Features
•
Fast read access time – 45ns
•
Low-power CMOS operation
•
•
•
•
•
•
•
•
– 100µA max standby
– 20mA max active at 5MHz
JEDEC standard packages
– 28-lead PDIP
– 32-lead PLCC
5V±10% supply
High reliability CMOS technology
– 2,000V ESD protection
– 200mA latchup immunity
Rapid programming algorithm – 100µs/byte (typical)
CMOS- and TTL-compatible inputs and outputs
Integrated product identification code
Industrial and automotive temperature ranges
Green (Pb/halide-free) packaging option
256K (32K x 8)
One-time
Programmable,
Read-only Memory
Atmel AT27C256R
1.
Description
The Atmel
®
AT27C256R is a low-power, high-performance, 262,144-bit, one-time pro-
grammable, read-only memory (OTP EPROM) organized as 32K by 8 bits. It requires only
one 5V power supply in normal read mode operation. Any byte can be accessed in less than
45ns, eliminating the need for speed reducing WAIT states on high-performance micropro-
cessor systems.
The Atmel scaled CMOS technology provides low active power consumption and fast pro-
gramming. Power consumption is typically only 8mA in active mode and less than 10µA in
standby mode.
The AT27C256R is available in a choice of industry-standard, JEDEC-approved, one-time
programmable (OTP) PDIP and PLCC packages. All devices 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.
The AT27C256R has additional features to ensure high quality and efficient production use.
The rapid programming algorithm reduces the time required to program the part and guar-
antees reliable programming. Programming time is typically only 100µs/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 pro-
gramming algorithms and voltages.
0014O–EPROM–10/11
2.
Pin configurations
Pin name
A0 - A14
O0 - O7
CE
OE
NC
Function
Addresses
Outputs
Chip enable
Output enable
No connect
A6
A5
A4
A3
A2
A1
A0
NC
O0
32-lead PLCC
Top view
A7
A12
VPP
NC
VCC
A14
A13
VPP
A12
A7
A6
A5
A4
A3
A2
A1
A0
O0
O1
O2
GND
28-lead PDIP
Top view
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
VCC
A14
A13
A8
A9
A11
OE
A10
CE
O7
O6
O5
O4
O3
Note:
3.
System considerations
Switching between active and standby conditions via the chip enable pin may produce transient voltage excursions. Unless
accommodated by the system design, these transients may exceed datasheet limits, resulting in device non-conformance.
At a minimum, a 0.1µF, high-frequency, 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 4.7µF bulk electrolytic
capacitor should be utilized, again connected between the V
CC
and ground terminals. This capacitor should be positioned as
close as possible to the point where the power supply is connected to the array.
Figure 3-1.
Block diagram
2
Atmel AT27C256R
0014O–EPROM–10/11
O1
O2
GND
NC
O3
O4
O5
14
15
16
17
18
19
20
5
6
7
8
9
10
11
12
13
4
3
2
1
32
31
30
29
28
27
26
25
24
23
22
21
A8
A9
A11
NC
OE
A10
CE
O7
O6
PLCC package pins 1
and 17 are “don’t
connect”
Atmel AT27C256R
4.
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)
Note:
1. Minimum voltage is -0.6V DC, which may undershoot to -2.0V for pulses of less than 20ns. Maximum output pin voltage is
V
CC
+ 0.75V DC, which may overshoot to +7.0V for pulses of less than 20ns.
*NOTICE:
Stresses beyond those listed under “Absolute
maximum 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 indicated in the operational sections of
this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may
affect device reliability.
5.
DC and AC characteristics
Table 5-1.
Mode/Pin
Read
Output disable
Standby
Rapid program
(2)
PGM verify
(2)
Optional PGM verify
(2)
PGM inhibit
(2)
Product identification
(4)
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 tog-
gled low (V
IL
) to select the manufacturer’s identification byte and high (V
IH
) to select the device code byte.
Table 5-2.
DC and AC operating conditions for read operation
Atmel AT27C256R
-45
Operating temp. (case)
Ind.
Auto.
V
CC
supply
5V
±10%
-40C - 85C
-70
-40C - 85C
-40C - 125C
5V
±10%
Operating Modes
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
3
0014O–EPROM–10/11
Table 5-3.
Symbol
I
LI
DC and operating characteristics for read operation
Parameter
Input load current
Condition
Ind.
V
IN
= 0V to V
CC
Auto.
Ind.
Min
Max
±1
±5
±5
±10
10
100
1
20
-0.6
2.0
I
OL
= 2.1mA
I
OH
= -400µA
2.4
0.8
V
CC
+ 0.5
0.4
Units
µA
µA
µA
µA
µA
µA
mA
mA
V
V
V
V
I
LO
I
PP1
(2)
I
SB
I
CC
V
IL
V
IH
V
OL
V
OH
Notes:
Output leakage current
V
PP
(1)
read/standby current
V
CC
(1)
standby current
V
CC
active current
Input low voltage
Input high voltage
Output low voltage
Output high voltage
V
OUT
= 0V to V
CC
V
PP
= V
CC
Auto.
I
SB1
(CMOS), CE = V
CC
0.3V
I
SB2
(TTL), CE = 2.0 to V
CC
+ 0.5V
f = 5MHz, I
OUT
= 0mA, E = V
IL
1. V
CC
must be applied simultaneously with or before V
PP
, and removed simultaneously with or after V
PP
.
2. V
PP
may be connected directly to V
CC
, except during programming. The supply current would then be the sum of I
CC
and
I
PP
.
Table 5-4.
AC characteristics for read operation
Atmel AT27C256R
-45
-70
Max
45
45
20
20
7
7
Min
Max
70
70
30
25
Units
ns
ns
ns
ns
ns
Symbol
t
ACC
(1)
t
CE
(1)
t
OE
(1)
t
DF
(1)
t
OH
Note:
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
OE or CE high to output float, whichever occurred first
Output hold from address, CE or OE, whichever occurred
first
1. See AC waveforms for read operation.
4
Atmel AT27C256R
0014O–EPROM–10/11
Atmel AT27C256R
Figure 5-1.
AC waveforms for read operation
(1)
Notes:
1. Timing measurement reference level is 1.5V for -45 devices. Input AC drive levels are V
IL
= 0.0V and V
IH
= 3.0V. Timing
measurement reference 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.
Figure 5-2.
Input test waveforms and measurement levels
For -45 devices only:
t
R
, t
F
< 5ns (10% to 90%)
For -70 devices:
t
R
, t
F
< 20ns (10% to 90%)
5
0014O–EPROM–10/11
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