Applying the STK11C/15C/16C88
The addition of a low forward voltage drop diode,
and a 100µF capacitor will supply the energy neces-
sary for the STORE operation to complete indepen-
dent of the Power Supply decay characteristics
(Figure 3). The optional resistor on W prevents acci-
dental writes to the SRAM in systems whose power
Applications
Simtek's family of nvSRAMs is the ideal comple-
ment to many of today's most advanced technolo-
gies. By increasing the level of integration, designs
can be achieved that are smaller (more compact),
lower in power, higher reliability, lower cost, and
much higher performance than possible just a few
years ago.
supply is unreliable on power-up above VSWITCH
.
Note that this alternate configuration effectively
raises the VSWITCH level by the diode drop Vf.
FPGA/PGA
Many manufacturers of programmable gate arrays
require high speed nonvolatile memory to load con-
figuration table data into their programmable arrays.
Combining the high speed and density of Gate Array
devices from Xylinx and Altera, with the advanced
capability of the Simtek 32K x 8 family of nonvolatile
memories, opens the door to many new embedded
applications. Adaptive security systems, video/tele-
com Digi-Cypher, and automotive theft protection
and recovery systems are just a few of the potential
applications for embedded PGA/ nvSRAM systems
(Figure 4).
28
27
1
+
Altera
EPF8150
0
Data Bus
14
DQ0-DQ7
(EPLD)
Simtek
STK11C88
nvSRAM
Figure 3
Address Bus
A0-A14
Alternate STK15C88 AutoStore™ Implementation
CONF_DONE
nCONFIG
G
W
E
STK16C88 Nonvolatile Operations
The STK16C88 is a close relation to the STK15C88.
Its software STORE and RECALL operations, and
its power-up RECALL capabilities are identical. The
AutoStorePlus™ feature of the STK16C88 provides
automatic STORE of SRAM data to EEPROM on
power-down that is independent of the power supply
decay rate. The AutoStorePlus™ is initiated 1µs
after the detection of power failure (the transition
through VSWITCH) and does not depend upon the
power supply to complete the STORE cycle. It is the
ideal standard pin-out solution in systems whose
power supply decays very quickly. To a design engi-
neer who cannot guarantee the 10ms required by
the STK15C88 to execute a STORE on power-
down, the STK16C88 is a simpler solution requiring
no additional components.
System Reset
R/W
System Reset must be long
enough for STK11C88 to
RECALL data (550us max)
Processor Reset must not be
released until EPLD has
completed load
Embedded
Processor
I/O
Processor Board
Figure 4
Altera EPF81500 EPLD in a parallel load
configuration with the SIMTEK STK11C88
256K “Fast” nvSRAM
By using a single STK11C88 nvSRAM to parallel
load configuration data to an Altera EPLD, and by
using the same memory as a fast SRAM for proces-
sor scratch pad RAM memory, the design engineer
can realize a significant reduction in parts count and
cost. At system power-up, the EPF81500 is held in a
8-23
SIMTEK [ SIMTEK CORPORATION ]
