L7C185
DEVICES INCORPORATED
8K x 8 Static RAM (Low Power)
L7C185
DEVICES INCORPORATED
8K x 8 Static RAM (Low Power)
DESCRIPTION
The
L7C185
is a high-performance,
low-power CMOS static RAM. The
storage circuitry is organized as 8,192
words by 8 bits per word. The 8 Data
In and Data Out signals share I/O
pins. These devices are available in
four speeds with maximum access
times from 12 ns to 25 ns.
Inputs and outputs are TTL compat-
ible. Operation is from a single +5 V
power supply. Power consumption
for the L7C185 is 425 mW (typical) at
25 ns. Dissipation drops to 60 mW
(typical) for the L7C185 and 50 mW
(typical) for the L7C185-L when the
memory is deselected.
Two standby modes are available.
Proprietary Auto-Powerdown™
circuitry reduces power consumption
automatically during read or write
accesses which are longer than the
minimum access time, or when the
memory is deselected. In addition,
data may be retained in inactive
storage with a supply voltage as low
as 2 V. The L7C185 and L7CL185-L
consume only 30 µW and 15 µW
(typical) respectively at 3 V, allowing
effective battery backup operation.
The L7C185 provides asynchronous
(unclocked) operation with matching
access and cycle times. Two Chip
Enables (one active-low) and a three-
state I/O bus with a separate Output
Enable control simplify the connection
of several chips for increased storage
capacity.
Memory locations are specified on
address pins A
0
through A
12
. Read-
ing from a designated location is
accomplished by presenting an
address and driving CE
1
and OE
LOW, and CE
2
and WE HIGH. The
data in the addressed memory
location will then appear on the Data
Out pins within one access time. The
output pins stay in a high-impedance
state when CE
1
or OE is HIGH, or CE
2
or WE is LOW.
Writing to an addressed location is
accomplished when the active-low
CE
1
and WE inputs are both LOW,
and CE
2
is HIGH. Any of these
signals may be used to terminate the
write operation. Data In and Data Out
signals have the same polarity.
Latchup and static discharge pro-
tection are provided on-chip. The
L7C185 can withstand an injection
current of up to 200 mA on any pin
without damage.
FEATURES
q
8K x 8 Static RAM with Chip Select
Powerdown, Output Enable
q
Auto-Powerdown™ Design
q
Advanced CMOS Technology
q
High Speed — to 12 ns maximum
q
Low Power Operation
Active:
425 mW typical at 25 ns
Standby (typical):
400µW (L7C185)
200 µW (L7C185-L)
q
Data Retention at 2 V for Battery
Backup Operation
q
DESC SMD No. 5962-38294
q
Available 100% Screened to
MIL-STD-883, Class B
q
Plug Compatible with IDT7164,
Cypress CY7C185/186
q
Package Styles Available:
• 28-pin Plastic DIP
• 28-pin Ceramic DIP
• 28-pin Plastic SOJ
• 28-pin Ceramic Flatpack
• 28-pin Ceramic LCC
• 32-pin Ceramic LCC
L7C185 B
LOCK
D
IAGRAM
ROW SELECT
ROW
ADDRESS
8
256 x 32 x 8
MEMORY
ARRAY
CE
1
CE
2
WE
OE
CONTROL
COLUMN SELECT
& COLUMN SENSE
5
8
I/O
7-0
COLUMN ADDRESS
64K Static RAMs
1
03/06/95–LDS.185-D
L7C185
DEVICES INCORPORATED
8K x 8 Static RAM (Low Power)
NOTES
1. Maximum Ratings indicate stress specifi-
cations only. Functional operation of these
products at values beyond those indicated
in the Operating Conditions table is not
implied. Exposure to maximum rating con-
ditions for extended periods may affect re-
liability of the tested device.
2. The products described by this specifica-
tion include internal circuitry designed to
protect the chip from damaging substrate
injection currents and accumulations of
static charge. Nevertheless, conventional
precautions should be observed during
storage, handling, and use of these circuits
in order to avoid exposure to excessive elec-
trical stress values.
3. This product provides hard clamping of
transient undershoot. Input levels below
ground will be clamped beginning at –0.6 V.
A current in excess of 100 mA is required to
reach –2.0 V. The device can withstand in-
definite operation with inputs as low as –3 V
subject only to power dissipation and bond
wire fusing constraints.
4. Tested with GND
≤
V
OUT
≤
V
CC
. The de-
vice is disabled, i.e., CE
1
=
V
CC
, CE
2
= GND.
5. A series of normalized curves is available
to supply the designer with typical DC and
AC parametric information for Logic Devices
Static RAMs. These curves may be used to
determine device characteristics at various
temperatures and voltage levels.
6. Tested with all address and data inputs
changing at the maximum cycle rate. The
device is continuously enabled for writing,
i.e., CE
1
≤
V
IL
, CE
2
≥
V
IH
, WE
≤
V
IL
. Input
pulse levels are 0 to 3.0 V.
7. Tested with outputs open and all address
and data inputs changing at the maximum
read cycle rate. The device is continuously
disabled, i.e., CE
1
≥
V
IH
, CE
2
≤
V
IL
.
8. Tested with outputs open and all ad-
dress and data inputs stable. The device is
continuously disabled, i.e., CE
1
=
V
CC
,
CE
2
= GND. Input levels are within 0.2 V
of
V
CC
or GND.
9. Data retention operation requires that
V
CC
never drop below 2.0 V. CE
1
must be
≥
V
CC
– 0.2 V or CE
2
must be
≤
0.2 V. All
other inputs must meet
V
IN
≥
V
CC
– 0.2 V or
V
IN
≤
0.2 V to ensure full powerdown. For
low power version (if applicable), this re-
quirement applies only to CE
1
, CE
2
, and
WE; there are no restrictions on data and
address.
10. These parameters are guaranteed but
not 100% tested.
11. Test conditions assume input transition
times of less than 3 ns, reference levels of
1.5 V, output loading for specified
I
OL
and
I
OH
plus 30 pF (Fig. 1a), and input pulse
levels of 0 to 3.0 V (Fig. 2).
12. Each parameter is shown as a minimum
or maximum value. Input requirements are
specified from the point of view of the exter-
nal system driving the chip. For example,
t
AVEW
is specified as a minimum since the
external system must supply at least that
much time to meet the worst-case require-
ments of all parts. Responses from the inter-
nal circuitry are specified from the point of
view of the device. Access time, for ex-
ample, is specified as a maximum since
worst-case operation of any device always
provides data within that time.
13. WE is high for the read cycle.
14. The chip is continuously selected (CE
1
low, CE
2
high).
15. All address lines are valid prior-to or
coincident-with the CE
1
and CE
2
transition
to active.
16. The internal write cycle of the memory
is defined by the overlap of CE
1
and CE
2
active and WE low. All three signals must be
active to initiate a write. Any signal can
terminate a write by going inactive. The
address, data, and control input setup and
hold times should be referenced to the sig-
nal that becomes active last or becomes inac-
tive first.
17. If WE goes low before or concurrent
with the latter of CE
1
and CE
2
going active,
the output remains in a high impedance
state.
18. If CE
1
and CE
2
goes inactive before or
concurrent with WE going high, the output
remains in a high impedance state.
19. Powerup from
I
CC2
to
I
CC1
occurs as a
result of any of the following conditions:
a. Rising edge of CE
2
(CE
1
active) or the
falling edge of CE
1
(CE
2
active).
b. Falling edge of WE (CE
1
, CE
2
active).
c. Transition on any address line (CE
1
, CE
2
active).
d. Transition on any data line (CE
1
, CE
2
,
and WE active).
The device automatically powers down
from
I
CC1
to
I
CC2
after
t
PD
has elapsed from
any of the prior conditions. This means that
power dissipation is dependent on only
cycle rate, and is not on Chip Select pulse
width.
INCLUDING
JIG AND
SCOPE
20. At any given temperature and voltage
condition, output disable time is less than
output enable time for any given device.
21. Transition is measured ±200 mV from
steady state voltage with specified loading
in Fig. 1b. This parameter is sampled and
not 100% tested.
22. All address timings are referenced from
the last valid address line to the first transi-
tioning address line.
23. CE
1
, CE
2
, or WE must be inactive during
address transitions.
24. This product is a very high speed device
and care must be taken during testing in
order to realize valid test information. In-
adequate attention to setups and proce-
dures can cause a good part to be rejected as
faulty. Long high inductance leads that
cause supply bounce must be avoided by
bringing the
V
CC
and ground planes di-
rectly up to the contactor fingers. A 0.01 µF
high frequency capacitor is also required
between
V
CC
and ground. To avoid signal
reflections, proper terminations must be
used.
F
IGURE
1a.
R
1
480
Ω
+5 V
OUTPUT
INCLUDING
JIG AND
SCOPE
30 pF
R
2
255
Ω
F
IGURE
1b.
+5 V
OUTPUT
R
2
255
Ω
R
1
480
Ω
5 pF
F
IGURE
2.
+3.0 V
10%
90%
90%
10%
<3 ns
GND
<3 ns
64K Static RAMs
5
03/06/95–LDS.185-D
Microcontroller MCU
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