U635H256
Not Recommended For New Designs
Features
High-performance CMOS non
volatile static RAM 32768 x 8 bits
25 ns Access Time
10 ns Output Enable Access
Time
I
CC
= 15 mA typ. at 200 ns Cycle
Time
Automatic STORE to EEPROM
on Power Down using system
capacitance
Software initiated STORE
Automatic STORE Timing
10
6
STORE cycles to EEPROM
100 years data retention in
EEPROM
Automatic RECALL on Power Up
Software RECALL Initiation
Unlimited RECALL cycles from
EEPROM
Single 5 V
±
10 % Operation
Operating temperature range:
0 to 70
°C
-40 to 85°C
QS 9000 Quality Standard
ESD protection > 2000 V
(MIL STD 883C M3015.7-HBM)
RoHS compliance and Pb- free
Package: SOP28 (330 mil)
Description
The U635H256 has two separate
modes of operation: SRAM mode
and nonvolatile mode. In SRAM
mode, the memory operates as an
ordinary static RAM. In nonvolatile
operation, data is transferred in
parallel from SRAM to EEPROM or
from EEPROM to SRAM. In this
mode SRAM functions are disab-
led.
The U635H256 is a fast static RAM
(25 ns), with a nonvolatile electri-
cally erasable PROM (EEPROM)
element incorporated in each static
memory cell. The SRAM can be
read and written an unlimited num-
ber of times, while independent
nonvolatile
data
resides
in
EEPROM. Data transfers from the
SRAM to the EEPROM (the
STORE operation) take place auto-
matically upon power down using
charge stored in system capaci-
tance.
Transfers
from
the
EEPROM to the SRAM (the
RECALL operation) take place
automatically on power up. The
U635H256 combines the high per-
formance and ease of use of a fast
SRAM with nonvolatile data inte-
Pin Description
28
27
26
25
24
23
22
VCC
W
A13
A8
A9
A11
G
A10
E
DQ7
DQ6
DQ5
DQ4
DQ3
PowerStore
32K x 8 nvSRAM
grity.
STORE cycles also may be initia-
ted under user control via a soft-
ware sequence.
Once a STORE cycle is initiated,
further input or output are disabled
until the cycle is completed.
Because a sequence of addresses
is used for STORE initiation, it is
important that no other read or
write accesses intervene in the
sequence or the sequence will be
aborted.
RECALL cycles may also be initia-
ted by a software sequence.
Internally, RECALL is a two step
procedure. First, the SRAM data is
cleared and second, the nonvola-
tile information is transferred into
the SRAM cells.
The RECALL operation in no way
alters the data in the EEPROM
cells. The nonvolatile data can be
recalled an unlimited number of
times.
The U635H256 is pin compatible
with standard SRAMs.
Pin Configuration
A14
A12
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
VSS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Signal Name
A0 - A14
DQ0 - DQ7
E
G
W
VCC
VSS
Signal Description
Address Inputs
Data In/Out
Chip Enable
Output Enable
Write Enable
Power Supply Voltage
Ground
SOP
21
20
19
18
17
16
15
Top View
August 15, 2006
STK Control #ML0051
1
Rev 1.1
SIMTEK [ SIMTEK CORPORATION ]
