M48T02-150PC1TR STMICROELECTRONICS [STMicroelectronics], M48T02-150PC1TR Datasheet - Page 10

• Manufacturer Part Number: M48T02-150PC1TR
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M48T02, M48T12
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 M48T02/12 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.
The power switching circuit connects external V
to the RAM and disconnects the battery when V
rises above V
is checked. If the voltage is too low, an internal
Battery Not OK (BOK) flag will be set. The BOK
flag can be checked after power up. If the BOK flag
is set, the first WRITE attempted will be blocked.
The flag is automatically cleared after the first
WRITE, and normal RAM operation resumes. Fig-
ure 9 illustrates how a BOK check routine could be
structured.
For more information on a Battery Storage Life re-
fer to the Application Note AN1012.
10/19
CC
CC
CC
SO
that reach into the deselect window
falls within the V
applied, the M48T02/12 operates
. As V
CC
CC
fall time is not less than t
PFD
rises, the battery voltage
(min), the user can be
PFD
(max), V
CC
. There-
PFD
CC
CC
F
.
Figure 9. Checking the BOK Flag Status
(BATTERY OK)
COMPLEMENT BACK
TO SAME ADDRESS
AT ANY ADDRESS
ADDRESS AGAIN
WRITE ORIGINAL
SAME ADDRESS
DATA BACK TO
COMPLEMENT
WRITE DATA
READ DATA
READ DATA
POWER-UP
CONTINUE
AT SAME
OF FIRST
IS DATA
READ?
YES
NO
OF LOW BATTERY
(BATTERY LOW)
NOTIFY SYSTEM
(DATA MAY BE
CORRUPTED)
AI00607