Note: The # symbol indicates signal is active LOW. A dash (–)
indicates x8 and x4 pin function is same as x16 pin function.
16 Meg x 48 Meg x 84 Meg x 16
Configuration4 Meg x 4 x 4 banks2 Meg x 8 x 4 banks1 Meg x 16 x 4 banks
Refresh Count4K4K4K
Row Addressing4K (A0-A11)4K (A0-A11)4K (A0-A11)
Bank Addressing4 (BA0, BA1)4 (BA0, BA1)4 (BA0, BA1)
Column Addressing1K (A0-A9)512 (A0-A8)256 (A0-A7)
DQ7
-
NC
DQ6
-
NC
DQ5
-
NC
DQ4
-
NC
-
-
DQM
-
-
-
-
-
-
-
-
-
-
-
NC
-
NC
DQ3
-
NC
NC
-
NC
DQ2
-
NC
-
-
DQM
-
-
-
-
-
-
-
-
-
-
-
KEY TIMING PARAMETERS
• Operating Temperature Range
Commercial (0°C to +70°C)None
Industrial (-40°C to +85°C)IT
NOTE: 1. Refer to Micron Technical Note: TN-48-05.
MT48LC16M4A2TG16 Meg x 4
MT48LC8M8A2TG8 Meg x 8
MT48LC4M16A2TG4 Meg x 16
GENERAL DESCRIPTION
The Micron® 64Mb SDRAM is a high-speed CMOS,
dynamic random-access memory containing
67,108,864 bits. It is internally configured as a quadbank DRAM with a synchronous interface (all signals
are registered on the positive edge of the clock signal,
CLK). Each of the x4’s 16,777,216-bit banks is organized as 4,096 rows by 1,024 columns by 4 bits. Each of
the x8’s 16,777,216-bit banks is organized as 4,096 rows
by 512 columns by 8 bits. Each of the x16’s 16,777,216bit banks is organized as 4,096 rows by 256 columns by
16 bits.
Read and write accesses to the SDRAM are burst
oriented; accesses start at a selected location and continue for a programmed number of locations in a programmed sequence. Accesses begin with the
registration of an ACTIVE command, which is then followed by a READ or WRITE command. The address bits
registered coincident with the ACTIVE command are
used to select the bank and row to be accessed (BA0,
BA1 select the bank; A0-A11 select the row). The ad-
dress bits registered coincident with the READ or WRITE
command are used to select the starting column location for the burst access.
The SDRAM provides for programmable READ or
WRITE burst lengths of 1, 2, 4, or 8 locations, or the
full page, with a burst terminate option. An auto
precharge function may be enabled to provide a selftimed row precharge that is initiated at the end of the
burst sequence.
The 64Mb SDRAM uses an internal pipelined
architecture to achieve high-speed operation. This
architecture is compatible with the 2n rule of prefetch
architectures, but it also allows the column address to
be changed on every clock cycle to achieve a highspeed, fully random access. Precharging one bank
while accessing one of the other three banks will hide
the precharge cycles and provide seamless, highspeed, random-access operation.
The 64Mb SDRAM is designed to operate in 3.3V
memory systems. An auto refresh mode is provided,
along with a power-saving, power-down mode.
All inputs and outputs are LVTTL-compatible.
SDRAMs offer substantial advances in DRAM operating performance, including the ability to synchronously burst data at a high data rate with automatic
column-address generation, the ability to interleave
between internal banks in order to hide precharge time
and the capability to randomly change column
addresses on each clock cycle during a burst access.
38CLKInputClock: CLK is driven by the system clock. All SDRAM input signals are
sampled on the positive edge of CLK. CLK also increments the internal
burst counter and controls the output registers.
37CKEInputClock Enable: CKE activates (HIGH) and deactivates (LOW) the CLK
signal. Deactivating the clock provides PRECHARGE POWER-DOWN
and SELF REFRESH operation (all banks idle), ACTIVE POWER-DOWN
(row active in any bank) or CLOCK SUSPEND operation (burst/access in
progress). CKE is synchronous except after the device enters powerdown and self refresh modes, where CKE becomes asynchronous until
after exiting the same mode. The input buffers, including CLK, are
disabled during power-down and self refresh modes, providing low
standby power. CKE may be tied HIGH.
19CS#InputChip Select: CS# enables (registered LOW) and disables (registered
HIGH) the command decoder. All commands are masked when CS# is
registered HIGH. CS# provides for external bank selection on systems
with multiple banks. CS# is considered part of the command code.
16, 1 7, 1 8WE#, CAS#,Input Command Inputs: WE#, CAS#, and RAS# (along with CS#) define the
RAS#command being entered.
39x4, x8: DQMInputInput/Output Mask: DQM is an input mask signal for write accesses and
an output enable signal for read accesses. Input data is masked when
15, 39x16: DQML,DQM is sampled HIGH during a WRITE cycle. The output buffers are
DQMHplaced in a High-Z state (two-clock latency) when DQM is sampled
HIGH during a READ cycle. On the x4 and x8, DQML (Pin 15) is a NC
and DQMH is DQM. On the x16, DQML corresponds to DQ0-DQ7 and
DQMH corresponds to DQ8-DQ15. DQML and DQMH are considered
same state when referenced as DQM.
20, 21BA0, BA1InputBank Address Inputs: BA0 and BA1 define to which bank the ACTIVE,
READ, WRITE or PRECHARGE command is being applied.
23-26, 29-34, 22, 35A0-A11InputAddress Inputs: A0-A11 are sampled during the ACTIVE command
(row-address A0-A11) and READ/WRITE command (column-address A0A9 [x4]; A0-A8 [x8]; A0-A7 [x16]; with A10 defining auto precharge) to
select one location out of the memory array in the respective bank.
A10 is sampled during a PRECHARGE command to determine if all
banks are to be precharged (A10[HIGH]) or bank selected by BA0,
BA1 (A1[LOW]). The address inputs also provide the op-code
during a LOAD MODE REGISTER command.
2, 4, 5, 7, 8, 10, 11, 13, 42, DQ0-DQ15 x1 6: I/O Data Input/Output: Data bus for x16 (4, 7, 10, 13, 42, 45, 48, and 51 are
44, 45, 47, 48, 50, 51, 53NCs for x8; and 2, 4, 7, 8, 10, 13, 42, 45, 47, 48, 51, and 53 are NCs for x4).
2, 5, 8, 11, 44, 47, 50, 53DQ0-DQ7x8: I/O Data Input/Output: Data bus for x8 (2, 8, 47, 53 are NCs for x4).
5, 11, 44, 50DQ0-DQ3x4: I/O Data Input/Output: Data bus for x4.
40NC–No Connect: These pins should be left unconnected.
36NC–Address input (A12) for the 256Mb and 512Mb devices
3, 9, 43, 49VDDQSupply DQ Power: Isolated DQ power on the die for improved noise immunity.
6, 12, 46, 52VSSQSupply DQ Ground: Isolated DQ ground on the die for improved noise
In general, the 64Mb SDRAMs (4 Meg x 4 x 4 banks,
2 Meg x 8 x 4 banks and 1 Meg x 16 x 4 banks) are quadbank DRAMs which operate at 3.3V and include a synchronous interface (all signals are registered on the
positive edge of the clock signal, CLK). Each of the x4’s
16,777,216-bit banks is organized as 4,096 rows by 1,024
columns by 4 bits. Each of the x8’s 16,777,216-bit banks
is organized as 4,096 rows by 512 columns by 8 bits.
Each of the x16’s 16,777,216-bit banks is organized as
4,096 rows by 256 columns by 16 bits.
Read and write accesses to the SDRAM are burst
oriented; accesses start at a selected location and continue for a programmed number of locations in a programmed sequence. Accesses begin with the registration of an ACTIVE command which is then followed by
a READ or WRITE command. The address bits registered coincident with the ACTIVE command are used
to select the bank and row to be accessed (BA0 and BA1
select the bank, A0-A11 select the row). The address
bits (x4: A0-A9; x8: A0-A8; x16: A0-A7) registered coincident with the READ or WRITE command are used to
select the starting column location for the burst access.
Prior to normal operation, the SDRAM must be initialized. The following sections provide detailed information covering device initialization, register definition, command descriptions and device operation.
Initialization
SDRAMs must be powered up and initialized in a
predefined manner. Operational procedures other
than those specified may result in undefined operation. Once power is applied to VDD and VDDQ (simultaneously) and the clock is stable (stable clock is defined
as a signal cycling within timing constraints specified
for the clock pin), the SDRAM requires a 100µs delay
prior to issuing any command other than a COMMAND
INHIBIT or a NOP. Starting at some point during this
100µs period and continuing at least through the end
of this period, COMMAND INHIBIT or NOP commands
should be applied.
Once the 100µs delay has been satisfied with at
least one COMMAND INHIBIT or NOP command having been applied, a PRECHARGE command should be
applied. All banks must be precharged, thereby placing the device in the all banks idle state.
Once in the idle state, two AUTO REFRESH cycles
must be performed. After the AUTO REFRESH cycles
are complete, the SDRAM is ready for mode register
programming. Because the mode register will power
up in an unknown state, it should be loaded prior to
applying any operational command.
Register Definition
MODE REGISTER
The mode register is used to define the specific mode
of operation of the SDRAM. This definition includes
the selection of a burst length, a burst type, a CAS
latency, an operating mode and a write burst mode, as
shown in Figure 1. The mode register is programmed
via the LOAD MODE REGISTER command and will retain the stored information until it is programmed again
or the device loses power.
Mode register bits M0-M2 specify the burst length,
M3 specifies the type of burst (sequential or interleaved), M4-M6 specify the CAS latency, M7 and M8
specify the operating mode, M9 specifies the WRITE
burst mode, and M10 and M11 are reserved for future
use.
The mode register must be loaded when all banks
are idle, and the controller must wait the specified time
before initiating the subsequent operation. Violating
either of these requirements will result in unspecified
operation.
Burst Length
Read and write accesses to the SDRAM are burst
oriented, with the burst length being programmable,
as shown in Figure 1. The burst length determines the
maximum number of column locations that can be accessed for a given READ or WRITE command. Burst
lengths of 1, 2, 4, or 8 locations are available for both the
sequential and the interleaved burst types, and a fullpage burst is available for the sequential type. The
full-page burst is used in conjunction with the BURST
TERMINATE command to generate arbitrary burst
lengths.
Reserved states should not be used, as unknown
operation or incompatibility with future versions may
result.
When a READ or WRITE command is issued, a block
of columns equal to the burst length is effectively selected. All accesses for that burst take place within this
block, meaning that the burst will wrap within the block
if a boundary is reached. The block is uniquely selected by A1-A9 (x4), A1-A8 (x8) or A1-A7 (x16) when the
burst length is set to two; by A2-A9 (x4), A2-A8 (x8) or
A2-A7 (x16) when the burst length is set to four; and by
A3-A9 (x4), A3-A8 (x8) or A3-A7 (x16) when the burst
length is set to eight. The remaining (least significant)
address bit(s) is (are) used to select the starting location within the block. Full-page bursts wrap within the
page if the boundary is reached.
Accesses within a given burst may be programmed
to be either sequential or interleaved; this is referred to
as the burst type and is selected via bit M3.
The ordering of accesses within a burst is determined by the burst length, the burst type and the starting column address, as shown in Table 1.
Figure 1
Mode Register Definition
A11
11
Reserved* WB
*Should program
M11, M10 = “0, 0”
to ensure compatibility
with future devices.
A10
A9
9
10
Op Mode
A6 A5 A4
A7
654
7
M7
M8
0-0-Defined
A3A8A2A1A0
382
Burst LengthCAS Latency BT
M1
M2
0
0
0
0
1
0
1
0
0
1
0
1
1
1
1
1
M3
0
1
M5
M6
0
0
0
0
1
0
1
0
0
1
0
1
1
1
1
1
M6-M0
-
Address Bus
1
0
Mode Register (Mx)
Burst Length
M0
M3 = 0
0
1
1
2
0
4
1
8
0
Reserved
1
Reserved
0
Reserved
1
Full Page
Burst Type
Sequential
Interleaved
M4
0
1
0
1
0
1
0
1
Operating Mode
Standard Operation
All other states reserved
CAS Latency
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
M3 = 1
1
2
4
8
Reserved
Reserved
Reserved
Reserved
2
3
Table 1
Burst Definition
BurstStarting ColumnOrder of Accesses Within a Burst
NOTE: 1. For full-page accesses: y = 1,024 (x4); y = 512 (x8);
y = 256 (x16).
2. For a burst length of two, A1-A9 (x4), A1-A8 (x8),
or A1-A7 (x16) select the block-of-two burst; A0
selects the starting column within the block.
3. For a burst length of four, A2-A9 (x4), A2-A8 (x8),
or A2-A7 (x16) select the block-of-four burst; A0A1 select the starting column within the block.
4. For a burst length of eight, A3-A9 (x4), A3-A8 (x8),
or A3-A7 (x16) select the block-of-eight burst; A0A2 select the starting column within the block.
5. For a full-page burst, the full row is selected and
A0-A9 (x4), A0-A8 (x8), or A0-A7 (x16) select the
starting column.
6. Whenever a boundary of the block is reached
within a given sequence above, the following
access wraps within the block.
7. For a burst length of one, A0-A9 (x4), A0-A8 (x8),
or A0-A7 (x16) select the unique column to be
accessed, and mode register bit M3 is ignored.
The CAS latency is the delay, in clock cycles, between the registration of a READ command and the
availability of the first piece of output data. The latency can be set to two or three clocks.
If a READ command is registered at clock edge n,
and the latency is m clocks, the data will be available by
clock edge n + m. The DQs will start driving as a result of
the clock edge one cycle earlier (n + m - 1), and provided
that the relevant access times are met, the data will be
valid by clock edge n + m. For example, assuming that
the clock cycle time is such that all relevant access times
are met, if a READ command is registered at T0 and the
latency is programmed to two clocks, the DQs will start
driving after T1 and the data will be valid by T2, as
shown in Figure 2. Table 2 indicates the operating frequencies at which each CAS latency setting can be used.
Reserved states should not be used as unknown
operation or incompatibility with future versions
may result.
Figure 2
CAS Latency
T2T1T3T0
CLK
COMMAND
DQ
NOPREAD
t
LZ
t
AC
NOP
t
OH
D
OUT
Operating Mode
The normal operating mode is selected by setting
M7 and M8 to zero; the other combinations of values for
M7 and M8 are reserved for future use and/or test
modes. The programmed burst length applies to both
READ and WRITE bursts.
Test modes and reserved states should not be used
because unknown operation or incompatibility with
future versions may result.
Write Burst Mode
When M9 = 0, the burst length programmed via
M0-M2 applies to both READ and WRITE bursts; when
M9 = 1, the programmed burst length applies to
READ bursts, but write accesses are single-location
(nonburst) accesses.
Truth Table 1 provides a quick reference of
available commands. This is followed by a written description of each command. Three additional Truth
TRUTH TABLE 1 – COMMANDS AND DQM OPERATION
(Note: 1)
NAME (FUNCTION)CS# RAS# CAS# WE# DQMADDRDQs NOTES
COMMAND INHIBIT (NOP)HXXXXXX
NO OPERATION (NOP)LHHHXXX
ACTIVE (Select bank and activate row)LLHHXBank/RowX3
READ (Select bank and column, and start READ burst)LHLHL/H8Bank/ColX4
WRITE (Select bank and column, and start WRITE burst)LHLLL/H8Bank/ColValid4
BURST TERMINATELHHLXXActive
PRECHARGE (Deactivate row in bank or banks)LLHLXCodeX5
AUTO REFRESH or SELF REFRESHLLLHXXX6, 7
Tables appear following the Operation section; these
tables provide current state/next state information.
NOTE: 1. CKE is HIGH for all commands shown except SELF REFRESH.
2. A0-A11 define the op-code written to the mode register.
3. A0-A11 provide row address, and BA0, BA1 determine which bank is made active.
4. A0-A9 (x4), A0-A8 (x8), or A0-A7 (x16) provide column address; A10 (HIGH) enables the auto precharge feature
(nonpersistent), while A10 (LOW) disables the auto precharge feature; BA0, BA1 determine which bank is being read
from or written to.
5. A10 (LOW): BA0, BA1 determine the bank being precharged. A10 HIGH: All banks precharged and BA0, BA1 are “Don’t
Care.”
6. This command is AUTO REFRESH if CKE is (HIGH), SELF REFRESH if CKE is LOW.
7. Internal refresh counter controls row addressing; all inputs and I/Os are “Don’t Care” except for CKE.
8. Activates or deactivates the DQs during WRITEs (zero-clock delay) and READs (two-clock delay).
The COMMAND INHIBIT function prevents new
commands from being executed by the SDRAM, regardless of whether the CLK signal is enabled. The
SDRAM is effectively deselected. Operations already
in progress are not affected.
NO OPERATION (NOP)
The NO OPERATION (NOP) command is used to
perform a NOP to an SDRAM which is selected (CS# is
LOW). This prevents unwanted commands from being
registered during idle or wait states. Operations already
in progress are not affected.
LOAD MODE REGISTER
The mode register is loaded via inputs A0-A11. See
mode register heading in the Register Definition section.
The LOAD MODE REGISTER command can only be issued when all banks are idle, and a subsequent executable command cannot be issued until tMRD is met.
ACTIVE
The ACTIVE command is used to open (or activate)
a row in a particular bank for a subsequent access. The
value on the BA0, BA1 inputs selects the bank, and the
address provided on inputs A0-A11 selects the row.
This row remains active (or open) for accesses until a
PRECHARGE command is issued to that bank.
A PRECHARGE command must be issued before opening a different row in the same bank.
READ
The READ command is used to initiate a burst read
access to an active row. The value on the BA0, BA1
inputs selects the bank, and the address provided on
inputs A0-A9 (x4), A0-A8 (x8), or A0-A7 (x16) selects the
starting column location. The value on input A10 determines whether or not auto precharge is used. If auto
precharge is selected, the row being accessed will be
precharged at the end of the READ burst; if auto
precharge is not selected, the row will remain open for
subsequent accesses. Read data appears on the DQs
subject to the logic level on the DQM inputs two clocks
earlier. If a given DQM signal was registered HIGH, the
corresponding DQs will be High-Z two clocks later; if
the DQM signal was registered LOW, the DQs will provide valid data.
64Mb: x4, x8, x16
SDRAM
precharge is selected, the row being accessed will be
precharged at the end of the WRITE burst; if auto
precharge is not selected, the row will remain open for
subsequent accesses. Input data appearing on the DQs
is written to the memory array subject to the DQM input logic level appearing coincident with the data. If a
given DQM signal is registered LOW, the corresponding data will be written to memory; if the DQM signal is
registered HIGH, the corresponding data inputs will
be ignored, and a WRITE will not be executed to that
byte/column location.
PRECHARGE
The PRECHARGE command is used to deactivate
the open row in a particular bank or the open row in all
banks. The bank(s) will be available for a subsequent
row access a specified time (tRP) after the PRECHARGE
command is issued. Input A10 determines whether
one or all banks are to be precharged, and in the case
where only one bank is to be precharged, inputs BA0,
BA1 select the bank. Otherwise BA0, BA1 are treated as
“Don’t Care.” Once a bank has been precharged, it is in
the idle state and must be activated prior to any READ
or WRITE commands being issued to that bank.
AUTO PRECHARGE
Auto precharge is a feature which performs the
same individual-bank PRECHARGE function described above, without requiring an explicit command.
This is accomplished by using A10 to enable auto
precharge in conjunction with a specific READ or WRITE
command. A precharge of the bank/row that is addressed with the READ or WRITE command is automatically performed upon completion of the READ or
WRITE burst, except in the full-page burst mode, where
auto precharge does not apply. Auto precharge is nonpersistent in that it is either enabled or disabled for
each individual READ or WRITE command.
Auto precharge ensures that the precharge is initiated at the earliest valid stage within a burst. The user
must not issue another command to the same bank
until the precharge time (tRP) is completed. This is
determined as if an explicit PRECHARGE command
was issued at the earliest possible time, as described
for each burst type in the Operation section of this data
sheet.
WRITE
The WRITE command is used to initiate a burst write
access to an active row. The value on the BA0, BA1
inputs selects the bank, and the address provided on
inputs A0-A9 (x4), A0-A8 (x8), or A0-A7 (x16) selects the
starting column location. The value on input A10 determines whether or not auto precharge is used. If auto
The BURST TERMINATE command is used to truncate either fixed-length or full-page bursts. The most
recently registered READ or WRITE command prior to
the BURST TERMINATE command will be truncated,
as shown in the Operation section of this data sheet.
12
Page 13
AUTO REFRESH
www.DataSheet4U.com
AUTO REFRESH is used during normal operation of
the SDRAM and is analagous to CAS#-BEFORE-RAS#
(CBR) REFRESH in conventional DRAMs. This command is nonpersistent, so it must be issued each time
a refresh is required. All active banks must be
PRECHARGED prior to issuing an AUTO REFRESH command. The AUTO REFRESH command should not be
issued until the minimum tRP has been met after the
PRECHARGE command as shown in the operation section.
The addressing is generated by the internal refresh
controller. This makes the address bits “Don’t Care”
during an AUTO REFRESH command. The 64Mb
SDRAM requires 4,096 AUTO REFRESH cycles every
64ms (tREF), regardless of width option. Providing a
distributed AUTO REFRESH command every 15.625µs
will meet the refresh requirement and ensure that each
row is refreshed. Alternatively, 4,096 AUTO REFRESH
commands can be issued in a burst at the minimum
cycle rate (tRC), once every 64ms.
SELF REFRESH
The SELF REFRESH command can be used to retain
data in the SDRAM, even if the rest of the system is
powered down. When in the self refresh mode, the
64Mb: x4, x8, x16
SDRAM
SDRAM retains data without external clocking.
The SELF REFRESH command is initiated like an AUTO
REFRESH command except CKE is disabled (LOW).
Once the SELF REFRESH command is registered, all
the inputs to the SDRAM become “Don’t Care,” with
the exception of CKE, which must remain LOW.
Once self refresh mode is engaged, the SDRAM provides its own internal clocking, causing it to perform its
own AUTO REFRESH cycles. The SDRAM must remain
in self refresh mode for a minimum period equal to
t
RAS and may remain in self refresh mode for an indefi-
nite period beyond that.
The procedure for exiting self refresh requires a sequence of commands. First, CLK must be stable (stable
clock is defined as a signal cycling within timing constraints specified for the clock pin) prior to CKE going
back HIGH. Once CKE is HIGH, the SDRAM must have
NOP commands issued (a minimum of two clocks) for
t
XSR, because time is required for the completion of
any internal refresh in progress.
Upon exiting the self refresh mode, AUTO REFRESH
commands must be issued every 15.625µs or less as
both SELF REFRESH and AUTO REFRESH utilize the
row refresh counter.
Before any READ or WRITE commands can be issued to a bank within the SDRAM, a row in that bank
must be “opened.” This is accomplished via the ACTIVE command, which selects both the bank and the
row to be activated (see Figure 3).
After opening a row (issuing an ACTIVE command),
a READ or WRITE command may be issued to that row,
subject to the tRCD specification. tRCD (MIN) should
be divided by the clock period and rounded up to the
next whole number to determine the earliest clock edge
after the ACTIVE command on which a READ or WRITE
command can be entered. For example, a tRCD specification of 20ns with a 125 MHz clock (8ns period) results
in 2.5 clocks, rounded to 3. This is reflected in Figure 4,
which covers any case where 2 < tRCD (MIN)/tCK £ 3.
(The same procedure is used to convert other specification limits from time units to clock cycles).
A subsequent ACTIVE command to a different row
in the same bank can only be issued after the previous
active row has been “closed” (precharged). The minimum time interval between successive ACTIVE commands to the same bank is defined by tRC.
A subsequent ACTIVE command to another bank
can be issued while the first bank is being accessed,
which results in a reduction of total row-access overhead. The minimum time interval between successive
ACTIVE commands to different banks is defined by
READ bursts are initiated with a READ command,
as shown in Figure 5.
The starting column and bank addresses are provided with the READ command, and auto precharge is
either enabled or disabled for that burst access. If auto
precharge is enabled, the row being accessed is
precharged at the completion of the burst. For the generic READ commands used in the following illustrations, auto precharge is disabled.
During READ bursts, the valid data-out element
from the starting column address will be available following the CAS latency after the READ command. Each
subsequent data-out element will be valid by the next
positive clock edge. Figure 6 shows general timing for
each possible CAS latency setting.
64Mb: x4, x8, x16
SDRAM
Upon completion of a burst, assuming no other commands have been initiated, the DQs will go High-Z. A
full-page burst will continue until terminated. (At the
end of the page, it will wrap to column 0 and continue.)
Data from any READ burst may be truncated with a
subsequent READ command, and data from a fixedlength READ burst may be immediately followed by
data from a READ command. In either case, a continuous flow of data can be maintained. The first data element from the new burst follows either the last element of a completed burst or the last desired data element of a longer burst which is being truncated.
The new READ command should be issued x cycles
before the clock edge at which the last desired data
element is valid, where x equals the CAS latency minus
one. This is shown in Figure 7 for CAS latencies of two
and three; data element n + 3 is either the last of a burst
of four or the last desired of a longer burst. The 64Mb
SDRAM uses a pipelined architecture and therefore
Figure 7
Consecutive READ Bursts
T2T1T4T3T6T5T0
CLK
COMMAND
ADDRESS
DQ
READNOPNOPNOPNOP
BANK,
COL n
NOP
D
OUT
n
does not require the 2n rule associated with a prefetch
architecture. A READ command can be initiated on any
clock cycle following a previous READ command. Fullspeed random read accesses can be performed to the
same bank, as shown in Figure 8, or each subsequent
READ may be performed to a different bank.
READ
X = 1 cycle
BANK,
COL b
D
D
OUT
n + 1
OUT
n + 2
OUT
D
n + 3
D
OUT
b
CAS Latency = 2
T2T1T4T3T6T5T0
CLK
COMMAND
ADDRESS
DQ
READNOPNOPNOPNOP
BANK,
COL n
CAS Latency = 3
NOP
D
OUT
n
NOTE: Each READ command may be to any bank. DQM is LOW.
NOTE: Each READ command may be to any bank. DQM is LOW.
17
DON’T CARE
Page 18
64Mb: x4, x8, x16
DON’T CARE
READNOPNOPNOPNOP
DQM
CLK
DQ
D
OUT
n
T2T1T4T3T0
COMMAND
ADDRESS
BANK,
COL n
WRITE
DIN b
BANK,
COL b
T5
DS
t
HZ
t
NOTE:A CAS latency of three is used for illustration. The
READ command
may be to any bank, and the WRITE command may be to any bank.
TRANSITIONING DATA
www.DataSheet4U.com
SDRAM
Data from any READ burst may be truncated with a
subsequent WRITE command, and data from a fixedlength READ burst may be immediately followed by
data from a WRITE command (subject to bus turnaround limitations). The WRITE burst may be initiated
on the clock edge immediately following the last (or last
desired) data element from the READ burst, provided
that I/O contention can be avoided. In a given system
design, there may be a possibility that the device driving the input data will go Low-Z before the SDRAM DQs
go High-Z. In this case, at least a single-cycle delay
should occur between the last read data and the WRITE
command.
The DQM input is used to avoid I/O contention, as
shown in Figures 9 and 10. The DQM signal must be
asserted (HIGH) at least two clocks prior to the WRITE
command (DQM latency is two clocks for output
Figure 9
READ to WRITE
T2T1T4T3T0
CLK
buffers) to suppress data-out from the READ. Once the
WRITE command is registered, the DQs will go High-Z
(or remain High-Z), regardless of the state of the DQM
signal, provided the DQM was active on the clock just
prior to the WRITE command that truncated the READ
command. If not, the second WRITE will be an invalid
WRITE. For example, if DQM was LOW during T4 in
Figure 10, then the WRITEs at T5 and T7 would be
valid, while the WRITE at T6 would be invalid.
The DQM signal must be de-asserted prior to the
WRITE command (DQM latency is zero clocks for input
buffers) to ensure that the written data is not masked.
Figure 9 shows the case where the clock frequency allows for bus contention to be avoided without adding a
NOP cycle, and Figure 10 shows the case where the
additional NOP is needed.
Figure 10
READ to WRITE With
Extra Clock Cycle
DQM
COMMAND
ADDRESS
NOTE: A CAS latency of three is used for illustration. The
command may be to any bank, and the WRITE command
may be to any bank. If a burst of one is used, then DQM is
not required.
NOP
t
CK
t
HZ
D
OUT
n
DON’T CARE
WRITE
BANK,
COL b
DIN b
t
DS
READ
18
Page 19
64Mb: x4, x8, x16
www.DataSheet4U.com
SDRAM
A fixed-length READ burst may be followed by, or
truncated with, a PRECHARGE command to the same
bank (provided that auto precharge was not activated), and a full-page burst may be truncated with a
PRECHARGE command to the same bank. The
PRECHARGE command should be issued x cycles before the clock edge at which the last desired data element is valid, where x equals the CAS latency minus
one. This is shown in Figure 11 for each possible CAS
latency; data element n + 3 is either the last of a burst of
Figure 11
READ to PRECHARGE
T2T1T4T3T6T5T0
CLK
COMMAND
ADDRESS
READNOPNOPNOPNOPNOP
BANK a,
COL n
four or the last desired of a longer burst. Following the
PRECHARGE command, a subsequent command to
the same bank cannot be issued until tRP is met. Note
that part of the row precharge time is hidden during
the access of the last data element(s).
In the case of a fixed-length burst being executed to
completion, a PRECHARGE command issued at the
optimum time (as described above) provides the same
operation that would result from the same fixed-length
burst with auto precharge. The disadvantage of the
PRECHARGE command is that it requires that the command and address buses be available at the appropriate time to issue the command; the advantage of the
PRECHARGE command is that it can be used to truncate fixed-length or full-page bursts.
Full-page READ bursts can be truncated with the
BURST TERMINATE command, and fixed-length READ
bursts may be truncated with a BURST TERMINATE
Figure 12
Terminating a READ Burst
T2T1T4T3T6T5T0
CLK
COMMAND
ADDRESS
READNOPNOPNOP
BANK,
COL n
NOP
command, provided that auto precharge was not activated. The BURST TERMINATE command should be
issued x cycles before the clock edge at which the last
desired data element is valid, where x equals the CAS
latency minus one. This is shown in Figure 12 for each
possible CAS latency; data element n + 3 is the last
desired data element of a longer burst.
WRITE bursts are initiated with a WRITE command,
as shown in Figure 13.
The starting column and bank addresses are
provided with the WRITE command, and auto
precharge is either enabled or disabled for that access.
If auto precharge is enabled, the row being accessed is
precharged at the completion of the burst. For the generic WRITE commands used in the following illustrations, auto precharge is disabled.
During WRITE bursts, the first valid data-in element will be registered coincident with the WRITE command. Subsequent data elements will be registered on
each successive positive clock edge. Upon completion
of a fixed-length burst, assuming no other commands
have been initiated, the DQs will remain High-Z and
any additional input data will be ignored (see Figure
14). A full-page burst will continue until terminated.
(At the end of the page, it will wrap to column 0 and
continue.)
Data for any WRITE burst may be truncated with a
subsequent WRITE command, and data for a fixedlength WRITE burst may be immediately followed by
data for a WRITE command. The new WRITE command
can be issued on any clock following the previous WRITE
command, and the data provided coincident with the
new command applies to the new command.
64Mb: x4, x8, x16
SDRAM
An example is shown in Figure 15. Data n + 1 is either
the last of a burst of two or the last desired of a longer
burst. The 64Mb SDRAM uses a pipelined architecture
and therefore does not require the 2n rule associated
with a prefetch architecture. A WRITE command can
be initiated on any clock cycle following a previous
WRITE command. Full-speed random write accesses
within a page can be performed to the same bank, as
shown in Figure 16, or each subsequent WRITE may be
performed to a different bank.
subsequent READ command, and data for a fixedlength WRITE burst may be immediately followed by a
subsequent READ command. Once the READ command is registered, the data inputs will be ignored, and
WRITEs will not be executed. An example is shown in
Figure 17. Data n + 1 is either the last of a burst of two or
the last desired of a longer burst.
Data for a fixed-length WRITE burst may be followed by, or truncated with, a PRECHARGE command
to the same bank (provided that auto precharge was
not activated), and a full-page WRITE burst may be
truncated with a PRECHARGE command to the same
bank. The PRECHARGE command should be issued
Figure 16
Random WRITE Cycles
T2T1T3T0
CLK
64Mb: x4, x8, x16
SDRAM
t
WR after the clock edge at which the last desired input
data element is registered. The auto precharge mode
requires a tWR of at least one clock plus time, regardless
of frequency. In addition, when truncating a WRITE
burst, the DQM signal must be used to mask input data
for the clock edge prior to, and the clock edge coincident with, the PRECHARGE command. An example is
shown in Figure 18. Data n + 1 is either the last of a burst
of two or the last desired of a longer burst. Following the
PRECHARGE command, a subsequent command to
the same bank cannot be issued until
In the case of a fixed-length burst being executed to
completion, a PRECHARGE command issued at the
optimum time (as described above) provides the same
operation that would result from the same fixed-length
burst with auto precharge. The disadvantage of the
PRECHARGE command is that it requires that the command and address buses be available at the appropriate time to issue the command; the advantage of the
PRECHARGE command is that it can be used to truncate fixed-length or full-page bursts.
t
RP is met.
CLK
COMMAND
ADDRESS
DQ
COMMAND
ADDRESS
DQ
BANK,
COL n
D
IN
n
WRITE
BANK,
COL n
D
IN
n
WRITE
BANK,
COL a
D
IN
a
WRITEWRITE
BANK,
COL x
IN
D
x
TRANSITIONING DATA
Figure 17
WRITE to READ
T2T1T3T0
NOPWRITE
D
n + 1
READNOPNOP
BANK,
COL b
IN
TRANSITIONING DATA
BANK,
COL m
IN
D
m
DON’T CARE
T4T5
NOP
D
OUT
b
DON’T CARE
OUT
D
b + 1
Figure 18
WRITE to PRECHARGE
T2T1T4T3T0
CLK
t
WR @ tCLK ≥ 15ns
DQM
t
RP
NOPWRITE
n + 1
NOPWRITE
n + 1
PRECHARGE
BANK
(a or all)
t
WR
D
IN
NOP
PRECHARGE
BANK
(a or all)
t
D
IN
WR
TRANSITIONING DATA
COMMAND
DQ
DQM
DQ
BANK a,
COL n
D
IN
n
BANK a,
COL n
D
IN
n
ADDRESS
t
WR = tCLK < 15ns
COMMAND
ADDRESS
NOTE: DQM could remain LOW in this example if the WRITE burst is a fixed length of two.
Fixed-length or full-page WRITE bursts can be truncated with the BURST TERMINATE command. When
truncating a WRITE burst, the input data applied coincident with the BURST TERMINATE command will be
ignored. The last data written (provided that DQM is
LOW at that time) will be the input data applied one
clock previous to the BURST TERMINATE command.
This is shown in Figure 19, where data n is the last
desired data element of a longer burst.
Figure 19
Terminating a WRITE Burst
T2T1T0
CLK
COMMAND
ADDRESS
NOTE: DQMs are LOW.
WRITE
BANK,
COL n
DQ
TRANSITIONING DATA
BURST
TERMINATE
DIN
n
NEXT
COMMAND
(ADDRESS)
(DATA)
DON’T CARE
Figure 20
PRECHARGE Command
PRECHARGE
The PRECHARGE command (Figure 20) is used to
deactivate the open row in a particular bank or the
open row in all banks. The bank(s) will be available for
t
a subsequent row access some specified time (
RP) after the PRECHARGE command is issued. Input A10
determines whether one or all banks are to be
precharged, and in the case where only one bank is to
be precharged, inputs BA0, BA1 select the bank. When
all banks are to be precharged, inputs BA0, BA1 are
treated as “Don’t Care.” Once a bank has been
precharged, it is in the idle state and must be activated
prior to any READ or WRITE commands being issued to
that bank.
POWER-DOWN
Power-down occurs if CKE is registered LOW coincident with a NOP or COMMAND INHIBIT when no accesses are in progress. If power-down occurs when all
banks are idle, this mode is referred to as precharge
power-down; if power-down occurs when there is a row
active in any bank, this mode is referred to as active
power-down. Entering power-down deactivates the input and output buffers, excluding CKE, for maximum
power savings while in standby. The device may not
remain in the power-down state longer than the refresh period (64ms) since no refresh operations are
performed in this mode.
The power-down state is exited by registering a NOP
or COMMAND INHIBIT and CKE HIGH at the desired
clock edge (meeting
NOTE: For this example, CAS latency = 2, burst length = 4 or greater, and
DQM is LOW.
CKE
INTERNAL
CLOCK
NOP
TRANSITIONING DATA
www.DataSheet4U.com
The clock suspend mode occurs when a column access/burst is in progress and CKE is registered LOW. In
the clock suspend mode, the internal clock is deactivated, “freezing” the synchronous logic.
For each positive clock edge on which CKE is
sampled LOW, the next internal positive clock edge is
suspended. Any command or data present on the input pins at the time of a suspended internal clock edge
is ignored; any data present on the DQ pins remains
driven; and burst counters are not incremented, as
long as the clock is suspended. (See examples in
Figures 22 and 23.)
64Mb: x4, x8, x16
SDRAM
Clock suspend mode is exited by registering CKE
HIGH; the internal clock and related operation will resume on the subsequent positive clock edge.
BURST READ/SINGLE WRITE
The burst read/single write mode is entered by programming the write burst mode bit (M9) in the mode
register to a logic 1. In this mode, all WRITE commands
result in the access of a single column location (burst of
one), regardless of the programmed burst length. READ
commands access columns according to the programmed burst length and sequence, just as in the
normal mode of operation (M9 = 0).
An access command (READ or WRITE) to another
bank while an access command with auto precharge
enabled is executing is not allowed by SDRAMs, unless
the SDRAM supports CONCURRENT AUTO
PRECHARGE. Micron SDRAMs support CONCURRENT
AUTO PRECHARGE. Four cases where CONCURRENT
AUTO PRECHARGE occurs are defined below.
READ with Auto Precharge
1. Interrupted by a READ (with or without auto
precharge): A READ to bank m will interrupt a READ
Figure 24
READ With Auto Precharge Interrupted by a READ
64Mb: x4, x8, x16
SDRAM
on bank n, CAS latency later. The PRECHARGE to
bank n will begin when the READ to bank m is registered (Figure 24).
2. Interrupted by a WRITE (with or without auto
precharge): A WRITE to bank m will interrupt a READ
on bank n when registered. DQM should be used
two clocks prior to the WRITE command to prevent
bus contention. The PRECHARGE to bank n will
begin when the WRITE to bank m is registered
(Figure 25).
T2T1T4T3T6T5T0
T7
CLK
COMMAND
Internal
States
ADDRESS
NOTE: DQM is LOW.
BANK n
BANK m
DQ
READ - AP
BANK n
Page ActiveREAD with Burst of 4Interrupt Burst, Precharge
3. Interrupted by a READ (with or without auto
precharge): A READ to bank m will interrupt a WRITE
on bank n when registered, with the data-out appearing CAS latency later. The PRECHARGE to bank n will
begin after tWR is met, where tWR begins when the
READ to bank m is registered. The last valid WRITE to
bank n will be data-in register ed one clock prior to the
READ to bank m (Figure 26).
Figure 26
WRITE With Auto Precharge Interrupted by a READ
T2T1T4T3T6T5T0
CLK
64Mb: x4, x8, x16
SDRAM
4. Interrupted by a WRITE (with or without auto
precharge): A WRITE to bank m will interrupt a WRITE
on bank n when registered. The PRECHARGE to bank
n will begin after
the WRITE to bank m is registered. The last valid data
WRITE to bank n will be data registered one clock prior
to a WRITE to bank m (Figure 27).
t
WR is met, where tWR begins when
T7
COMMAND
Internal
States
NOTE: 1. DQM is LOW.
BANK n
BANK m
ADDRESS
DQ
WRITE - AP
BANK n
Page ActiveWRITE with Burst of 4Interrupt Burst, Write-Back Precharge
Page ActiveREAD with Burst of 4
BANK n,
COL a
D
IN
a
a + 1
READ - AP
BANK m
t
WR - BANK n
BANK m,
COL d
D
IN
CAS Latency = 3 (BANK m)
NOPNOPNOPNOP
t
RP - BANK n
NOPNOP
D
TRANSITIONING DATA
Figure 27
WRITE With Auto Precharge Interrupted by a WRITE
T2T1T4T3T6T5T0
CLK
Internal
States
COMMAND
BANK n
BANK m
WRITE - AP
BANK n
Page ActiveWRITE with Burst of 4Interrupt Burst, Write-Back Precharge
LHPower-DownCOMMAND INHIBIT or NOPExit Power-Down5
Self RefreshCOMMAND INHIBIT or NOPExit Self Refresh6
Clock SuspendXExit Clock Suspend7
HLAll Banks IdleCOMMAND INHIBIT or NOPPower-Down Entry
All Banks IdleAUTO REFRESHSelf Refresh Entry
Reading or WritingVALIDClock Suspend Entry
HHSee Truth Table 3
NOTE: 1. CKEn is the logic state of CKE at clock edge n; CKE
2. Current state is the state of the SDRAM immediately prior to clock edge n.
3. COMMANDn is the command registered at clock edge n, and ACTIONn is a result of COMMANDn.
4. All states and sequences not shown are illegal or reserved.
5. Exiting power-down at clock edge n will put the device in the all banks idle state in time for clock edge n + 1 (provided
that tCKS is met).
6. Exiting self refresh at clock edge n will put the device in the all banks idle state once tXSR is met. COMMAND INHIBIT
or NOP commands should be issued on any clock edges occurring during the tXSR period. A minimum of two NOP
commands must be provided during tXSR period.
7. After exiting clock suspend at clock edge n, the device will resume operation and recognize the next command at clock
edge n + 1.
2. This table is bank-specific, except where noted; i.e., the current state is for a specific bank and the commands shown
are those allowed to be issued to that bank when in that state. Exceptions are covered in the notes below.
3. Current state definitions:
Idle: The bank has been precharged, and tRP has been met.
Row Active: A row in the bank has been activated, and tRCD has been met. No data bursts/accesses and
Re a d : A READ burst has been initiated, with auto precharge disabled, and has not yet terminated
Write: A WR ITE burst has been initiated, with auto precharge disabled, and has not yet termi-
4. The following states must not be interrupted by a command issued to the same bank. COMMAND INHIBIT or NOP
commands, or allowable commands to the other bank should be issued on any clock edge occurring during these states.
Allowable commands to the other bank are determined by its current state and Truth Table 3, and according to Truth
Table 4.
Precharging: Starts with registration of a PRECHARGE command and ends when tRP is met. Once tRP is
Row Activating: Starts with registration of an ACTIVE command and ends when tRCD is met. Once tRCD is
Read w/Auto
Precharge Enabled: Starts with registration of a READ command with auto precharge enabled and ends when
Write w/Auto
Precharge Enabled: Starts with registration of a WRITE command with auto precharge enabled and ends when
was HIGH and CKEn is HIGH (see Truth Table 2) and after tXSR has been
n-1
no register accesses are in progress.
or been terminated.
nated or been terminated.
met, the bank will be in the idle state.
met, the bank will be in the row active state.
t
RP has been met. Once tRP is met, the bank will be in the idle state.
t
RP has been met. Once tRP is met, the bank will be in the idle state.
5. The following states must not be interrupted by any executable command; COMMAND INHIBIT or NOP commands must
be applied on each positive clock edge during these states.
Refreshing: Starts with registration of an AUTO REFRESH command and ends when
is met, the SDRAM will be in the all banks idle state.
Accessing Mode
Register: Starts with registration of a LOAD MODE REGISTER command and ends when
been met. Once
Precharging All: Starts with registration of a PRECHARGE ALL command and ends when tRP is met. Once tRP
is met, all banks will be in the idle state.
6. All states and sequences not shown are illegal or reserved.
7. Not bank-specific; requires that all banks are idle.
8. May or may not be bank-specific; if all banks are to be precharged, all must be in a valid state for precharging.
9. Not bank-specific; BURST TERMINATE affects the most recent READ or WRITE burst, regardless of bank.
10. READs or WRITEs listed in the Command (Action) column include READs or WRITEs with auto precharge enabled and
READs or WRITEs with auto precharge disabled.
11. Does not affect the state of the bank and acts as a NOP to that bank.
t
MRD is met, the SDRAM will be in the all banks idle state.
was HIGH and CKEn is HIGH (see Truth Table 2) and after tXSR has been met (if the
previous state was self refresh).
2. This table describes alternate bank operation, except where noted; i.e., the current state is for bank n and the
commands shown are those allowed to be issued to bank m (assuming that bank m is in such a state that the given
command is allowable). Exceptions are covered in the notes below.
3. Current state definitions:
Row Active: A row in the bank has been activated, and tRCD has been met. No data bursts/accesses and
Read w/Auto
Precharge Enabled: Starts with registration of a READ command with auto precharge enabled, and ends when
Write w/Auto
Precharge Enabled: Starts with registration of a WRITE command with auto precharge enabled, and ends when
n-1
Idle: The bank has been precharged, and tRP has been met.
no register accesses are in progress.
Re a d : A READ burst has been initiated, with auto precharge disabled, and has not yet terminated
or been terminated.
Write: A WR IT E b urst has been initiated, with auto precharge disabled, and has not yet
terminated or been terminated.
t
RP has been met. Once tRP is met, the bank will be in the idle state.
t
RP has been met. Once tRP is met, the bank will be in the idle state.
(Continued on next page)
30
Page 31
64Mb: x4, x8, x16
www.DataSheet4U.com
NOTE (continued):
4. AUTO REFRESH, SELF REFRESH and LOAD MODE REGISTER commands may only be issued when all banks are idle.
5. A BURST TERMINATE command cannot be issued to another bank; it applies to the bank represented by the current state
only.
6. All states and sequences not shown are illegal or reserved.
7. READs or WRITEs to bank m listed in the Command (Action) column include READs or WRITEs with auto precharge
enabled and READs or WRITEs with auto precharge disabled.
8. CONCURRENT AUTO PRECHARGE: Bank n will initiate the auto precharge command when its burst has been interrupted
by bank m’s burst.
9. Burst in bank n continues as initiated.
10. For a READ without auto precharge interrupted by a READ (with or without auto precharge), the READ to bank m will
interrupt the READ on bank n, CAS latency later (Figure 7).
11. For a READ without auto precharge interrupted by a WRITE (with or without auto precharge), the WRITE to bank m will
interrupt the READ on bank n when registered (Figures 9 and 10). DQM should be used one clock prior to the WRITE
command to prevent bus contention.
12. For a WRITE without auto precharge interrupted by a READ (with or without auto precharge), the READ to bank m will
interrupt the WRITE on bank n when registered (Figure 17), with the data-out appearing CAS latency later. The last
valid WRITE to bank n will be data-in registered one clock prior to the READ to bank m.
13. For a WRITE without auto precharge interrupted by a WRITE (with or without auto precharge), the WRITE to bank m
will interrupt the WRITE on bank n when registered (Figure 15). The last valid WRITE to bank n will be data-in
registered one clock prior to the READ to bank m.
14. For a READ with auto precharge interrupted by a READ (with or without auto precharge), the READ to bank m will
interrupt the READ on bank n, CAS latency later. The PRECHARGE to bank n will begin when the READ to bank m is
registered (Figure 24).
15. For a READ with auto precharge interrupted by a WRITE (with or without auto precharge), the WRITE to bank m will
interrupt the READ on bank n when registered. DQM should be used two clocks prior to the WRITE command to prevent
bus contention. The PRECHARGE to bank n will begin when the WRITE to bank m is registered (Figure 25).
16. For a WRITE with auto precharge interrupted by a READ (with or without auto precharge), the READ to bank m will
interrupt the WRITE on bank n when registered, with the data-out appearing CAS latency later. The PRECHARGE to bankn will begin after
will be data-in registered one clock prior to the READ to bank m (Figure 26).
17. For a WRITE with auto precharge interrupted by a WRITE (with or without auto precharge), the WRITE to bank m will
interrupt the WRITE on bank n when registered. The PRECHARGE to bank n will begin after tWR is met, where tWR
begins when the WRITE to bank m is registered. The last valid WRITE to bank n will be data registered one clock prior
to the WRITE to bank m (Figure 27).
t
WR is met, where tWR begins when the READ to bank m is registered. The last valid WRITE to bank n
Relative to VSS ............................................ -1V to +4.6V
Voltage on Inputs, NC or I/O Pins
Relative to V
Operating Temperature,
T
(commercial) ......................................0°C to +70°C
A
Operating Temperature,
SS ............................................ -1V to +4.6V
*Stresses greater than those listed under “Absolute
Maximum Ratings” may cause permanent damage to
the device. This is a stress rating only, and functional
operation of the device at these or any other conditions
above those indicated in the operational sections of
this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may
affect reliability.
TA (extended; IT parts)...................... -40°C to +85°C
Storage Temperature (plastic) ............ -55°C to +150°C
Power Dissipation ........................................................ 1W
DC ELECTRICAL CHARACTERISTICS AND OPERATING CONDITIONS
AC CHARACTERISTICS-6-7E-75-8E
PARAMETERSYMBOL MINMAXMINMA XMINMAXMINMA X UNITS NOTES
Access time from CLK (pos. edge)CL = 3tAC(3)5.55.45.46ns27
CL = 2tAC(2)–5.466ns
Address hold time
Address setup time
CLK high-level width
CLK low-level width
Clock cycle timeCL = 3tCK(3)677.58ns23
CL = 2tCK(2)–7.51010ns23
CKE hold time
CKE setup time
CS#, RAS#, CAS#, WE#, DQM hold time
CS#, RAS#, CAS#, WE#, DQM setup time
Data-in hold time
Data-in setup time
Data-out high-impedance timeCL = 3tHZ(3)5.55.45.46ns10
CL = 2tHZ(2)–5.466ns10
Data-out low-impedance time
Data-out hold time (load)
Data-out hold time (no load)
ACTIVE to PRECHARGE command
ACTIVE to ACTIVE command period
ACTIVE to READ or WRITE delay
Refresh period (4,096 rows)
AUTO REFRESH period
PRECHARGE command period
ACTIVE bank a to ACTIVE bank b command
Transition time
WRITE recovery time
READ/WRITE command to READ/WRITE command
CKE to clock disable or power-down entry mode
CKE to clock enable or power-down exit setup mode
t
CCD1111
t
CKED1111
t
PED1111
DQM to input data delay tDQD0000
DQM to data mask during WRITEs tDQM0000
DQM to data high-impedance during READs tDQZ2222
WRITE command to input data delay
Data-in to ACTIVE command
Data-in to PRECHARGE command
Last data-in to burst STOP command
Last data-in to new READ/WRITE command
Last data-in to PRECHARGE command
LOAD MODE REGISTER command to ACTIVE or REFRESH command
t
DWD0000
t
DAL5454
t
DPL2222
t
BDL1111
t
CDL1111
t
RDL2222
t
MRD2222
Data-out to high-impedance from PRECHARGE commandCL = 3tROH(3)3333
2. This parameter is sampled. VDD, VDDQ = +3.3V;
f = 1 MHz, TA = 25°C; pin under test biased at 1.4V.
DD is dependent on output loading and cycle rates.
3. I
Specified values are obtained with minimum cycle
time and the outputs open.
4. Enables on-chip refresh and address counters.
5. The minimum specifications are used only to
indicate cycle time at which proper operation over
the full temperature range (0°C £ TA £ +70°C and
-40°C £ T
6. An initial pause of 100µs is required after powerup, followed by two AUTO REFRESH commands,
before proper device operation is ensured. (VDD
and VDDQ must be powered up simultaneously. VSS
and VSSQ must be at same potential.) The two
AUTO REFRESH command wake-ups should be
repeated any time the tREF refresh requirement is
exceeded.
7. AC characteristics assume tT = 1ns.
8. In addition to meeting the transition rate specification, the clock and CKE must transit between VIH
and VIL (or between VIL and VIH) in a monotonic
manner.
9. Outputs measured at 1.5V with equivalent load:
10.tHZ defines the time at which the output achieves
the open circuit condition; it is not a reference to
VOH or VOL. The last valid data element will meet
t
OH before going High-Z.
11. AC timing and IDD tests have VIL = 0V and VIH = 3V,
with timing referenced to 1.5V crossover point. If
the input transition time is longer than 1 ns, then
the timing is referenced at VIL (MAX) and VIH (MIN)
and no longer at the 1.5V crossover point. CLK
should always be 1.5V referenced to crossover. Refer to Micron Technical Note TN-48-09
12. Other input signals are allowed to transition no
more than once every two clocks and are otherwise
at valid VIH or VIL levels.
£ +85°C for IT parts) is ensured.
A
Q
50pF
64Mb: x4, x8, x16
SDRAM
13. IDD specifications are tested after the device is properly initialized.
14. Timing actually specified by tCKS; clock(s) specified as a reference only at minimum cycle rate.
15. Timing actually specified by tWR plus tRP; clock(s)
specified as a reference only at minimum cycle rate.
16. Timing actually specified by tWR.
17. Required clocks are specified by JEDEC functionality and are not dependent on any timing parameter.
18. The IDD current will increase or decrease proportionally according to the amount of frequency alteration for the test condition.
19. Address transitions average one transition every
two clocks.
20. CLK must be toggled a minimum of two times during this period.
21. Based on tCK = 10ns for -8E , tCK=7.5ns for -75
and -7E, tCK = 6ns for -6.
22. VIH overshoot: VIH (MAX) = VDDQ + 2V for a pulse
width £ 3ns, and the pulse width cannot be greater
than one third of the cycle rate. VIL undershoot: VIL
(MIN) = -2V for a pulse width £ 3ns.
23. The clock frequency must remain constant (stable
clock is defined as a signal cycling within timing
constraints specified for the clock pin) during access or precharge states (READ, WRITE, including
t
WR, and PRECHARGE commands). CKE may be
used to reduce the data rate.
24. Auto precharge mode only. The precharge timing
budget (tRP) begins 6ns/7ns/7.5ns/7ns after the
first clock delay, after the last WRITE is executed.
25. Precharge mode only.
26. JEDEC and PC100 specify three clocks.
27.tAC for -75/-7E at CL = 3 with no load is 4.6ns and is
guaranteed by design.
28. Parameter guaranteed by design.
29. PC100 specifies a maximum of 4pF.
30. PC100 specifies a maximum of 5pF.
31. PC100 specifies a maximum of 6.5pF.
32. For -8E, CL = 2 and tCK = 10ns; for -75, CL = 3 and
t
CK = 7.5ns; for -7E, CL = 2 and tCK = 7.5ns; for -6,
CL = 3 and tCK = 6ns.
33. CKE is HIGH during refresh command period
t
RFC (MIN) else CKE is LOW. The IDD6 limit is actually a nominal value and does not result in a fail
value.