AT28C64-20SI EEPROM 64Kbit Parallel Memory - Equivalent & Substitute Parts

Part Overview

The AT28C64-20SI is a 64Kbit parallel EEPROM memory IC manufactured by Microchip Technology in a 28-SOIC surface mount package. This component is classified as obsolete, making equivalent substitute parts necessary for ongoing system support and new designs. The part operates with a 200 ns access time and supports standard 4.5V to 5.5V supply voltage across the industrial temperature range of -40°C to 85°C.

Key Parameters

Parameter	Value
Memory Size	64Kbit
Memory Organization	8K x 8
Memory Format	EEPROM
Memory Interface	Parallel
Access Time	200 ns
Write Cycle Time	1 ms
Voltage Supply	4.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package	28-SOIC (0.295", 7.50mm Width)
Mounting Type	Surface Mount

Substitute Part Grouping Explanation

Substitution for the AT28C64-20SI is determined by the following critical parameters:

Memory capacity (64Kbit) and organization (8K x 8)
Parallel interface architecture
Package compatibility (28-SOIC form factor)
Supply voltage range (4.5V ~ 5.5V)
Operating temperature range (-40°C ~ 85°C)

Substitute parts must maintain identical memory specifications and pinout compatibility. Access time and write cycle time may vary, provided the substitute meets or exceeds performance requirements for the target application. All identified substitutes share the same 28-SOIC package and parallel interface, ensuring direct replacement capability at the board level.

Parameter Comparison

Parameter	AT28C64-20SI (Main)	AT28C64B-15SU	X28HC64SIZ-12	X28HC64SIZ-12T1	X28HC64SZ-12
Manufacturer	Microchip Technology	Microchip Technology	Renesas Electronics	Renesas Electronics	Renesas Electronics
Memory Size	64Kbit	64Kbit	64Kbit	64Kbit	64Kbit
Memory Organization	8K x 8	8K x 8	8K x 8	8K x 8	8K x 8
Access Time	200 ns	150 ns	120 ns	120 ns	120 ns
Write Cycle Time	1 ms	10 ms	5 ms	5 ms	5 ms
Voltage Supply	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V	4.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	0°C ~ 70°C
Package	28-SOIC	28-SOIC	28-SOIC	28-SOIC	28-SOIC
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	Non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For applications currently using the AT28C64-20SI, the following selection criteria apply:

AT28C64B-15SU is the manufacturer-recommended direct substitute from Microchip Technology. This part maintains the same memory specifications and package while offering improved access time (150 ns vs. 200 ns) and active product status. It carries ROHS3 compliance and verified programmability certification, making it suitable for new designs and legacy system updates.

X28HC64SIZ-12 and X28HC64SIZ-12T1 are functionally equivalent alternatives from Renesas Electronics Corporation. Both deliver superior access time performance (120 ns) and are available in active production status with ROHS3 compliance. The primary distinction is packaging: X28HC64SIZ-12T1 is supplied in Tape & Reel format, while X28HC64SIZ-12 is supplied in standard packaging. These parts are suitable for applications where faster memory access improves system performance.

X28HC64SZ-12 is a Renesas alternative with identical electrical performance to the X28HC64SIZ variants but operates within a narrower temperature range (0°C ~ 70°C). This part is appropriate only for applications that do not require the full industrial temperature range of the original component.

All substitute parts maintain ROHS3 compliance and are in active production, eliminating obsolescence risk associated with the original AT28C64-20SI.

Frequently Asked Questions (FAQ)

Q: Can the AT28C64B-15SU directly replace the AT28C64-20SI without circuit modifications?

A: Yes. Both parts share identical memory capacity (64Kbit), organization (8K x 8), parallel interface, supply voltage range (4.5V ~ 5.5V), operating temperature range (-40°C ~ 85°C), and 28-SOIC package. The AT28C64B-15SU offers faster access time (150 ns vs. 200 ns), which is a performance improvement with no compatibility issues.

Q: What is the difference between X28HC64SIZ-12 and X28HC64SIZ-12T1?

A: Both parts are electrically and functionally identical with 120 ns access time and 5 ms write cycle time. The difference is packaging: X28HC64SIZ-12T1 is supplied in Tape & Reel format for automated assembly, while X28HC64SIZ-12 is supplied in standard tube packaging. Select based on your assembly process requirements.

Q: Why does X28HC64SZ-12 have a different operating temperature range?

A: X28HC64SZ-12 operates from 0°C to 70°C, compared to the standard industrial range of -40°C to 85°C. This part is suitable only for applications that do not require full industrial temperature coverage. Verify your system's temperature requirements before selection.

Q: Are all substitute parts RoHS compliant?

A: Yes. All identified substitute parts carry ROHS3 compliance certification. The original AT28C64-20SI is RoHS non-compliant. Compliance status should be verified against your procurement and regulatory requirements.

Q: What is the impact of faster access time on system compatibility?

A: Faster access time (150 ns or 120 ns vs. 200 ns) improves memory read performance and is backward compatible with designs specified for the original 200 ns part. No circuit modifications are required. Verify that your system timing specifications do not impose maximum access time limits that would be violated by faster substitutes.

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