AT27C256R
Features
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Fast Read Access Time - 45 ns
Low Power CMOS Operation
100
µA
max. Standby
20 mA max. Active at 5 MHz
JEDEC Standard Packages
28-Lead 600-mil PDIP
32-Lead PLCC
28-Lead TSOP and SOIC
5V
±
10% Supply
High Reliability CMOS Technology
2,000V ESD Protection
200 mA Latchup Immunity
Rapid
™
Programming Algorithm - 100
µs/byte
(typical)
CMOS and TTL Compatible Inputs and Outputs
Integrated Product Identification Code
Commercial and Industrial Temperature Ranges
256K (32K x 8)
OTP
CMOS
EPROM
Description
The AT27C256R is a low-power, high performance 262,144 bit one-time programma-
ble read only memory (OTP EPROM) organized 32K by 8 bits. It requires only one
5V power supply in normal read mode operation. Any byte can be accessed in less
than 45 ns, eliminating the need for speed reducing WAIT states on high performance
microprocessor systems.
Atmel’s scaled CMOS technology provides low active power consumption, and fast
programming. Power consumption is typically only 8 mA in Active Mode and less
than 10
µA
in Standby.
(continued)
Pin Configurations
Pin Name
A0 - A14
O0 - O7
CE
OE
NC
Function
Addresses
Outputs
Chip Enable
Output Enable
No Connect
PDIP, SOIC Top View
AT27C256R
PLCC Top View
TSOP Top View
Type 1
Note: PLCC Package Pins 1 and
17 are DON’T CONNECT.
0014G
3-125
Description
(Continued)
The AT27C256R is available in a choice of industry stand-
ard JEDEC-approved one time programmable (OTP)
plastic DIP, PLCC, SOIC, and TSOP packages. All de-
vices feature two-line control (CE, OE) to give designers
the flexibility to prevent bus contention.
With 32K byte storage capability, the AT27C256R allows
firmware to be stored reliably and to be accessed by the
system without the delays of mass storage media.
Atmel’s 27C256R has additional features to ensure high
quality and efficient production use. The Rapid
™
Program-
ming Algorithm reduces the time required to program the
part and guarantees reliable programming. Programming
time is typically only 100
µs/byte.
The Integrated Product
Identification Code electronically identifies the device and
manufacturer. This feature is used by industry standard
programming equipment to select the proper program-
ming algorithms and voltages.
System Considerations
Switching between active and standby conditions via the
Chip Enable pin may produce transient voltage excur-
sions. Unless accommodated by the system design, these
transients may exceed data sheet limits, resulting in de-
vice non-conformance. At a minimum, a 0.1
µF
high fre-
quency, low inherent inductance, ceramic capacitor
should be utilized for each device. This capacitor should
be connected between the V
CC
and Ground terminals of
the device, as close to the device as possible. Additionally,
to stabilize the supply voltage level on printed circuit
boards with large EPROM arrays, a 4.7
µF
bulk electrolytic
capacitor should be utilized, again connected between the
V
CC
and Ground terminals. This capacitor should be posi-
tioned as close as possible to the point where the power
supply is connected to the array.
3-126
AT27C256R
AT27C256R
Block Diagram
Absolute Maximum Ratings*
Temperature Under Bias ................ -55°C to +125°C
Storage Temperature...................... -65°C to +150°C
Voltage on Any Pin with
Respect to Ground......................... -2.0V to +7.0V
(1)
Voltage on A9 with
Respect to Ground ...................... -2.0V to +14.0V
(1)
V
PP
Supply Voltage with
Respect to Ground....................... -2.0V to +14.0V
(1)
*NOTICE: Stresses beyond those listed under “Absolute Maxi-
mum Ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of the
device at these or any other conditions beyond those indi-
cated in the operational sections of this specification is not
implied. Exposure to absolute maximum rating conditions
for extended periods may affect device reliability.
Note:
1. Minimum voltage is -0.6V dc which may undershoot
to -2.0V for pulses of less than 20 ns. Maximum out-
put pin voltage is V
CC
+ 0.75V dc which may over-
shoot to +7.0V for pulses of less than 20 ns.
Operating Modes
Mode \ Pin
Read
Output Disable
Standby
Rapid Program
(2)
PGM Verify
(2)
Optional PGM Verify
(2)
PGM Inhibit
(2)
Product Identification
(4)
CE
V
IL
V
IL
V
IH
V
IL
X
(1)
V
IL
V
IH
V
IL
OE
V
IL
V
IH
X
(1)
V
IH
V
IL
V
IL
V
IH
V
IL
Ai
Ai
X
(1)
X
(1)
Ai
Ai
Ai
X
(1)
A9 = V
H (3)
A0 = V
IH
or V
IL
A1 - A14 = V
IL
V
PP
V
CC
V
CC
V
CC
V
PP
V
PP
V
CC
V
PP
V
CC
Outputs
D
OUT
High Z
High Z
D
IN
D
OUT
D
OUT
High Z
Identification
Code
Notes: 1. X can be V
IL
or V
IH
.
2. Refer to Programming characteristics.
3. V
H
= 12.0
±
0.5V.
4. Two identifier bytes may be selected. All Ai inputs
are held low (V
IL
), except A9 which is set to V
H
and A0
which is toggled low (V
IL
) to select the Manufacturer’s Identi-
fication byte and high (V
IH
) to select the Device Code byte.
3-127
DC and AC Operating Conditions for Read Operation
AT27C256R
-45
Operating
Temp. (Case)
V
CC
Supply
Com.
0°C - 70°C
5V
±
10%
Ind. -40°C - 85°C
-55
0°C - 70°C
-40°C - 85°C
5V
±
10%
-70
0°C - 70°C
-40°C - 85°C
5V
±
10%
-90
0°C - 70°C
-40°C - 85°C
5V
±
10%
-12
0°C - 70°C
-40°C - 85°C
5V
±
10%
-15
0°C - 70°C
-40°C - 85°C
5V
±
10%
DC and Operating Characteristics for Read Operation
Symbol
I
LI
I
LO
I
PP1
(2)
I
SB
I
CC
V
IL
V
IH
V
OL
V
OH
Parameter
Input Load Current
Output Leakage Current
Condition
V
IN
= 0V to V
CC
V
OUT
= 0V to V
CC
I
SB1
(CMOS), CE = V
CC
±
0.3V
I
SB2
(TTL), CE = 2.0 to V
CC
+ 0.5V
V
CC
Active Current
Input Low Voltage
Input High Voltage
Output Low Voltage
Output High Voltage
I
OL
= 2.1 mA
I
OH
= -400
µA
2.4
f = 5 MHz, I
OUT
= 0 mA,
CE = V
IL
-0.6
2.0
Min
Max
±1
±5
10
100
1
20
0.8
V
CC
+ 0.5
0.4
Units
µA
µA
µA
µA
mA
mA
V
V
V
V
V
PP
(1)
Read/Standby Current V
PP
= V
CC
V
CC
(1)
Standby Current
Notes: 1. V
CC
must be applied simultaneously or before V
PP
,
and removed simultaneously or after V
PP
.
2. V
PP
may be connected directly to V
CC
, except during program-
ming. The supply current would then be the sum of I
CC
and I
PP
.
AC Characteristics for Read Operation
AT27C256R
-45
Symbol
t
ACC (3)
t
CE (2)
t
OE (2, 3)
t
DF (4, 5)
t
OH
Notes:
-55
Min
Max
-70
Min
Max
-90
Min
Max
-12
Min
Max
-15
Min
Max
Parameter
Address to
Output Delay
CE to Output Delay
OE to Output Delay
Condition
CE = OE
= V
IL
OE = V
IL
CE = V
IL
Min
Max
Units
ns
ns
ns
ns
ns
45
45
20
20
7
7
55
55
25
20
7
70
70
30
25
0
90
90
30
25
0
120
120
35
30
0
150
150
40
35
OE or CE High to
Output Float, whichever occurred first
Output Hold from
Address, CE or OE,
whichever occurred first
2, 3, 4, 5. - see AC Waveforms for Read Operation.
3-128
AT27C256R
AT27C256R
AC Waveforms for Read Operation
(1)
Notes: 1. Timing measurement reference level is 1.5V for -45
and -55 devices. Input AC drive levels are V
IL
=
0.0V and V
IH
= 3.0V. Timing measurement refer-
ence levels for all other speed grades are V
OL
=
0.8V and V
OH
= 2.0V. Input AC drive levels are V
IL
= 0.45V and V
IH
= 2.4V.
2. OE may be delayed up to t
CE
- t
OE
after the falling
edge of CE without impact on t
CE
.
3. OE may be delayed up to t
ACC
- t
OE
after the address is valid
without impact on t
ACC
.
4. This parameter is only sampled and is not 100% tested.
5. Output float is defined as the point when data is no longer
driven.
Input Test Waveforms and Measurement Levels
For -45 and -55 devices only:
Output Test Load
t
R
, t
F
< 5 ns (10% to 90%)
For -70, -90, -12, and -15 devices:
Note:
C
L
= 100 pF including jig
capacitance, except for
the -45 and -55 devices,
where C
L
= 30 pF.
t
R
, t
F
< 20 ns (10% to 90%)
Pin Capacitance
(f = 1MHz, T = 25°C)
Typ
C
IN
C
OUT
Note:
(1)
Max
6
12
Units
pF
pF
Conditions
V
IN
= 0V
V
OUT
= 0V
4
8
1. Typical values for nominal supply voltage. This parameter is only sampled and is not 100% tested.
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