AT28C64X-25SC EEPROM Equivalent & Substitute Parts

Part Overview

The AT28C64X-25SC is a 64Kbit parallel EEPROM memory IC manufactured by Microchip Technology in a 28-SOIC package. This component is classified as obsolete, which necessitates identification of functionally equivalent alternatives for ongoing system support and new designs. The part operates with a 250 ns access time and supports standard 4.5V to 5.5V supply voltage across a 0°C to 70°C operating temperature range.

Key Parameters

Parameter	Value
Memory Size	64Kbit
Memory Organization	8K x 8
Memory Interface	Parallel
Access Time	250 ns
Voltage Supply	4.5V ~ 5.5V
Operating Temperature	0°C ~ 70°C
Package / Case	28-SOIC (0.295", 7.50mm Width)
Mounting Type	Surface Mount
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the AT28C64X-25SC is determined by the following critical parameters: memory capacity (64Kbit), memory organization (8K x 8), parallel interface architecture, identical package form factor (28-SOIC), and compatible supply voltage range (4.5V ~ 5.5V). Access time, write cycle time, and operating temperature range may vary within acceptable limits for most applications, provided the substitute part meets or exceeds the performance envelope of the original component. All identified substitutes maintain the same pinout and electrical interface characteristics required for direct replacement.

Parameter Comparison

Parameter	AT28C64X-25SC	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	250 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	0°C ~ 70°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	0°C ~ 70°C
Package / Case	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

All substitute parts listed maintain functional equivalence with the AT28C64X-25SC through identical memory capacity, organization, and parallel interface architecture within the same 28-SOIC package footprint.

AT28C64B-15SU is an active Microchip Technology product offering improved access time (150 ns) and extended operating temperature range (-40°C to 85°C) compared to the original part. This substitute carries ROHS3 compliance certification and is available in tube packaging with verified programmability status.

X28HC64SIZ-12, X28HC64SIZ-12T1, and X28HC64SZ-12 are Renesas Electronics alternatives providing superior access time performance (120 ns) and extended temperature operating range (-40°C to 85°C for the first two variants). X28HC64SZ-12 maintains the original 0°C to 70°C temperature specification. All three Renesas variants carry ROHS3 compliance. X28HC64SIZ-12T1 is supplied in tape and reel packaging, while X28HC64SZ-12 is available in tube format.

Selection between Microchip and Renesas alternatives depends on supply chain availability, packaging requirements, and temperature range specifications for the target application.

Frequently Asked Questions (FAQ)

Q: Can AT28C64B-15SU directly replace AT28C64X-25SC in existing designs?

A: Yes. Both parts share identical memory capacity (64Kbit), organization (8K x 8), parallel interface, and 28-SOIC package form factor. The substitute offers faster access time (150 ns vs. 250 ns) and extended operating temperature range, making it functionally compatible for direct substitution.

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

A: Both parts are functionally identical with 120 ns access time and 64Kbit capacity. The primary difference is packaging: X28HC64SIZ-12 uses standard tube packaging, while X28HC64SIZ-12T1 is supplied in tape and reel format for automated assembly processes.

Q: Are all substitute parts RoHS compliant?

A: All listed substitutes carry ROHS3 compliance certification. The original AT28C64X-25SC is RoHS non-compliant due to its obsolete status.

Q: Does operating temperature range affect substitution compatibility?

A: Operating temperature range does not prevent substitution if the substitute range encompasses or exceeds the original specification. AT28C64B-15SU and the Renesas X28HC64 variants offer extended temperature ranges (-40°C to 85°C) compared to the original 0°C to 70°C specification, providing additional design margin for temperature-sensitive applications.

Q: What is the significance of access time differences between substitutes?

A: All substitutes provide equal or faster access time than the original 250 ns specification. Faster access times (150 ns for AT28C64B-15SU, 120 ns for Renesas variants) represent performance improvements and do not create compatibility issues in designs originally specified for 250 ns operation.

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