M27C64A

64 Kbit (8Kb x 8) UV EPROM and OTP EPROM

March 1998

1/12

10% SUPPLY VOLTAGE in READ

OPERATION
FAST ACCESS TIME: 150ns
LOW POWER "CMOS" CONSUMPTION:
Active Current 30mA
Standby Current 100

PROGRAMMING VOLTAGE: 12.5V

0.25V

HIGH SPEED PROGRAMMING
(less than 1 minute)
ELECTRONIC SIGNATURE
Manufacturer Code: 9Bh
Device Code: 08h

DESCRIPTION

The M27C64A is a 64Kbit EPROM offered in the
two ranges UV (ultra violet erase) and OTP (one
time programmable). It is ideally suited for micro-
processor systems requiring large programs and is
organized as 8,192 by 8 bits.

The FDIP28W (window ceramic frit-seal package)
has transparent lid which allows the user to expose
the chip to ultraviolet light to erase the bit pattern.
A new pattern can then be written to the device by
following the programming procedure.

For applications where the content is programmed
only on time and erasure is not required, the
M27C64A is offered in PLCC32 package.

AI00834B

A0-A12

Q0-Q7

VPP

VCC

M27C64A

VSS

Figure 1. Logic Diagram

A0-A12

Address Inputs

Q0-Q7

Data Outputs

Chip Enable

Output Enable

Program

Program Supply

Supply Voltage

Ground

Table 1. Signal Names

PLCC32 (C)

FDIP28W (F)

VSS

A10

A11

A12

VPP

VCC

AI00835

M27C64A

Figure 2A. DIP Pin Connections

Warning: NC = Not Connected

AI00836

A10

A11

M27C64A

A12

Figure 2B. LCC Pin Connections

Warning: NC = Not Connected, DU = Don't Use

Symbol

Parameter

Value

Unit

Ambient Operating Temperature

(3)

40 to 125

BIAS

Temperature Under Bias

50 to 125

STG

Storage Temperature

65 to 150

(2)

Input or Output Voltages (except A9)

2 to 7

Supply Voltage

2 to 7

(2)

A9 Voltage

2 to 13.5

Program Supply Voltage

2 to 14

Notes: 1. Except for the rating "Operating Temperature Range", stresses above those listed in the Table "Absolute Maximum Ratings"

may cause permanent damage to the device. These are stress ratings only and operation of the device at these or any other
conditions above those indicated in the Operating sections of this specification is not implied. Exposure to Absolute Maximum
Rating conditions for extended periods may affect device reliability. Refer also to the STMicroelectronics SURE Program and other
relevant quality documents.

2. Minimum DC voltage on Input or Output is 0.5V with possible undershoot to 2.0V for a period less than 20ns. Maximum DC

voltage on Output is V

+0.5V with possible overshoot to V

+2V for a period less than 20ns.

3. Depends on range.

Table 2. Absolute Maximum Ratings

(1)

DEVICE OPERATION
The modes of operation of the M27C64A are listed
in the Operating Modes table. A single power sup-
ply is required in the read mode. All inputs are TTL
levels except for V

and 12V on A9 for Electronic

Signature.

Read Mode
The M27C64A has two control functions, both of
which must be logically active in order to obtain
data at the outputs. Chip Enable (E) is the power
control and should be used for device selection.
Output Enable (G) is the output control and should

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M27C64A

be used to gate data to the output pins, inde-
pendent of device selection. Assuming that the
addresses are stable, the address access time
(t

AVQV

) is equal to the delay from E to output (t

ELQV

Data is available at the output after a delay of t

GLQV

from the falling edge of G, assuming that E has
been low and the addresses have been stable for
at least t

AVQV

-t

GLQV

Standby Mode

The M27C64A has a standby mode which reduces
the active current from 30mA to 100

A. The

M27C64A is placed in the standby mode by apply-
ing a CMOS high signal to the E input. When in the
standby mode, the outputs are in a high impedance
state, independent of the G input.

Two Line Output Control

Because EPROMs are usually used in larger mem-
ory arrays, this product features a 2 line control
function which accommodates the use of multiple
memory connection. The two line control function
allows:

a. the lowest possible memory power dissipation,

b. complete assurance that output bus contention

will not occur.

For the most efficient use of these two control lines,
E should be decoded and used as the primary
device selecting function, while G should be made
a common connection to all devices in the array
and connected to the READ line from the system

control bus. This ensures that all deselected mem-
ory devices are in their low power standby mode
and that the output pins are only active when data
is required from a particular memory device.
System Considerations
The power switching characteristics of Advanced
CMOS EPROMs require careful decoupling of the
devices. The supply current, I

, has three seg-

ments that are of interest to the system designer:
the standby current level, the active current level,
and transient current peaks that are produced by
the falling and rising edges of E. The magnitude of
the transient current peaks is dependent on the
capacitive and inductive loading of the device at the
output.
The associated transient voltage peaks can be
suppressed by complying with the two line output
control and by properly selected decoupling ca-
pacitors. It is recommended that a 0.1

F ceramic

capacitor be used on every device between V

and V

. This should be a high frequency capacitor

of low inherent inductance and should be placed
as close to the device as possible. In addition, a
4.7

F bulk electrolytic capacitor should be used

between V

and V

for every eight devices. The

bulk capacitor should be located near the power
supply connection point. The purpose of the bulk
capacitor is to overcome the voltage drop caused
by the inductive effects of PCB traces.

Mode

Q0 - Q7

Read

Data Out

Output Disable

Hi-Z

Program

Pulse

Data In

Verify

Data Out

Program Inhibit

Hi-Z

Standby

Hi-Z

Electronic Signature

Codes

Note: X = V

or V

, V

= 12V

0.5V

Table 3. Operating Modes

Identifier

Hex Data

Manufacturer's Code

9Bh

Device Code

08h

Table 4. Electronic Signature

3/12

M27C64A

Programming
When delivered (and after each erasure for UV
EPROM), all bits of the M27C64A are in the "1"
state. Data is introduced by selectively program-
ming "0"s into the desired bit locations. Although
only "0"s will be programmed, both "1"s and "0"s
can be present in the data word. The only way to
change a "0" to a "1" is by die exposition to ultra-
violet light (UV EPROM). The M27C64A is in the
programming mode when V

input is at 12.5V, E

is at V

and P is pulsed to V

. The data to be

programmed is applied to 8 bits in parallel to the
data output pins. The levels required for the ad-
dress and data inputs are TTL. V

is specified to

be 6V

0.25V.

High Speed Programming
The high speed programming algorithm, described
in the flowchart, rapidly programs the M27C64A
using an efficient and reliable method, particularly
suited to the production programming environ-
ment. An individual device will take around 1 minute
to program.
Program Inhibit
Programming of multiple M27C64A in parallel with
different data is also easily accomplished. Except
for E, all like inputs including G of the parallel
M27C64A may be common. A TTL low level pulse
applied to a M27C64A P input, with E low and V

at 12.5V, will program that M27C64A. A high level

E input inhibits the other M27C64A from being
programmed.

Program Verify

A verify (read) should be performed on the pro-
grammed bits to determine that they were correctly
programmed. The verify is accomplished with E
and G at V

, P at V

, V

at 12.5V and V

at 6V.

Electronic Signature

The Electronic Signature (ES) mode allows the
reading out of a binary code from an EPROM that
will identify its manufacturer and type. This mode
is intended for use by programming equipment to
automatically match the device to be programmed
with its corresponding programming algorithm. The
ES mode is functional in the 25

C ambient

temperature range that is required when program-
ming the M27C64A. To activate the ES mode, the
programming equipment must force 11.5V to 12.5V
on address line A9 of the M27C64A, with
V

=5V. Two identifier bytes may then be

sequenced from the device outputs by toggling
address line A0 from V

to V

. All other address

lines must be held at V

during Electronic Signa-

ture mode.

Byte 0 (A0=V

) represents the manufacturer code

and byte 1 (A0=V

) the device identifier code. For

the STMicroelectronics M27C64A, these two iden-
tifier bytes are given in Table 4 and can be read-out
on outputs Q0 to Q7.

4/12

M27C64A

AI00826

2.4V

0.4V

2.0V

0.8V

Figure 3. AC Testing Input Output Waveforms

Input Rise and Fall Times

20ns

Input Pulse Voltages

0.4V to 2.4V

Input and Output Timing Ref.
Voltages

0.8V to 2.0V

AC MEASUREMENT CONDITIONS

AI00828

1.3V

OUT

CL = 100pF

CL includes JIG capacitance

3.3k

1N914

DEVICE

UNDER

TEST

Figure 4. AC Testing Load Circuit

Note that Output Hi-Z is defined as the point where data
is no longer driven.

Symbol

Parameter

Test Condition

Min

Max

Unit

Input Capacitance

= 0V

OUT

Output Capacitance

OUT

= 0V

Note: 1. Sampled only, not 100% tested.

Table 5. Capacitance

(1)

= 25

C, f = 1 MHz )

AI00778B

tAXQX

tEHQZ

A0-A12

Q0-Q7

tAVQV

tGHQZ

tGLQV

tELQV

VALID

Hi-Z

VALID

Figure 5. Read Mode AC Waveforms

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M27C64A

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