m48z18 STMicroelectronics, m48z18 Datasheet - Page 8

• Manufacturer Part Number: m48z18
• Description: 5v, 64 Kbit 8kb X 8 Zeropower Sram
• Manufacturer: STMicroelectronics

M48Z08, M48Z18
Data Retention Mode
With valid V
as a conventional BYTEWIDE™ static RAM.
Should the supply voltage decay, the RAM will au-
tomatically power-fail deselect, write protecting it-
self when V
(min) window. All outputs become high imped-
ance, and all inputs are treated as “Don't care.”
Note: A power failure during a WRITE cycle may
corrupt data at the currently addressed location,
but does not jeopardize the rest of the RAM's con-
tent. At voltages below V
assured the memory will be in a write protected
state, provided the V
The M48Z08/18 may respond to transient noise
spikes on V
during the time the device is sampling V
fore, decoupling of the power supply lines is rec-
ommended.
When V
switches power to the internal battery which pre-
serves data. The internal button cell will maintain
data in the M48Z08/18 for an accumulated period
of at least 11 years when V
As system power returns and V
V
supply is switched to external V
tion continues until V
t
V
to system stabilization. Normal RAM operation can
resume t
For more information on Battery Storage Life refer
to the Application Note AN1012.
8/16
rec
SO
PFD
(min). E should be kept high as V
, the battery is disconnected, and the power
(min) to prevent inadvertent write cycles prior
CC
rec
CC
after V
drops below V
CC
CC
that reach into the deselect window
falls within the V
applied, the M48Z08/18 operates
CC
CC
CC
exceeds V
fall time is not less than t
PFD
reaches V
CC
SO
(min), the user can be
, the control circuit
is less than V
PFD
CC
PFD
CC
. Write protec-
PFD
(max).
CC
(max), V
rises above
CC
(min) plus
rises past
. There-
SO
PFD
.
F
.
V
I
switching, can produce voltage fluctuations, re-
sulting in spikes on the V
can be reduced if capacitors are used to store en-
ergy which stabilizes the V
stored in the bypass capacitors will be released as
low going spikes are generated or energy will be
absorbed when overshoots occur. A ceramic by-
pass capacitor value of 0.1µF (as shown in
8.) is recommended in order to provide the needed
filtering.
In addition to transients that are caused by normal
SRAM operation, power cycling can generate neg-
ative voltage spikes on V
below V
spikes can cause data corruption in the SRAM
while in battery backup mode. To protect from
these voltage spikes, STMicroelectronics recom-
mends connecting a schottky diode from V
V
Schottky diode 1N5817 is recommended for
through hole and MBRS120T3 is recommended
for surface mount.
Figure 8. Supply Voltage Protection
CC
CC
SS
transients, including those produced by output
Noise And Negative Going Transients
(cathode connected to V
SS
V CC
by as much as one volt. These negative
0.1 F
CC
CC
bus. These transients
CC
that drive it to values
CC
V CC
V SS
bus. The energy
, anode to V
DEVICE
AI02169
Figure
CC
SS
to
).