AT28HC256F-90TU Equivalent & Substitute Parts

Part Overview

The AT28HC256F-90TU is a 256Kbit parallel EEPROM memory IC manufactured by Microchip Technology, packaged in 28-TSSOP with 90 ns access time. This device is classified as obsolete, making substitute parts necessary for new designs and ongoing production requirements. The part operates across the industrial temperature range of -40°C to 85°C and complies with ROHS3 and REACH standards.

Key Parameters

Parameter	Value
Memory Type	Non-Volatile EEPROM
Memory Size	256Kbit
Memory Organization	32K x 8
Memory Interface	Parallel
Access Time	90 ns
Write Cycle Time	3 ms
Supply Voltage	4.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount

Substitute Part Grouping Explanation

Substitution of the AT28HC256F-90TU is determined by electrical and functional equivalence across the following critical parameters:

Memory capacity and organization (256Kbit, 32K x 8)
Parallel interface architecture
Access time specification (90 ns)
Supply voltage range (4.5V ~ 5.5V)
Operating temperature range (-40°C ~ 85°C)
Non-volatile EEPROM technology
Surface mount mounting type

The AT28HC256F-90SU meets all electrical and functional requirements for direct substitution. The primary difference is packaging format: 28-SOIC versus 28-TSSOP. Both packages are surface mount with compatible pinouts and electrical characteristics.

Parameter Comparison

Parameter	AT28HC256F-90TU (Main)	AT28HC256F-90SU (Substitute)
Manufacturer	Microchip Technology	Microchip Technology
Memory Type	Non-Volatile EEPROM	Non-Volatile EEPROM
Memory Size	256Kbit	256Kbit
Memory Organization	32K x 8	32K x 8
Memory Interface	Parallel	Parallel
Access Time	90 ns	90 ns
Write Cycle Time	3 ms	3 ms
Supply Voltage	4.5V ~ 5.5V	4.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Surface Mount	Surface Mount
Package / Case	28-TSSOP (0.465", 11.80mm Width)	28-SOIC (0.295", 7.50mm Width)
Product Status	Obsolete	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level	3 (168 Hours)	2 (1 Year)

Engineering Selection Recommendations

The AT28HC256F-90SU is the direct electrical equivalent for the obsolete AT28HC256F-90TU. Both devices share identical memory specifications, electrical performance, and operating parameters. Selection between these parts is determined by PCB layout constraints and packaging requirements.

The AT28HC256F-90SU offers the advantage of active product status with current manufacturing support and improved moisture sensitivity rating (MSL 2 versus MSL 3). Both parts maintain ROHS3 compliance and REACH unaffected status.

Package footprint differences require PCB redesign if transitioning from 28-TSSOP to 28-SOIC. The 28-SOIC package is narrower (7.50mm versus 11.80mm), affecting board layout and component spacing.

Frequently Asked Questions (FAQ)

Q: Can AT28HC256F-90SU directly replace AT28HC256F-90TU without circuit modification?

A: Electrical substitution is direct. Pin configuration and signal timing are identical. PCB layout modification is required due to different package footprints (28-TSSOP versus 28-SOIC).

Q: What is the primary reason for substitution?

A: The AT28HC256F-90TU is classified as obsolete. The AT28HC256F-90SU maintains active product status with ongoing manufacturing availability.

Q: Are there compliance differences between these parts?

A: Both parts are ROHS3 compliant and REACH unaffected. The AT28HC256F-90SU has a lower moisture sensitivity level (MSL 2 versus MSL 3), providing improved handling and storage characteristics.

Q: What are the package dimension differences?

A: AT28HC256F-90TU uses 28-TSSOP (0.465" width, 11.80mm). AT28HC256F-90SU uses 28-SOIC (0.295" width, 7.50mm). Both are surface mount packages with 28-pin configurations.

Q: Are memory specifications identical?

A: Yes. Both devices provide 256Kbit capacity in 32K x 8 organization with 90 ns access time, 3 ms write cycle time, and 4.5V to 5.5V supply voltage operation.

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