M48Z58Y ST Microelectronics, M48Z58Y Datasheet - Page 9

• Manufacturer Part Number: M48Z58Y
• Description: 64 Kbit 8Kb x 8 ZEROPOWER SRAM
• Manufacturer: ST Microelectronics

DATA RETENTION MODE
With valid V
as a conventional BYTEWIDE
Should the supply voltage decay, the RAM will
automatically power-fail deselect, write protecting
itself when V
V
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
content. At voltages below V
be assured the memory will be in a write protected
state, provided the V
The M48Z58/58Y 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 M48Z58/58Y for an accumulated period
of at least 10 years when V
As system power returns and V
the battery is disconnected, and the power supply
is switched to external V
tinues until V
Normal RAM operation can resume t
exceeds V
For more information on Battery Storage Life refer
to the Application Note AN1012.
PFD
(min) window. All outputs become high imped-
CC
PFD
CC
CC
drops below V
CC
(max).
that reach into the deselect window
applied, the M48Z58/58Y operates
CC
reaches V
f alls within the V
CC
fall time is not less than t
CC
PFD
CC
. Write protection con-
SO
PFD
(min) plus t
, the control circuit
is less than V
CC
(min), the user can
rises above V
static RAM.
REC
CC
PFD
REC
after V
. There-
(max),
SO
(min).
.
SO
CC
F
.
,
POWER SUPPLY DECOUPLING and UNDER-
SHOOT PROTECTION
I
switching, can produce voltage fluctuations, result-
ing in spikes on the V
be reduced if capacitors are used to store energy,
which stabilizes the V
the bypass capacitors will be released as low going
spikes are generated or energy will be absorbed
when overshoots occur. A ceramic bypass capaci-
tor value of 0.1 F (as shown in Figure 9) is recom-
mended in order to provide the needed filtering.
In addition to transients that are caused by normal
SRAM operation, power cycling can generate
negative voltage spikes on V
values below V
negative spikes can cause data corruption in the
SRAM while in battery backup mode. To protect
from these voltage spikes, it is recommeded to
connect a schottky diode from V
connected to V
1N5817 is recommended for through hole and
MBRS120T3 is recommended for surface mount.
Figure 9. Supply Voltage Protection
CC
transients, including those produced by output
V CC
0.1 F
SS
CC
, anode to V
by as much as one Volt. These
CC
CC
bus. These transients can
bus. The energy stored in
M48Z58, M48Z58Y
SS
CC
V CC
V SS
CC
). Schottky diode
to V
that drive it to
DEVICE
SS
AI02169
(cathode
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