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AT28HC256-70SC EEPROM Memory IC Equivalent & Substitute Parts
Part Overview
The AT28HC256-70SC is a 256Kbit parallel EEPROM memory IC manufactured by Microchip Technology, housed in a 28-SOIC surface mount package with 70 ns access time. This device is classified as obsolete, making identification of compatible substitute parts essential for ongoing system support and component procurement. The part operates within a 4.5V to 5.5V supply voltage range and supports 32K x 8 memory organization with 10ms write cycle time.
Substiute Parts
Key Parameters
| Parameter | Value |
|---|---|
| Memory Size | 256Kbit |
| Memory Organization | 32K x 8 |
| Memory Interface | Parallel |
| Access Time | 70 ns |
| Write Cycle Time | 10ms |
| Voltage Supply Range | 4.5V ~ 5.5V |
| Package Type | 28-SOIC (0.295", 7.50mm Width) |
| Mounting Type | Surface Mount |
Substitute Part Grouping Explanation
Substitution of the AT28HC256-70SC is determined by strict equivalence across the following parameters:
- Memory capacity and organization (256Kbit, 32K x 8)
- Memory interface type (Parallel)
- Access time specification (70 ns)
- Write cycle time (10ms)
- Supply voltage range (4.5V ~ 5.5V)
- Package and pinout (28-SOIC)
- Mounting technology (Surface Mount)
The AT28HC256-70SU meets all these criteria and is therefore a direct functional equivalent. The primary distinction between these parts lies in product status, operating temperature range, packaging format, and compliance certifications rather than electrical or mechanical specifications.
Parameter Comparison
| Parameter | AT28HC256-70SC | AT28HC256-70SU | Compatibility |
|---|---|---|---|
| Memory Size | 256Kbit | 256Kbit | Identical |
| Memory Organization | 32K x 8 | 32K x 8 | Identical |
| Memory Interface | Parallel | Parallel | Identical |
| Access Time | 70 ns | 70 ns | Identical |
| Write Cycle Time | 10ms | 10ms | Identical |
| Voltage Supply | 4.5V ~ 5.5V | 4.5V ~ 5.5V | Identical |
| Package / Case | 28-SOIC (0.295", 7.50mm Width) | 28-SOIC (0.295", 7.50mm Width) | Identical |
| Mounting Type | Surface Mount | Surface Mount | Identical |
| Operating Temperature | 0°C ~ 70°C | -40°C ~ 85°C | AT28HC256-70SU has extended range |
| Product Status | Obsolete | Active | AT28HC256-70SU actively manufactured |
| RoHS Status | RoHS non-compliant | ROHS3 Compliant | AT28HC256-70SU meets current standards |
| Packaging Format | Tape and Reel | Tube | Different packaging options |
Engineering Selection Recommendations
The AT28HC256-70SU is the direct substitute for the AT28HC256-70SC based on identical electrical and mechanical specifications. Selection of the AT28HC256-70SU is supported by the following factors:
- Active product status ensures ongoing availability and manufacturing support
- ROHS3 compliance aligns with current regulatory requirements
- Extended operating temperature range (-40°C ~ 85°C) provides broader environmental compatibility compared to the original part (0°C ~ 70°C)
- Identical core memory specifications guarantee functional equivalence in parallel EEPROM applications
- Tube packaging format offers alternative procurement and handling options
For applications requiring the original operating temperature specification (0°C ~ 70°C), the AT28HC256-70SU remains compatible as it exceeds the minimum temperature range requirement.
Frequently Asked Questions (FAQ)
Q: Can the AT28HC256-70SU directly replace the AT28HC256-70SC in existing designs?
A: Yes. Both parts share identical memory capacity (256Kbit), organization (32K x 8), parallel interface, access time (70 ns), write cycle time (10ms), supply voltage (4.5V ~ 5.5V), and 28-SOIC package specifications. Pin-for-pin compatibility is maintained.
Q: What is the significance of the different operating temperature ranges?
A: The AT28HC256-70SC operates from 0°C to 70°C, while the AT28HC256-70SU operates from -40°C to 85°C. The AT28HC256-70SU's extended range encompasses the original specification, making it suitable for applications across both temperature ranges.
Q: Why is the AT28HC256-70SC classified as obsolete?
A: Obsolete status indicates the part is no longer in active production. The AT28HC256-70SU, as an active product from the same manufacturer with identical electrical specifications, serves as the current production equivalent.
Q: Are there packaging differences between these parts?
A: Yes. The AT28HC256-70SC is supplied in tape and reel format, while the AT28HC256-70SU is supplied in tube packaging. Both use the same 28-SOIC package type and dimensions.
Q: Does the RoHS compliance difference affect substitution?
A: The AT28HC256-70SU is ROHS3 compliant, while the AT28HC256-70SC is non-compliant. For new designs or systems requiring RoHS compliance, the AT28HC256-70SU is the appropriate selection. For legacy system maintenance, both parts are electrically equivalent.
Q: Are there any restrictions on using the AT28HC256-70SU in place of the AT28HC256-70SC?
A: No electrical or mechanical restrictions exist. The substitute part meets or exceeds all specified parameters of the original part.
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