M48T129V 查看數據表（PDF） - STMicroelectronics
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M48T129V Datasheet PDF : 22 Pages
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Table 3. Operating Modes (1)
Mod e
VCC
E
G
Deselect
Write
Read
Read
4.5V to 5.5V
or
3.0V to 3.6V
VIH
X
VIL
X
VIL
VIL
VIL
VIH
Deselect
VSO to VPFD (min) (2)
X
X
Deselect
≤ VSO (2)
X
X
Note: 1. X = VIH or VIL; VSO = Battery Back-up Switchover Voltage.
2. See Table 7 for details.
M48T129Y, M48T129V
W
DQ0-DQ7
X
High Z
VIL
DIN
VIH
DOUT
VIH
High Z
X
High Z
Power
Standby
Active
Active
Active
CMOS Standby
X
High Z Battery Back-up Mode
DATA RETENTION MODE
With valid VCC applied, the M48T129Y/V operates
as a conventional BYTEWIDE™ static RAM.
Should the supply voltage decay, the RAM will au-
tomatically deselect, write protecting itself when
VCC falls between VPFD (max), VPFD (min) win-
dow. All outputs become high impedance and all
inputs are treated as ”don’t care”.
Note: A power failure during a write cycle may cor-
rupt data at the current addressed location, but
does not jeopardize the rest of the RAM’s content.
At voltages below VPFD (min), the memory will be
in a write protected state, provided the VCC fall
time is not less than tF. The M48T129Y/V may re-
spond to transient noise spikes on VCC that cross
into the deselect window during the time the de-
vice is sampling VCC. Therefore, decoupling of the
power supply lines is recommended.
When VCC drops below VSO, the control circuit
switches power to the internal battery, preserving
data and powering the clock. The internal energy
source will maintain data in the M48T129Y/V for
an accumulated period of at least 10 years at room
temperature. As system power rises above VSO,
the battery is disconnected, and the power supply
is switched to external VCC. Deselect continues for
tREC after VCC reaches VPFD (max). For a further
more detailed review of lifetime calculations,
please see Application Note AN1012.
TIMEKEEPER REGISTERS
The M48T129Y/V offers 16 internal registers
which contain TIMEKEEPER, Alarm, Watchdog,
Interrupt, Flag, and Control data. These registers
are memory locations which contain external (user
accessible) and internal copies of the data (usually
referred to as BiPORT TIMEKEEPER cells). The
Table 4. AC Measurement Conditions
Input Rise and Fall Times
≤ 5ns
Input Pulse Voltages
0 to 3V
Input and Output Timing Ref. Voltages
1.5V
Note that Output Hi-Z is defined as the point where data is no longer
driven.
Figure 5. AC Testing Load Circuit
DEVICE
UNDER
TEST
650Ω
CL = 100pF
1.75V
CL includes JIG capacitance
AI01803C
Note: Excluding open drain output pins
external copies are independent of internal func-
tions except that they are updated periodically by
the simultaneous transfer of the incremented inter-
nal copy. TIMEKEEPER and Alarm Registers
store data in BCD.
5/22
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