FM93CS46M8 EEPROM 1Kbit Microwire Equivalent & Substitute Parts

Part Overview

The FM93CS46M8 is a 1Kbit non-volatile EEPROM memory IC manufactured by onsemi, featuring Microwire serial interface protocol and 8-SOIC surface mount packaging. This component is classified as obsolete, indicating discontinued production and limited availability in the market. The identification of equivalent substitute parts is necessary to maintain design continuity and ensure component procurement for new production runs or legacy system maintenance.

Key Parameters

Parameter	Value
Manufacturer Part Number	FM93CS46M8
Manufacturer	onsemi
Memory Type	Non-Volatile EEPROM
Memory Size	1Kbit
Memory Organization	64 x 16
Memory Interface	Microwire
Clock Frequency	1 MHz
Write Cycle Time	10ms
Supply Voltage	4.5V ~ 5.5V
Operating Temperature	0°C ~ 70°C
Package / Case	8-SOIC (0.154", 3.90mm Width)
Mounting Type	Surface Mount
Product Status	Obsolete
RoHS Status	RoHS non-compliant

Substitute Part Grouping Explanation

Substitute parts for the FM93CS46M8 are identified based on the following critical parameters that determine functional compatibility:

Memory Capacity & Organization: All substitute parts maintain 1Kbit capacity with 64 x 16 organization, ensuring identical data storage capability.

Physical Package: All substitutes use 8-SOIC (0.154", 3.90mm Width) surface mount packaging, providing direct PCB footprint compatibility.

Non-Volatile EEPROM Technology: All substitutes employ EEPROM technology for non-volatile data retention.

Serial Interface Protocol: The FM93CS46M8 uses Microwire protocol. Substitute parts identified (M93S46-WMN6P and M93S46-WMN6TP) implement SPI protocol, which represents a protocol change requiring design verification.

Electrical Compatibility: Substitute parts support extended supply voltage range (2.5V ~ 5.5V) compared to the original (4.5V ~ 5.5V), providing broader operational flexibility.

Temperature Range: Substitute parts operate across -40°C ~ 85°C, exceeding the original 0°C ~ 70°C range.

Parameter Comparison

Parameter	FM93CS46M8 (onsemi)	M93S46-WMN6P (STMicroelectronics)	M93S46-WMN6TP (STMicroelectronics)
Memory Size	1Kbit	1Kbit	1Kbit
Memory Organization	64 x 16	64 x 16	64 x 16
Memory Interface	Microwire	SPI	SPI
Clock Frequency	1 MHz	2 MHz	2 MHz
Write Cycle Time	10ms	5ms	5ms
Supply Voltage	4.5V ~ 5.5V	2.5V ~ 5.5V	2.5V ~ 5.5V
Operating Temperature	0°C ~ 70°C	-40°C ~ 85°C	-40°C ~ 85°C
Package / Case	8-SOIC (0.154", 3.90mm Width)	8-SOIC (0.154", 3.90mm Width)	8-SOIC (0.154", 3.90mm Width)
Product Status	Obsolete	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant
Packaging Option	Not specified	Tube	Cut Tape (CT) & Digi-Reel®

Engineering Selection Recommendations

The M93S46-WMN6P and M93S46-WMN6TP are active production parts from STMicroelectronics, providing long-term availability and supply chain stability compared to the obsolete FM93CS46M8.

Both substitute parts achieve ROHS3 compliance, meeting current environmental and regulatory requirements. The FM93CS46M8 is RoHS non-compliant, which may restrict use in applications subject to RoHS directives.

The substitutes offer improved electrical performance with faster write cycle times (5ms versus 10ms) and higher maximum clock frequency (2 MHz versus 1 MHz). Extended operating temperature range (-40°C ~ 85°C) and broader supply voltage tolerance (2.5V ~ 5.5V) provide enhanced operational flexibility.

The primary design consideration is the serial interface protocol change from Microwire to SPI. This requires firmware or controller modification to accommodate the different communication protocol, as Microwire and SPI are not directly interchangeable at the software level.

M93S46-WMN6TP in Cut Tape & Digi-Reel® packaging offers flexibility for both prototype and production quantities. M93S46-WMN6P in Tube packaging is suitable for standard production volumes.

Frequently Asked Questions (FAQ)

Q: Can M93S46-WMN6P or M93S46-WMN6TP be used as direct drop-in replacements for FM93CS46M8?

A: Physical package compatibility is confirmed (8-SOIC footprint). However, the serial interface protocol differs: FM93CS46M8 uses Microwire while the substitutes use SPI. This requires controller firmware modification to support the different communication protocol. Direct PCB substitution without firmware changes will not function.

Q: What are the key differences between M93S46-WMN6P and M93S46-WMN6TP?

A: Both parts are electrically identical with identical specifications. The difference is packaging format: M93S46-WMN6P is supplied in Tube packaging, while M93S46-WMN6TP is supplied in Cut Tape (CT) & Digi-Reel® format. Selection depends on procurement quantity and handling requirements.

Q: Are the substitute parts compatible with the original 4.5V ~ 5.5V supply voltage range?

A: Yes. The substitute parts support 2.5V ~ 5.5V supply voltage, which encompasses the original 4.5V ~ 5.5V range. Designs operating at 4.5V ~ 5.5V will function with the substitutes without voltage modification.

Q: What is the impact of the faster write cycle time (5ms vs 10ms) on system design?

A: The faster write cycle time of the substitute parts (5ms) is an improvement over the original (10ms). This reduces data write latency and may improve overall system performance. No design modifications are required; the faster performance is transparent to the application.

Q: Do the substitute parts meet current regulatory compliance requirements?

A: Yes. Both M93S46-WMN6P and M93S46-WMN6TP are ROHS3 compliant and REACH unaffected, meeting current environmental and regulatory standards. The original FM93CS46M8 is RoHS non-compliant, which may restrict its use in regulated applications.

Q: What is the inventory status of these parts?

A: FM93CS46M8 (obsolete): 3000 Pcs in stock. M93S46-WMN6P (active): 6570 Pcs in stock. M93S46-WMN6TP (active): 3439 Pcs in stock. Active production parts provide superior long-term availability.

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