DS1345Y Maxim, DS1345Y Datasheet - Page 2

• Manufacturer Part Number: DS1345Y
• Description: The DS1345 1024k Nonvolatile (NV) SRAMs are 1,048,576-bit, fully static, NV SRAMs organized as 131,072 words by 8 bits
• Manufacturer: Maxim

READ MODE
The DS1345 devices execute a read cycle whenever
Enable) and
(A
eight data output drivers within t
that
satisfied, then data access must be measured from the later-occurring signal (
parameter is either t
WRITE MODE
The DS1345 devices execute a write cycle whenever the
after address inputs are stable. The later-occurring falling edge of
the write cycle. The write cycle is terminated by the earlier rising edge of
must be kept valid throughout the write cycle.
time (t
during write cycles to avoid bus contention. However, if the output drivers are enabled (
active) then
DATA RETENTION MODE
The DS1345AB provides full functional capability for V
The DS1345Y provides full functional capability for V
Data is maintained in the absence of V
RAMs constantly monitor V
protect themselves, all inputs become “don’t care,” and all outputs become high impedance. As V
below approximately 2.7V, the power switching circuit connects the lithium energy source to RAM to
retain data. During power-up, when V
connects external V
can resume after V
SYSTEM POWER MONITORING
DS1345 devices have the ability to monitor the external V
power supply condition is detected, the NV SRAMs warn a processor-based system of impending power
failure by asserting
operation during power-on transients and to allow t
BATTERY MONITORING
The DS1345 devices automatically perform periodic battery voltage monitoring on a 24-hour time
interval. Such monitoring begins within t
failure occurs.
After each 24-hour period has elapsed, the battery is connected to an internal 1MΩ test resistor for one
second. During this one second, if battery voltage falls below the battery voltage trip point (2.6V), the
battery warning output
The battery is still retested after each V
is found to be higher than 2.6V during such testing,
resumes.
0
– A
CE
WR
16
and
) defines which of the 131,072 bytes of data is to be accessed. Valid data will be available to the
) before another cycle can be initiated. The
BW
WE
OE
OE
has an open drain output driver.
(Output Enable) are active (low). The unique address specified by the 17 address inputs
will disable the outputs in t
(Output Enable) access times are also satisfied. If
CC
CO
CC
exceeds 4.75V for the DS1345AB and 4.5V for the DS1345Y.
RST
for
to the RAM and disconnects the lithium energy source. Normal RAM operation
BW
. On power-up,
CE
is asserted. Once asserted,
CC
or t
. Should the supply voltage decay, the NV SRAMs automatically write
ACC
OE
for
(Access Time) after the last address input signal is stable, providing
CC
CC
CC
OE
power-up, however, even if
without any additional support circuitry. The nonvolatile static
REC
rises above approximately 2.7V, the power switching circuit
ODW
rather than address access.
RST
after V
WE
from its falling edge.
is held active for 200ms nominal to prevent system
REC
must return to the high state for a minimum recovery
WE
2 of 10
CC
to elapse.
CC
OE
CC
BW
(Write Enable) is inactive (high) and
BW
rises above V
WE
greater than 4.5V and write protects by 4.25V.
greater than 4.75V and write protects by 4.5V.
control signal should be kept inactive (high)
CC
remains active until the module is replaced.
is de-asserted and regular 24-hour testing
and
power supply. When an out-of-tolerance
RST
CE
CE
has an open drain output driver.
signals are in the active (low) state
BW
OE
or
TP
and is suspended when power
WE
is active. If the battery voltage
CE
and
CE
or
will determine the start of
CE
or
WE
access times are not
OE
. All address inputs
) and the limiting
CE
DS1345Y/AB
CE
and
(Chip
CC
falls
OE