coupled to a select
control signal and a second input coupled to an output of the
second inverter. The second inverter having an input coupled to the
output of the first inverter. The output of the NAND gate being
coupled to the output of the first inverter.
[0013] The driver device is not in series with a data signal path
through the first inverter. The circuit can also include a second
NAND gate having a first input coupled to an output of the first
inverter, a second sense amp circuit having an output coupled to a
first input of the second NAND gate. A total delay through each of
the first sense amp circuit and the second sense amp circuit and
the second NAND is substantially equal to a two-gate delay. The
first inverter can include a skewed inverter.
[0014] Another embodiment includes a method of detecting a data
signal level. The method includes pre-charging an input data line
of a first inverter, receiving a data signal on the input data line
sufficient to cause the first inverter to switch, outputting an
output data signal level in less than a two-gate delay, disabling
the pre-charging the input data line of the first inverter, and
resetting the output data signal level when a control signal is
received.
[0015] Resetting the output data signal level includes applying a
predetermined voltage level to the input data line of the first
inverter. Resetting the output data signal level can also include
applying a predetermined voltage level to an output of the first
inverter when the select signal is received. Resetting the output
data signal level can also include discharging the first inverter
when the select signal is received.
[0016] The output data signal can also be driven. Driving the
output data signal can include applying a predetermined voltage
level to an output of the first inverter.
[0017] The method can also include coupling an output of the first
inverter to a first input of a second NAND gate and coupling an
output of the second inverter to a second input of the second NAND
gate. A total delay through each of the first sense amp circuit and
the second sense amp circuit and the second NAND is substantially
equal to a two-gate delay. The first inverter can include a skewed
inverter.
[0018] Yet another embodiment provides a circuit that includes a
first sense amp circuit and a second sense amp circuit, each having
a delay substantially equal to a one-gate delay. The circuit also
includes a multiplexer device having a first input coupled to an
output of the first sense amp circuit and a second input coupled to
an output of the second sense amp circuit. A selection device
coupled to a selection control of each of the first sense amp
circuit and the second sense amp circuit can also be included.
[0019] The improved sense amplifier circuits described herein
provide an improved (faster) switching speed. The faster switching
speed allows the improved sense amplifier to be used in
applications requiring higher switching speeds.
[0020] The faster switching speed also allows the improved sense
amplifier to be used in combinations such as multiplexing two or
more sense amplifiers and still have substantially the same data
throughput delay as a single prior art sense amp circuit.
[0021] The improved sense amplifier circuits also substantially
reduce the conditional periods in the various data signals.
[0022] Other aspects and advantages of the invention will become
apparent from the following detailed description, taken in
conjunction with the accompanying drawings, illustrating by way of
example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The present invention will be readily understood by the
following detailed description in conjunction with the accompanying
drawings, and like reference numerals designate like structural
elements.
[0024] FIG. 1 is a typical sense amplifier circuit.
[0025] FIG. 2 is a sense amp circuit in accordance with one
embodiment of the present invention.
[0026] FIG. 3 is a block diagram of a pair of multiplexed sense amp
circuits, in accordance with one embodiment of the present
invention.
[0027] FIG. 4 is a sense amp circuit in accordance with one
embodiment of the resent invention.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0028] Several exemplary embodiments for a faster switching sense
amp circuit will now be described. It will be apparent to those
skilled in the art that the present invention may be practiced
without some or all of the specific details set forth herein.
[0029] A faster switching sense amp circuit allows the required
data signal to e more rapidly transmitted through the sense amp
circuit and therefore overall faster data transmission can be
accomplished. One embodiment includes a select device that allows
the sense amp circuit to be selected. The select device is not in
the data path through the sense amp circuit and therefore does not
add any gate delays to the to data path and therefore does not
affect the timing. An output driver in series with the output of
the sense amp circuit is no longer used. A NAND gate is used to
pull down the output of the sense amp circuit and effectively drive
the output of the sense amp circuit. As a result the delay caused
by the prior art output driver in series with the output of the
sense amp circuit is substantially eliminated.
[0030] FIG. 2 is a sense amp circuit 200 in accordance with one
embodiment of the present invention. Several of the components are
the same as were described in the prior art sense amp circuit 100
described in FIG. 1 above. By way of example, the NMOS 202 and PMOS
204 and 206 perform the same function as the skewed inverter 106 of
FIG. 1. Only the skewed inverter 106 (i.e. the NMOS 202 and PMOS
204) are in the data line path between input 112 and output 214. As
a result the data signal delay of the sense amp circuit 200 is
substantially less than the two-gate delay of the prior art sense
amp circuit 100.
[0031] An inverter 208 and PMOS 210 are used to provide a select
control signal sel_n to enable/disable the reset (i.e.,
discharging) of the sense amp 106. A low select control signal
sel_n is applied to the select line 216 and input t the inverter
208. The output of the inverter 208 switches high and is applied to
the gate of the PMOS 210. When the PMOS 210 is enabled, the skewed
inverter 106 can discharge when the PMOS 206 is also enabled. The
PMOS 206 is enabled when a low clk_n signal is applied to the
inverter 102. The output of the inverter 102 then switches high.
The high output of the inverter 102 is applied to the NMOS 104 and
the PMOS 206. The PMOS 206 is enabled and allows the skewed
inverter 106 to discharge through the PMOS 210 to ground. When a
high clk_n signal is applied to the inverter 102. The output of the
inverter 102 then switches low, enabling NMOS 104 to apply VDD to
pull up the data input line 112.
[0032] The NAND gate 220 has a first input coupled to the output of
the inverter 208 and a second input coupled to the output of the
inverter 222. The output of the NAND gate 220 is coupled to the
output data line 214. The input of the inverter 222 is also coupled
to the output data line 214. When the select signal enabled the
PMOS 210 to discharge the skewed inverter 106, the NAND gate 220
applies a low to the output line 214 further aiding in discharging
the skewed inverter 106. When the NAND gate 220 applies a low to
the output of the skewed inverter 106, the output of sense amp
circuit 200 can switch to a low in less time. This further reduces
the total delay required by the of sense amp circuit 200.
[0033] Because the signal throughput delay of the sense amp circuit
200 is substantially less than the two-gate delay of the prior art
sense amp circuit 100, then the sense amp circuit 200 can b used in
a variety of applications that were previously not possible. FIG. 3
is a block diagram of a pair of multiplexed sense amp circuits 302,
304, in accordance with one embodiment of the present invention.
Each of the sense amp circuits 302, 304 is substantially equivalent
to the sense amp circuit 200 shown in FIG. 2 above. The sense amp
circuits 302 and 304 are in series with a NAND gate 306. The
approximately one-gate delay of each of the sense amp circuits 302
and 304 are in series with the one-gate delay of the NAND gate 306.
As a result the overall delay of the multiplexed pair of sense amp
circuits 302 and 304 is approximately a two-gate delay which is
substantially similar to the two-gate delay of the prior art sense
amp circuit 100, as discussed above.
[0034] The pair of sense amp circuits 302 and 304 are multiplexed
by being enabled in turn via the respective sel_n signal inputs as
described above. By way of example the multiplexed pair of sense
amp circuits 302 and 304 can be used in an even-odd bit selection
system. This even-odd bit selection system effectively multiplexes
the two even-odd bit inputs rbl1_0 and rbl0_0 into a single output
data signal dout_n.
[0035] FIG. 4 is a sense amp circuit 400 in accordance with one
embodiment of the resent invention. The sense amp circuit 400 is
substantially similar to the sense amp circuit 200 described above.
One addition is a half latch circuit 402. The half latch circuit
402 includes PMS 404 and 406. PMOS 404 has a gate coupled to the
output of the sense amp circuit 400. Whenever the output of the
sense amp circuit 400 is high, the PMOS 404 can conduct. PMOS 406
has a gate coupled to the pre-charge signal such that when the pre
charge NMOS 104 is not pre-charging the input data line 112, the
half latch circuit 402 applies a low to the input data line 112.
Applying a low to the input data line 112 ensures that the input
data line 112 does not float around at a low condition but rather
is in effect latched to a low data signal level.
[0036] The pre-charge NMOS 104 and the half latch circuit 402 act
to substantially reduce any "conditional states" that may occur on
the input 112 of the sense amp circuit 400. The NAND gate 220 and
the inverter 222 act to substantially reduce any "conditional
states" that may occur on the output 214 of the sense amp circuits
200 and 400.
[0037] While the above described embodiments have been described in
terms of PMOS and NMOS devices, such that the sense amplifier
switches as the input signal passes upward through a high threshold
voltage, it should be understood that the various embodiments of
the improved sense amp circuits could also be enabled using a sense
amplifier that switches as the input signal passes downward through
a low threshold voltage.
[0038] With the above embodiments in mind, it should be understood
that the invention may employ various computer-implemented
operations involving data stored in computer systems. These
operations are those requiring physical manipulation of physical
quantities. Usually, though not necessarily, these quantities take
the form of electrical or magnetic signals capable of being stored,
transferred, combined, compared, and otherwise manipulated.
Further, the manipulations performed are often referred to in
terms, such as producing, identifying, determining, or
comparing.
[0039] Any of the operations described herein that form part of the
invention are useful machine operations. The invention also relates
to a device or an apparatus for performing these operations. The
apparatus may be specially constructed for the required purposes,
or it may be a general-purpose computer selectively activated or
configured by a computer program stored in the computer. In
particular, various general-purpose machines may be used with
computer programs written in accordance with the teachings herein,
or it may be more convenient to construct a more specialized
apparatus to perform the required operations.
[0040] Although the foregoing invention has been described in some
detail for purposes of clarity of understanding, it will be
apparent that certain changes and modifications may be practiced
within the scope of the appended claims. Accordingly, the present
embodiments are to be considered as illustrative and not
restrictive, and the invention is not to be limited to the details
given herein, but may be modified within the scope and equivalents
of the appended claims.
* * * * *