LOW VOLTAGE CMOS

256K ELECTRICALLY ERASABLE PROGRAMMABLE ROM

32K X 8 BIT EEPROM

ADDRESSES (A0 - A14)
The Addresses are used to select an 8 bits
memory location during a write or read opera-
tion.

OUTPUT ENABLE (OE)
The Output Enable input activates the output buff-
ers during the read operations.

CHIP ENABLES (CE)
The Chip Enable input must be low to enable all
read/write operation on the device. By setting CE
high, the device is disabled and the power con-
sumption is extremely low with the standby cur-
rent below 35 µA.

FEATURES:
·

200 ns Access Time

Automatic Page Write Operation

Internal Control Timer
Internal Data and Address Latches for 64 Bytes

Fast Write Cycle Times

Byte or Page Write Cycles: 10 ms
Time to Rewrite Complete Memory: 5 sec
Typical Byte Write Cycle Time: 160 µsec

Software Data Protection

Low Power Dissipation

20 mA Active Current
35 µA CMOS Standby Current

Direct Microprocessor End of Write Detection

Data Polling

High Reliability CMOS Technology with Self Redundant
EEPROM Cell

Typical Endurance: 100,000 Cycles
Data Retention: 10 Years

TTL and CMOS Compatible Inputs and Outputs

Single 3.3 V ± 10% Power Supply for Read and
Programming Operations

JEDEC Approved Byte-Write Pinout

DESCRIPTION:

The Turbo IC 28LV256 is a 32K X 8 EEPROM fabricated
with Turbo's proprietary, high reliability, high performance
CMOS technology. The 256K bits of memory are organized
as 32K by 8 bits. The device offers access time of 200 ns
with power dissipation below 66 mW.

The 28LV256 has a 64-bytes page write operation, enabling
the entire memory to be typically written in less than 5.0
seconds. During a write cycle, the address and 1 to 64 bytes
of data are internally latched, freeing the address and data
bus for other microprocessor operations. The programming
process is automatically controlled by the device using an
internal control timer. Data polling on one or all I/O can be
used to detect the end of a programming cycle. In addition,
the 28LV256 includes an user-optional software data write
mode offering additional protection against unwanted (false)
write. The device utilizes an error protected self redundant
cell for extended data retention and endurance.

WRITE ENABLE (WE)
The Write Enable input initiates the writing of data
into the memory.

DATA INPUT/OUTPUT (I/O0-I/O7)
Data Input/Output pins are used to read data out
of the memory or to write Data into the memory.

PIN DESCRIPTION

Turbo IC, Inc.

28LV256

A11

A10

I/O7

I/O6

I/O0

I/O1

I/O2

GND

I/O3

I/O4

I/O5

A12

A14

VCC

A13

32 pins PLCC

A14

A12

I/O0

I/O1

I/O2

GND

VCC

A13

A11

A10

I/O7

I/O6

I/O5

I/O4

I/O3

A14

A12

I/O0

I/O1

I/O2

GND

VCC

A13

A11

A10

I/O7

I/O6

I/O5

I/O4

I/O3

A10

I/O7

I/O5

I/O3

I/O2

I/O0

I/O1

GND

I/O4

I/O6

A13

VCC

A12

A14

A11

28 pins PDIP

28 pins SOIC (SOG)

28 pins TSOP

22
21

DEVICE OPERATION

READ:
The 28LV256 is accessed like a static RAM. Read operations are initi-
ated by both CE and OE going low and terminated by either CE or OE
returning high. The outputs are at the high impedance state whenever
CE or OE returns high. The two line control architecture gives designers
flexibility in preventing bus contention.
WRITE:
A write cycle is initiated when CE and WE are low and OE is high. The
address is latched internally on the falling edge of CE or WE whichever
occurs last. The data is latched by the rising edge of CE or WE whichever
occurs first. Once a byte write cycle has been started, the internal timer
automatically generates the write sequence to the completion of the write
operation.
PAGE WRITE OPERATION:
The page write operation of 28LV256 allows one to 64 bytes of data to be
serially loaded into the device and then simultaneously written into memory
during the internally generated write cycle. After the first byte has been
loaded, successive bytes of data may be loaded until the full page of 64
bytes is loaded. Each new byte to be written must be loaded within 200
µs of the previously loaded byte. The page address defined by the ad-
dresses A6-A14 is latched by the first CE or WE falling edge which ini-
tiates a writing cycle and they will stay latched until the completion of the
page write. Any changes in the page addresses during the load-write
cycle will not affect the initially latched page addresses. Addresses A0 -
A5 are used to define which bytes will be loaded and written within the 64
bytes page. The bytes may be loaded in any order that is convenient to
the user. The content of a loaded byte may be altered at any time during
the loading cycle if the maximum allowed byte-load time (200 µs) is not
exceeded. Only loaded bytes within the page will be written; no rewriting
will occur to the non-selected bytes in the page.
DATA POLLING:
The 28LV256 features DATA POLLING to indicate the completion of a
write cycle to the host system. During a byte or page write cycle, an
attempted read of the last byte loaded into the page will result in the
complement of the loaded byte on all outputs I/O0 - I/O7 (i.e. loaded data
01010110, read data 10101001). Data Polling feature may be used by an
attempted read on one or more outputs (whatever is convenient for the
system developer). Once the write cycle has been completed, true data
is valid on all outputs and the next cycle may be started.
DATA PROTECTION:
The 28LV256 has three hardware features to protect the written content
of the memory against inadvertent writes :

a.)

Vcc threshold detector: If Vcc is below 2.5 V, the write capa-

bilities of the chip is inhibited for whatever input conditions.
b.)

Noise protection: A WE, OE, or CE pulse less than 10 ns in

width is not able to initiate a write cycle.
c.)

Write inhibit: Holding OE at low, or CE at high, or WE at high

inhibits the write cycle.

SOFTWARE WRITE PROTECTION:
The 28LV256 offers a software controlled data write protection feature.
The device is delivered to the user with the software data write protection
DISABLED; i.e. the device will go to the data write operation as long as
Vcc exceeds 2.5 V and CE, WE, and OE inputs are set at write mode
levels. The 28LV256 can be automatically protected against an accidental
write operation during power-up or power-down without any external cir-
cuitry by enabling the software data write protection features. This features
is enabled after the first write cycle which includes the software algorithm.
After this operation is done, the data write function of the device may be
performed only if every page write cycle is preceded by the software algo-
rithm. The device will maintain its software protect feature for the rest of its
life unless that the software algorithm for disabling the protection is imple-
mented.
SOFTWARE ALGORITHM:
The 28LV256 has an internal register for the software algorithm which en-
ables the memory to provide the user with additional features:

a.) Software Write Protect Enable

A sequence of three dummy data writes to the memory will activate
internal EEPROM fuses during the first page write cycle. These EE-
PROM fuses will reject any write attempts of new pages of data
unless the three dummy data writes are repeated at the beginning of
any page writes. The timing for the dummy data and addresses must
be the same as for a normal write operation. A violation of the three
steps write protect sequence in data or address timing and content
will abort the procedure and reset the device to the starting point
condition.

Note: After the three dummy data writes, at least one page load/
write cycle must be performed. If no additional page data is added
to the three dummy data writes, the software write protect will
not be enabled until the next write, which will not be protected.
Table 1 shows the required procedure for enabling the software write
protect:

Step

Mode

Address A14-A0

Data I/O 7-0

Page Write

5555 Hex

AA Hex

Page Write

2AAA Hex

55 Hex

Page Write

5555 Hex

A0 Hex

4-67

Page Write

Address

Data

b.) Software Write Protect Disable

The software algorithm of 28LV256 includes a six steps sequence of
dummy data writing to disable the software write protect feature de-
scribed in a.). The six steps write sequence shown in Table 2 must
be performed at the beginning of a page write cycle. A violation of
the six steps write sequence in data or address timing and content
will abort the procedure and reset the chip to the starting point con-
dition. After a page write cycle including the six steps write sequence
has been performed, the 28LV256 does not require the use of three
dummy data writes described in a.) for the following page write cycle.
The device is at the software write protect disabled state.

Note: After the six dummy data writes, at least one page load/
write cycle must be performed. If no additional page data is added
to the six dummy data writes, the software write protect disable
will not be activated. Table 2 shows the required procedure for dis-
abling the software write protect:

Step

Mode

Address A14-A0

Data I/O 7-0

Page Write

5555 Hex

AA Hex

Page Write

2AAA Hex

55 Hex

Page Write

5555 Hex

80 Hex

Page Write

5555 Hex

AA Hex

Page Write

2AAA Hex

55 Hex

Page Write

5555 Hex

20 Hex

7-70

Page Write

Address

Data

c.) Software Chip Clear

The software algorithm of 28LV256 includes a sequence of six steps
dummy data writing to perform a chip clear operation. Table 3 shows
the six steps write sequence to perform the software chip clear op-
eration:

Step

Mode

Address A14-A0

Data I/O 7-0

Page Write

5555 Hex

AA Hex

Page Write

2AAA Hex

55 Hex

Page Write

5555 Hex

80 Hex

Page Write

5555 Hex

AA Hex

Page Write

2AAA Hex

55 Hex

Page Write

5555 Hex

10 Hex

At the end of the six steps write sequence shown in Table 3, the
device automatically activates its internal timer to control the chip

Turbo IC, Inc.

28LV256

erase cycle; typically takes 20 msec. After a software chip clear op-
eration has been completed, all 256K bit locations of memory show
high level at read operation mode.

d.) Software Autoclear Disable Mode

This software algorithm disables the internal automatic clear before
write cycle. Table 4 shows the six steps needed to perform the auto-
clear disable mode:

Step

Mode

Address A14-A0

Data I/O 7-0

Page Write

5555 Hex

AA Hex

Page Write

2AAA Hex

55 Hex

Page Write

5555 Hex

80 Hex

Page Write

5555 Hex

AA Hex

Page Write

2AAA Hex

55 Hex

Page Write

5555 Hex

40 Hex

7-70

Page Write

Address

Data

Page write operation using the software autoclear disable mode will
reduce programming time to typically 5 msec. The page write using
software autoclear disable mode is usually used after a chip clear or
a software chip clear operation. At the end of the six steps sequence,
the autoclear before write is disabled and will stay that way unless a
power-down occurs or the software autoclear enable procedure is
initiated.

e.) Software Autoclear Enable Mode

Automatic page clear before page write can be restored to 28LV256
either by Vcc power-down or by software autoclear enable mode.
Table 5 shows the six steps page write procedure needed to enable
software autoclear mode:

Step

Mode

Address A14-A0

Data I/O 7-0

Page Write

5555 Hex

AA Hex

Page Write

2AAA Hex

55 Hex

Page Write

5555 Hex

80 Hex

Page Write

5555 Hex

AA Hex

Page Write

2AAA Hex

55 Hex

Page Write

5555 Hex

50 Hex

7-70

Page Write

Address

Data

Symbol Parameter

Condition

Min

Max Units

Icc

Active Vcc

CE=OE=Vil; All I/O

20 (C)

Current

Open, Min Read or

30 (I)

Write Cycle Time

50 (M)

Isb1

CMOS

CE=Vcc-0.3 V to

35 (C)

µA

Standby

Vcc+1 V

50 (I&M) µA

Current

Iil

Input

µA

Leakage
Current

Iol

Output

µA

Leakage
Current

Vil

Input Low

-0.1

-0.6

Voltage

Vih

Input High

1.8 Vcc+0.3

Voltage

Vol

Output Low

Iol=1.6 mA

0.3

Voltage

Voh

Output High

Ioh=-0.1 mA

1.8

Voltage

D.C. CHARACTERISTICS

= INDUSTRIAL

(M) = MILITARY

Turbo IC, Inc.

28LV256

ABSOLUTE MAXIMUM STRESS RANGES *

TEMPERATURE
Storage:

-65°

C to 150° C

Under Bias:

-55° C to 125° C

ALL INPUT OR OUTPUT VOLTAGES
with respect to Vss

+6 V to -0.3 V

"Absolute Maximum Ratings" may cause perma-
nent damage to the device. This is a stress rating
only and functional operation of the device at
these or any other conditions above those indi-
cated in the operation section of this specifica-
tion is not implied. Exposure to absolute maxi-
mum rating conditions for extended periods may
affect device reliability.

RECOMMENDED OPERATING CONDITIONS

Temperature Range:

Commercial:

C to 70

Industrial:

-40

C to 85

Military:

-55

C to 125

Vcc Supply Voltage:

3.3 V

10%

Endurance:

100,000 Cycles/Byte (Typical)

Data Retention:

10 Years

A.C. CHARACTERISTICS - READ OPERATION

28LV256-3

28LV256-4

28LV256-5

28LV256-6

Symbol

Parameters

Min Max Min Max Min Max Min MaxUnit

tacc

Address to

200

250

300

400 ns

Output Delay

tce

CE to Output

200

250

300

400 ns

Delay

toe

OE to Output

110

150

150 ns

tdf

OE to Output

90 ns

In High Z

toh

Output Hold

from Address
Changes, Chip
Enable or
Output Enable
Whichever
Occurs First

A.C. Read Wave Forms

A.C. TEST CONDITIONS

Output Load : 1 TTL Load and Cl=100 pF
Input Rise and Fall Times : < 10 ns
Input Pulse Level : 0 V to 3 V
Timing Measurement Reference Level : 1.5 V

tacc

ADDRESS VALID

ADDRESS

OUTPUT

HIGH-Z

toe

tce

tdf

toh

OUTPUT VALID

HIGH-Z

TURBO IC PRODUCTS AND DOCUMENTS

All documents are subject to change without notice. Please contact Turbo IC for the latest
revision of documents.

Turbo IC does not assume any responsibility for any damage to the user that may result from
accidents or operation under abnormal conditions.

Turbo IC does not assume any responsibility for the use of any circuitry other than what
embodied in a Turbo IC product. No other circuits, patents, licenses are implied.

Turbo IC products are not authorized for use in life support systems or other critical systems
where component failure may endanger life. System designers should design with error
detection and correction, redundancy and back-up features.

A.C. WRITE CHARACTERISTICS

Symbol Parameter

Min

Max

Units

tas

Address Set-up Time

tah

Address Hold Time

100

tcs

Write Set-up Time

tch

Write Hold Time

tcw

CE Pulse Width

150

twp

WE Pulse Width

150

toes

OE Set-up Time

toeh

OE Hold Time

tds

Data Set-up Time

tdh

Data Hold Time

tblc

Byte Load Cycle

0.2

200

µs

tlp

Last Byte Loaded to Data
Polling Output

500

µs

twc

Write Cycle Time

twc

Write Cycle Time (IND & MIL)

Part Numbers & Order Information
28LV256PC-4

Speed
-3 200 ns
-4 250 ns
-5 300 ns
-6 400 ns

Temperature
C

-Commercial

-Industrial

-Military

Package
J -PLCC
P -PDIP
S -SOIC
T -TSOP

Turbo IC, Inc. 2365 Paragon Drive, Suite I, San Jose, CA 95131 Phone: 408-392-0208 Fax: 408-392-0207

See us at www.turbo-ic.com

32K x 8
EEPROM

Page Mode Write Wave Form

PAGE MODE WRITE CHARACTERISTICS

Symbol Parameter

Min

Max

Unit

twc

Write Cycle Time

tas

Address Set-up Time

tah

Address Hold Time

100

tds

Data Set-up Time

tdh

Data Hold Time

twp

Write Pulse Width

150

tblc

Byte Load Cycle Time

0.2

200

µs

Chip Clear Wave Form

The content of the 28LV256 may be altered to HIGH by the use of the
Chip Clear operation. By setting CE to low, OE to 12 volts, and WE to
low, the entire memory can be cleared (written HIGH) within 20 ms. The
Chip Clear operation is a latch operation mode. After the Chip Clear
starts, the internal chip timer takes over and completes the clear with-
out CE, OE and WE being held active.

A.C. Write Characteristics CE-Controlled

A.C. Write Characteristics WE-Controlled

ADDRESS

DATA

toes

tas

tcs

tah

toeh

tch

twp

tds

tblc

twc

tdh

HIGH-Z

DATA VALID

HIGH-Z

VALID

ADDRESS

DATA

toes

tas

tcs

tah

toeh

tch

twp

tds

tblc

twc

tdh

HIGH-Z

DATA VALID

HIGH-Z

VALID

A0-A5

DATA

twp

tblc

tah

tas

tds

tdh

BYTE-0

BYTE-1

BYTE-2

AD-VALID

ts= 20 ns
tp= 200 ns
th= 20 ns
VH=12.0 V±0.5V

VIH

VIL

VIH

VIL

Turbo IC, Inc.

28LV256

Rev. 3.0 - 10/28/01

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