CY14B256LA-ZS25XIT Cypress Semiconductor Corp, CY14B256LA-ZS25XIT Datasheet - Page 3

• Manufacturer Part Number: CY14B256LA-ZS25XIT
• Description: CY14B256LA-ZS25XIT
• Manufacturer: Cypress Semiconductor Corp

Specifications of CY14B256LA-ZS25XIT

• Format - Memory: RAM
• Memory Type: NVSRAM (Non-Volatile SRAM)
• Memory Size: 256K (32K x 8)
• Speed: 25ns
• Interface: Parallel
• Voltage - Supply: 2.7 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TSOP (0.400", 10.16mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Critical Considerations
The impact of the differences in CY14B256LA with respect
to the STK14C88-3 in existing applications are discussed
as follows. Board designers are recommended to review the
detailed datasheets when converting to the new part.
DC Parameters
The power supply design in most applications with
STK14C88-3 would require no changes when replacing the
nvSRAM with the CY14B256LA in spite of the higher values
in the operating / higher standby current. The critical
parameters to consider are the V
V
While most of the differences do not impact the application,
the difference in V
converting from the older rev parts. V
which provides the required charge for AutoStore to
complete NV store of the SRAM data during power down.
The required capacitor range is different in the two parts.
Table 6. V
Therefore, any existing application using a capacitor value
outside the overlapping range for the capacitor values needs
to consider the impact of capacitor dimensions while
changing to the new capacitor. Note: The capacitor range is
the absolute value of the capacitor, net of tolerence.
V
The STK14C88-3 operates from 3V while the CY14B256LA
operates from 2.7V. Hence the V
Table 7. V
The difference in levels do not affect most applications
except where the controller has operating range from 3.0V
and above. In such applications, if CY14B256LA is used to
replace STK14C88-3, at voltage levels below 3V, the
controller could be tristated and hence CY14B256LA could
write invalid data into the SRAM. This is because the
CY14B256LA would be active up to 2.7V. In such
application, it is necessary that the controller issues a reset
when the V
as the controller is inactive. This would initiate a Hardware
STORE in the CY14B256LA and the nvSRAM outputs would
be in tristate as long as the HSB is held LOW by the
controller.
AC Switching Parameters
There are a few minor differences in switching parameters
between the CY14B256LA and the STK14C88-3, as listed in
October 5, 2009
CAP
SWITCH
Description
Description
V
V
SWITCH
V
CAP
CC
CAP
CC
CC
, V
Comparison
crosses below 3V and remains LOW as long
SWITCH
54 uF to 264 uF
CAP
Comparison
2.7V to 2.95V
STK14C88-3
STK14C88-3
3.0V to 3.6V
is a critical consideration while
CAP
SWITCH
and the V
levels are different.
CAP
61 uF to 180 uF
CY14B256LA
CY14B256LA
is the capacitor
2.7V to 3.6V
SWITCH
<2.65V
Document No. 001-55662 Rev. **
the
applications. For replacing 35ns speed parts, choose the
25ns speed parts as replacement (since 35ns speed grade
is not available in the CY14B256LA).
AutoStore/Power Up RECALL Parameters
t
The
CY14B256LA compared to the STK14C88-3 because of
architecture differences.
Table 8. t
This difference is not likely to affect applications since the
initialization of the controller on the board happens at the
same time. However, this should be taken into consideration
when replacing the STK14C88-3 with CY14B256LA.
Software Controlled STORE/RECALL Cycle
Parameters
The Software cycle parameter t
CY14B256LA as described in the following section.
t
Software RECALL time (t
Table 9. t
This difference could require firmware change in the
application to increase the wait state when software
RECALL is initiated.
Software Sequence
The CY14B256LA is designed to be compatible with
STK14C88-3 in the software sequence modes. Hence, the
same Software STORE and RECALL address sequences in
STK14C88-3 works in CY14B256LA, requiring no firmware
change.
Hardware STORE Cycle Parameters
The Hardware STORE parameters are much improved in
the CY14B256LA. The improvements are listed under the
following section on
are required in applications.
HRECALL
RECALL
Description
Description
Table
t
t
HRECALL
RECALL
power
HRECALL
RECALL
5. However, these differences do not impact most
up
Comparison
Comparison
RECALL is much
Details of
STK14C88-3
STK14C88-3
550 us
RECALL
20 us
) is higher in CY14B256LA.
Improvement. No changes
RECALL
different in
CY14B256LA
CY14B256LA
is different in
200 us
20 ms
AN55662
the
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