IS62C256-70UI Equivalent & Substitute Parts

Part Overview

The IS62C256-70UI is a 256Kbit asynchronous SRAM memory IC manufactured by ISSI (Integrated Silicon Solution Inc). This parallel interface memory device operates with a 70 ns access time and write cycle time, housed in a 28-SOP package. The part is classified as obsolete, making identification of compatible substitute components essential for ongoing system support and new design implementations. Active production alternatives with improved performance characteristics are available to maintain design continuity.

Key Parameters

Parameter	Value
Memory Size	256Kbit
Memory Organization	32K x 8
Memory Format	SRAM
Memory Interface	Parallel
Access Time	70 ns
Write Cycle Time	70 ns
Voltage Supply Range	4.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C
Package Type	28-SOP
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant
MSL Rating	3 (168 Hours)

Substitute Part Grouping Explanation

Substitution of the IS62C256-70UI is determined by strict equivalence in the following critical parameters:

Memory capacity and organization (256Kbit, 32K x 8 configuration) must remain identical to ensure functional compatibility. The parallel interface requirement is non-negotiable for pin-level compatibility. Package type (28-SOP) and mounting method (surface mount) must match to maintain PCB layout compatibility.

Voltage supply range (4.5V ~ 5.5V) and operating temperature range (-40°C ~ 85°C) establish the environmental operating envelope. RoHS3 compliance and MSL rating (3, 168 Hours) are mandatory for manufacturing and reliability standards.

The IS62C256AL-45ULI qualifies as a direct substitute because it maintains identical memory capacity, organization, interface type, package, mounting method, voltage range, temperature range, and compliance certifications. The improved access time (45 ns versus 70 ns) and write cycle time (45 ns versus 70 ns) represent performance enhancement without functional incompatibility, as faster memory is backward-compatible with systems designed for slower access times.

Parameter Comparison

Parameter	IS62C256-70UI (Main Part)	IS62C256AL-45ULI (Substitute)
Memory Size	256Kbit	256Kbit
Memory Organization	32K x 8	32K x 8
Memory Format	SRAM	SRAM
Memory Interface	Parallel	Parallel
Access Time	70 ns	45 ns
Write Cycle Time	70 ns	45 ns
Voltage Supply Range	4.5V ~ 5.5V	4.5V ~ 5.5V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C
Package Type	28-SOP	28-SOIC (0.330", 8.38mm Width)
Mounting Type	Surface Mount	Surface Mount
RoHS Status	ROHS3 Compliant	ROHS3 Compliant
MSL Rating	3 (168 Hours)	3 (168 Hours)
Product Status	Obsolete	Active

Engineering Selection Recommendations

The IS62C256AL-45ULI is the designated manufacturer-recommended substitute for the obsolete IS62C256-70UI. Both components maintain identical electrical specifications for memory capacity, organization, interface protocol, voltage supply range, and operating temperature range. Both achieve ROHS3 compliance and carry equivalent MSL ratings.

The substitute part offers improved performance through reduced access time and write cycle time (45 ns versus 70 ns), which provides timing margin enhancement without introducing incompatibility. The substitute maintains active production status, ensuring long-term availability and supply chain stability compared to the obsolete main part.

Surface mount packaging and 28-pin SOP configuration remain consistent between both parts, supporting direct PCB layout compatibility. The substitute part is available in significantly higher inventory quantities (35,300 pcs versus 1,154 pcs), supporting both immediate procurement needs and future production requirements.

Frequently Asked Questions (FAQ)

Q: Can the IS62C256AL-45ULI directly replace the IS62C256-70UI in existing designs?

A: Yes. Both parts maintain identical memory capacity (256Kbit), organization (32K x 8), parallel interface, 28-SOP package configuration, voltage supply range (4.5V ~ 5.5V), and operating temperature range (-40°C ~ 85°C). The improved access time of the substitute part does not create functional incompatibility.

Q: What is the primary difference between these two parts?

A: The IS62C256AL-45ULI provides faster memory access and write cycle times (45 ns) compared to the IS62C256-70UI (70 ns). The substitute part is in active production, whereas the main part is obsolete.

Q: Are there any package compatibility concerns?

A: Both parts use 28-pin SOP surface mount packages. The substitute specifies 28-SOIC (0.330", 8.38mm Width) while the main part uses 28-SOP. These package designations refer to the same physical form factor and are compatible for PCB assembly.

Q: Do both parts meet current compliance requirements?

A: Yes. Both the IS62C256-70UI and IS62C256AL-45ULI are ROHS3 compliant and carry MSL rating 3 (168 Hours), meeting current manufacturing and environmental standards.

Q: Why should I transition from the obsolete part to the substitute?

A: The main part is classified as obsolete, creating long-term supply risk. The substitute is in active production with higher inventory availability, ensuring reliable procurement for current and future applications.

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