BQ4014_08 Datasheet, PDF (1/13 Pages) Texas Instruments – 256Kx8 Nonvolatile SRAM

bq4014/bq4014Y
256Kx8 Nonvolatile SRAM
Features
® Data retention in the absence of
power
® Automatic write-protection
during power-up/power-down
cycles
® Industry-standard 32-pin 256K x
8 pinout
® Conventional SRAM operation;
unlimited write cycles
® 10-year minimum data retention
in absence of power
® Battery internally isolated until
power is applied
General Description
The CMOS bq4014 is a nonvolatile
2,097,152-bit static RAM organized as
262,144 words by 8 bits. The integral
control circuitry and lithium energy
source provide reliable nonvolatility
coupled with the unlimited write
cycles of standard SRAM.
The control circuitry constantly
monitors the single 5V supply for an
out-of-tolerance condition. When
VCC falls out of tolerance, the SRAM
is unconditionally write-protected to
prevent inadvertent write operation.
At this time the integral energy
source is switched on to sustain the
memory until after VCC returns
valid.
The bq4014 uses extremely low
standby current CMOS SRAMs,
coupled with small lithium coin
cells to provide nonvolatility without
long write-cycle times and the write-
cycle limitations associated with
EEPROM.
The bq4014 requires no external cir-
cuitry and is compatible with the
industry-standard 2Mb SRAM
pinout.
Pin Connections
Pin Names
A0–A17 Address inputs
DQ0–DQ7 Data input/output
CE
Chip enable input
OE
Output enable input
WE
Write enable input
NC
No connect
VCC
+5 volt supply input
VSS
Ground
Block Diagram
Selection Guide
Part
Number
Maximum
Access
Time (ns)
bq4014 -85
85
bq4014 -120
120
Sept. 1992
Negative
Supply
Tolerance
-5%
-5%
Part
Number
bq4014Y -85
bq4014Y -120
1
Maximum
Access
Time (ns)
85
120
Negative
Supply
Tolerance
-10%
-10%