m48z128 STMicroelectronics, m48z128 Datasheet - Page 11

• Manufacturer Part Number: m48z128
• Description: 5.0v Or 3.3v, 1 Mbit 128 Kbit X 8 Zeropower Sram
• Manufacturer: STMicroelectronics

Data Retention Mode
With valid V
ates as a conventional BYTEWIDE
Should the supply voltage decay, the RAM will au-
tomatically power-fail deselect, write protecting it-
self t
become high impedance, and all inputs are treated
as “Don't care.”
If power fail detection occurs during a valid ac-
cess, the memory cycle continues to completion. If
the memory cycle fails to terminate within the time
t
below V
the internal energy source which preserves data.
The internal coin cell will maintain data in the
M48Z128/Y/V after the initial application of V
an accumulated period of at least 10 years when
V
and V
nected, and the power supply is switched to exter-
nal V
V
tion. After t
For more information on Battery Storage Life refer
to the Application Note AN1012.
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 (see
recommended in order to provide the needed fil-
tering.
WP
CC
CC
CC
CC
, write protection takes place. When V
transients, including those produced by output
reaches V
Noise And Negative Going Transients
is less than V
WP
CC
CC
. Write protection continues for t
SO
after V
rises above V
ER
, the control circuit switches power to
CC
, normal RAM operation can resume.
PFD
CC
applied, the M48Z128/Y/V oper-
to allow for processor stabiliza-
SO
falls below V
. As system power returns
SO
CC
, the battery is discon-
bus. These transients
CC
bus. The energy
PFD
™
Figure
. All outputs
static RAM.
CC
ER
10.) is
CC
drops
after
for
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, ST recommends connecting
a schottky diode from V
nected to V
1N5817 is recommended for through hole and
MBRS120T3 is recommended for surface-mount).
Figure 10. Supply Voltage Protection
SS
V CC
M48Z128, M48Z128Y, M48Z128V*
by as much as one volt. These negative
0.1 F
CC
, anode to V
CC
CC
to V
that drive it to values
SS
). (Schottky diode
V CC
V SS
SS
DEVICE
(cathode con-
AI02169
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