1
November 01, 2001
U635H16
PowerStore
2K x 8 nvSRAM
Pin Configuration
Pin Description
Signal Name
Signal Description
A0 - A10
DQ0 - DQ7
Address Inputs
Data In/Out
Chip Enable
Output Enable
Write Enable
Power Supply Voltage
Ground
E
G
W
VCC
VSS
High-performance CMOS non-
volatile static RAM 2048 x 8 bits
25, 35 and 45 ns Access Times
12, 20 and 25 ns Output Enable
Access Times
I
CC
= 15 mA at 200 ns Cycle Time
Automatic STORE to EEPROM
on Power Down using system
capacitance
Software initiated STORE
(STORE Cycle Time < 10 ms)
Automatic STORE Timing
10
5
STORE cycles to EEPROM
10 years data retention in
EEPROM
Automatic RECALL on Power Up
Software RECALL Initiation
(RECALL Cycle Time < 20
μ
s)
Unlimited RECALL cycles from
EEPROM
Single 5 V
±
10 % Operation
Operating temperature ranges:
0 to 70
-40 to 85
CECC 90000 Quality Standard
ESD characterization according
MIL STD 883C M3015.7-HBM
(classification see IC Code
Numbers)
Packages:PDIP24 (600 mil)
SOP24 (300 mil)
°
C
°
C
The U635H16 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 U635H16 is a fast static RAM
(25, 35, 45 ns), with a nonvolatile
electrically
erasable
(EEPROM) element incorporated
in each static memory cell. The
SRAM can be read and written an
unlimited number of times, while
independent nonvolatile data resi-
des in EEPROM. Data transfers
from the SRAM to the EEPROM
(the STORE operation) take place
automatically upon power down
using charge stored in system
capacitance.
Transfers from the EEPROM to the
SRAM (the RECALL operation)
take place automatically on power
up. The U635H16 combines the
high performance and ease of use
of a fast SRAM with nonvolatile
data integrity.
PROM
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.
Features
Top View
2
3
4
5
6
7
8
9
A6
A5
A4
A3
A2
A1
A0
A8
A9
W
G
A10
E
DQ7
DQ6
23
22
21
20
19
18
17
16
1
A7
VCC
24
10
11
12
DQ1
DQ2
VSS
DQ5
DQ4
DQ3
15
14
13
DQ0
PDIP
SOP
24
Description