FM93CS66N EEPROM 4Kbit Microwire Equivalent & Substitute Parts

Part Overview

The FM93CS66N is a 4Kbit EEPROM memory IC with Microwire interface manufactured by onsemi. This device is classified as obsolete, which necessitates identification of functionally equivalent alternatives for ongoing system support and new designs. The FM93CS66N operates at 1 MHz clock frequency with a 10ms write cycle time and is designed for through-hole mounting in 8-DIP packaging. Equivalent parts must maintain compatibility with the 256 x 16 memory organization, Microwire serial interface, and 4.5V to 5.5V supply voltage specifications.

Substiute Parts

FM93CS66N

onsemiIn Stock: 869FM93CS66N Datasheet

Current PartRFQ

93C66B-E/P

Microchip TechnologyIn Stock: 70193C66B-E/P Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution of the FM93CS66N is based on the following critical parameters that must remain constant or be compatible:

• Memory capacity and organization (4Kbit, 256 x 16)
• Serial interface protocol (Microwire)
• Supply voltage range (4.5V ~ 5.5V)
• Package form factor (8-DIP through-hole)
• Pin configuration compatibility

The 93C66B-E/P manufactured by Microchip Technology satisfies these core requirements. While this substitute operates at 2 MHz clock frequency and features a 2ms write cycle time (both superior to the original), it maintains full electrical and mechanical compatibility with the FM93CS66N. The enhanced performance characteristics do not create substitution conflicts, as faster operation is backward-compatible with systems designed for the original 1 MHz device.

Parameter Comparison

Engineering Selection Recommendations

The 93C66B-E/P is the qualified substitute for the FM93CS66N based on the following factors:

• Maintains identical memory capacity, organization, and Microwire interface protocol
• Operates within the same supply voltage range (4.5V ~ 5.5V)
• Shares compatible 8-DIP through-hole package footprint
• Offers active product status, ensuring long-term availability and supply chain continuity
• Achieves ROHS3 compliance, meeting current environmental and regulatory standards
• Provides enhanced performance specifications (2 MHz operation, 2ms write cycle) that are fully backward-compatible with original design parameters

The extended operating temperature range (-40°C ~ 125°C) of the 93C66B-E/P accommodates broader environmental conditions compared to the original device (0°C ~ 70°C), presenting no substitution limitations.

Frequently Asked Questions (FAQ)

Q: Can the 93C66B-E/P directly replace the FM93CS66N without circuit modifications?

A: Yes. The 93C66B-E/P maintains electrical and mechanical compatibility with the FM93CS66N. Both devices share identical memory organization, Microwire interface protocol, supply voltage range, and 8-DIP package footprint. No circuit modifications are required for direct substitution.

Q: What is the significance of the higher clock frequency (2 MHz vs. 1 MHz) in the substitute part?

A: The 93C66B-E/P operates at 2 MHz, which is faster than the original 1 MHz specification. This enhanced performance is fully backward-compatible with systems designed for the FM93CS66N. The faster clock frequency does not create compatibility issues; it only improves data transfer speed.

Q: Does the improved write cycle time (2ms vs. 10ms) affect system compatibility?

A: No. The reduced write cycle time of the 93C66B-E/P is a performance enhancement that does not compromise compatibility. Systems designed for the 10ms write cycle of the FM93CS66N will function correctly with the faster 2ms write cycle of the substitute.

Q: Are there package differences between the FM93CS66N and 93C66B-E/P?

A: Both devices use 8-DIP through-hole packages with identical 0.300" (7.62mm) spacing. The packages are mechanically and electrically compatible for PCB mounting and circuit integration.

Q: Why is RoHS compliance important for this substitution?

A: The 93C66B-E/P achieves ROHS3 compliance, while the FM93CS66N is non-compliant. For new designs and systems subject to environmental regulations, the compliant substitute ensures adherence to current standards and supports long-term product certification requirements.

Q: What is the temperature operating range difference, and does it matter?

A: The FM93CS66N operates from 0°C to 70°C, while the 93C66B-E/P operates from -40°C to 125°C. The wider temperature range of the substitute provides greater flexibility for applications requiring extended environmental conditions. This difference does not prevent substitution in standard operating environments.