differentiates the offerings in one place—
MT4LC16M4A7. The fifth field distinguishes
various options: A7 designates an 8K refresh and
T8 designates a 4K refresh for FPM DRAMs.
The 16 Meg x 4 DRAMs are high-speed CMOS,
dynamic random-access memory devices contain-ing
67,108,864 bits organized in a x4 configuration. The
MT4LC16M4A7 and MT4LC16M4T8 are functionally
organized as 16,777,216 locations containing four bits
each. The 16,777,216 memory locations are arranged in
8,192 rows by 2,048 columns for the MT4LC16M4A7 or
4,096 rows by 4,096 columns for the MT4LC16M4T8.
During READ or WRITE cycles, each location is uniquely
addressed via the address bits. First, the row address is
latched by the RAS# signal, then the column address by
CAS#. Both devices provide FAST-PAGE-MODE operation, allowing for fast successive data operations (READ,
WRITE, or READ-MODIFY-WRITE) within a given row.
The MT4LC16M4A7 and MT4LC16M4T8 must be
refreshed periodically in order to retain stored data.
FAST PAGE MODE ACCESS
Each location in the DRAM is uniquely addressable
as mentioned in the General Description. The data for
each location is accessed via the four I/O pins (DQ0DQ3). The WE# signal must be activated to execute a
WRITE operation; otherwise, a READ operation will be
performed. The OE# signal must be activated to enable
the DQ output drivers for a read access and can be
deactivated to disable output data if necessary.
FAST-PAGE-MODE operations are always initiated
with a row address strobed in by the RAS# signal,
followed by a column address strobed in by CAS#, just
like for single location accesses. However, subsequent
column locations within the row may then be accessed
at the page mode cycle time. This is accomplished by
cycling CAS# while holding RAS# LOW and entering
new column addresses with each CAS# cycle. Returning
RAS# HIGH terminates the FAST-PAGE-MODE operation.
DRAM REFRESH
The supply voltage must be maintained at the specified levels, and the refresh requirements must be met in
order to retain stored data in the DRAM. The refresh
requirements are met by refreshing all 8,192 rows (A7)
or all 4,096 rows (T8) in the DRAM array at least once
every 64ms. The recommended procedure is to execute
4,096 CBR REFRESH cycles, either uniformly spaced or
grouped in bursts, every 64ms. The MT4LC16M4A7
internally refreshes two rows for every CBR cycle,
16 MEG x 4
FPM DRAM
whereas the MT4LC16M4T8 refreshes one row for every
CBR cycle. So with either device, executing 4,096 CBR
cycles covers all rows. The CBR refresh will invoke the
internal refresh counter for automatic RAS# addressing. Alternatively, RAS#-ONLY REFRESH capability is
inherently provided. However, with this method only
one row is refreshed at a time; so for the MT4LC16M4A7,
8,192 RAS#-ONLY REFRESH cycles must be executed
every 64ms to cover all rows. Some compatibility issues
may become apparent. JEDEC strongly recommends
the use of CBR REFRESH for this device.
An optional self refresh mode is also available on the
“S” version. The self refresh feature is initiated by
performing a CBR REFRESH cycle and holding RAS#
LOW for the specified tRASS. The “S” option allows for
an extended refresh period of 128ms, or 31.25µs per
row for a 4K refresh and 15.625µs per row for an 8K
refresh, when using a distributed CBR REFRESH. This
refresh rate can be applied during normal operation, as
well as during a standby or battery backup mode.
The self refresh mode is terminated by driving RAS#
HIGH for a minimum time of tRPS. This delay allows for
the completion of any internal refresh cycles that may
be in process at the time of the RAS# LOW-to-HIGH
transition. If the DRAM controller uses a distributed
CBR refresh sequence, a burst refresh is not required
upon exiting self refresh. However, if the DRAM controller utilizes RAS#-ONLY or burst CBR refresh sequence, all rows must be refreshed within the average
internal refresh rate prior to the resumption of normal
operation.
STANDBY
Returning RAS# and CAS# HIGH terminates a
memory cycle and decreases chip current to a reduced
standby level. The chip is preconditioned for the next
cycle during the RAS# HIGH time.
Voltage on VCC Relative to VSS ................ -1V to +4.6V
Voltage on NC, Inputs or I/O Pins
Relative to VSS ..................................... -1V to +4.6V
Operating Temperature, TA (ambient) ... 0°C to +70°C
Storage Temperature (plastic) ............ -55°C to +150°C
Power Dissipation ................................................... 1W
*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.
DC ELECTRICAL CHARACTERISTICS AND OPERATING CONDITIONS
(Notes: 1, 5, 6) (VCC = +3.3V ±0.3V)
PARAMETER/CONDITIONSYMBOLMINMAXUNITS NOTES
SUPPLY VOLTAGEVCC33.6V
INPUT HIGH VOLTAGE:
Valid Logic 1; All inputs, I/Os and any NCVIH2VCC + 0.3V26
INPUT LOW VOLTAGE:
Valid Logic 0; All inputs, I/Os and any NCVIL-0.30.8V 26
INPUT LEAKAGE CURRENT:
Any input at VIN (0V ≤ VIN≤ VCC + 0.3V);II-22µA
All other pins not under test = 0V
OUTPUT HIGH VOLTAGE:
IOUT = -2mAVOH2.4–V
OUTPUT LOW VOLTAGE:
IOUT = 2mAVOL–0.4V
OUTPUT LEAKAGE CURRENT:
Any output at VOUT (0V ≤ VOUT ≤ VCC + 0.3V);IOZ-55µ A
DQ is disabled and in High-Z state
STANDBY CURRENT: CMOS
(RAS# = CAS# VCC - 0.2V, DQs may be left open,ICC2ALL500500µA
other inputs: VIN VCC - 0.2V or VIN≤ 0.2V)
OPERATING CURRENT: Random READ/WRITEICC3-5170130mA25
Average power supply current-6160120
(RAS#, CAS#, address cycling: tRC = tRC [MIN])
OPERATING CURRENT: FAST PAGE MODEICC4-5100100mA25
Average power supply current (RAS# = VIL,-69090
CAS#, address cycling: tPC = tPC [MIN])
REFRESH CURRENT: RAS#-ONLYICC5-5170130mA22
Average power supply current-6160120
(RAS# cycling, CAS# = VIH: tRC = tRC [MIN])
REFRESH CURRENT: CBRICC6-5170130mA4, 7
Average power supply current-6160120
(RAS#, CAS#, address cycling: tRC = tRC [MIN])
REFRESH CURRENT: Extended (“S” version only)
Average power supply current: CAS# = 0.2V or
CBR cycling; RAS# = tRAS (MIN); WE# = VCC - 0.2V;ICC7ALL400400µA4, 7
A0-A11, OE# and DIN = VCC - 0.2V or 0.2V
(DIN may be left open)
REFRESH CURRENT: Self (“S” version only)
Average power supply current: CBR withICC8ALL400400µA4, 7
RAS# tRASS (MIN) and CAS# held LOW;
WE# = VCC - 0.2V; A0-A11, OE# and DIN =
VCC - 0.2V or 0.2V (DIN may be left open)
AC CHARACTERISTICS-5-6
PARAMETERSYMBOLMINMAXMINMAXUNITSNOTES
Access time from column address
Column-address hold time (referenced to RAS#)
Column-address setup time
Row-address setup time
Column address to WE# delay time
Access time from CAS#
Column-address hold time
CAS# pulse width
CAS# LOW to “Don’t Care” during Self Refresh
CAS# hold time (CBR Refresh)
CAS# to output in Low-Z
CAS# precharge time (FAST PAGE MODE)
Access time from CAS# precharge
CAS# to RAS# precharge time
CAS# hold time
CAS# setup time (CBR Refresh)
CAS# to WE# delay time
WRITE command to CAS# lead time
Data-in hold time
Data-in setup time
Output disable
Output enable time
OE# hold time from WE# during
AC CHARACTERISTICS-5-6
PARAMETERSYMBOLMINMAXMINMAXUNITSNOTES
Row-address hold time
RAS# pulse width
RAS# pulse width (FAST PAGE MODE)
RAS# pulse width during Self Refresh
Random READ or WRITE cycle time
RAS# to CAS# delay time
READ command hold time (referenced to CAS#)
READ command setup time
Refresh period
Refresh period (4,096 cycles) “S” version
RAS# precharge time
RAS# to CAS# precharge time
RAS# precharge time exiting Self Refresh
READ command hold time (referenced to RAS#)
RAS# hold time
READ-WRITE cycle time
RAS# to WE# delay time
WRITE command to RAS# lead time
Transition time (rise or fall)
WRITE command hold time
WRITE command hold time (referenced to RAS#)
WE# command setup time
WRITE command pulse width
WE# hold time (CBR Refresh)
WE# setup time (CBR Refresh)
rates. 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 is ensured.
6. An initial pause of 100µs is required after power-
up, followed by eight RAS# refresh cycles (RAS#ONLY or CBR with WE# HIGH), before proper
device operation is ensured. The eight RAS# cycle
wake-ups should be repeated any time the tREF
refresh requirement is exceeded.
7. AC characteristics assume tT = 5ns.
8. VIH (MIN) and VIL (MAX) are reference levels for
measuring timing of input signals. Transition
times are measured between VIH and VIL (or
between VIL and VIH).
9. In addition to meeting the transition rate
specification, all input signals must transit
between VIH and VIL (or between VIL and VIH) in a
monotonic manner.
10. If CAS# = VIH, data output is High-Z.
11. If CAS# = VIL, data output may contain data from
the last valid READ cycle.
12. Measured with a load equivalent to two TTL
gates, 100pF and VOL = 0.8V and VOH = 2V.
13. If CAS# is LOW at the falling edge of RAS#,
output data will be maintained from the previous
cycle. To initiate a new cycle and clear the dataout buffer, CAS# must be pulsed HIGH for tCP.
14. The tRCD (MAX) limit is no longer specified.
t
RCD (MAX) was specified as a reference point
only. If tRCD was greater than the specified tRCD
(MAX) limit, then access time was controlled
exclusively by tCAC (tRAC [MIN] no longer
applied). With or without the tRCD limit, tAA
and tCAC must always be met.
15. The tRAD (MAX) limit is no longer specified.
t
RAD (MAX) was specified as a reference point
only. If tRAD was greater than the specified tRAD
(MAX) limit, then access time was controlled
exclusively by tAA (tRAC and tCAC no longer
applied). With or without the tRAD (MAX) limit,
t
AA, tRAC, and tCAC must always be met.
16. Either tRCH or tRRH must be satisfied for a READ
cycle.
17.tOFF (MAX) defines the time at which the output
achieves the open circuit condition and is not
referenced to VOH or VOL.
16 MEG x 4
FPM DRAM
18.tWCS, tRWD, tAWD, and tCWD are not
restrictive operating parameters. tWCS applies to
EARLY WRITE cycles. If tWCS > tWCS (MIN), the
cycle is an EARLY WRITE cycle and the data
output will remain an open circuit throughout
the entire cycle. tRWD, tAWD, and tCWD define
READ-MODIFY-WRITE cycles. Meeting these
limits allows for reading and disabling output
data and then applying input data. The values
shown were calculated for reference allowing
10ns for the external latching of read data and
application of write data. OE# held HIGH and
WE# taken LOW after CAS# goes LOW result in a
LATE WRITE (OE#-controlled) cycle. tWCS,
t
RWD, tCWD and tAWD are not applicable in a
LATE WRITE cycle.
19. These parameters are referenced to CAS# leading
edge in EARLY WRITE cycles and WE# leading
edge in LATE WRITE or READ-MODIFY-WRITE
cycles.
20. If OE# is tied permanently LOW, LATE WRITE or
READ-MODIFY-WRITE operations are not
possible.
21. A HIDDEN REFRESH may also be performed after
a WRITE cycle. In this case, WE# = LOW and OE#
= HIGH.
22. RAS#-ONLY REFRESH requires that all 8,192 rows
of the MT4LC16M4A7 or all 4,096 rows of the
MT4LC16M4T8 be refreshed at least once every
64ms. CBR REFRESH for either device requires
that at least 4,096 cycles be completed every
64ms.
23. The DQs open during READ cycles once tOD or
t
OFF occur. If CAS# goes HIGH before OE#, the
DQs will open regardless of the state of OE#. If
CAS# stays LOW while OE# is brought HIGH, the
DQs will open. If OE# is brought back LOW
(CAS# still LOW), the DQs will provide the
previously read data.
24. LATE WRITE and READ-MODIFY-WRITE cycles
must have both tOD and tOEH met (OE# HIGH
during WRITE cycle) in order to ensure that the
output buffers will be open during the WRITE
cycle. If OE# is taken back LOW while CAS#
remains LOW, the DQs will remain open.
25. Column address changed once each cycle.
26. VIH overshoot: VIH (MAX) = VCC + 2V for a pulse
width ≤ 10ns, and the pulse width cannot be
greater than one third of the cycle rate. VIL
undershoot: VIL (MIN) = -2V for a pulse width ≤
10ns, and the pulse width cannot be greater than
one third of the cycle rate.