Equivalent & Substitute Parts for 23A640-I/ST

Part Overview

The 23A640-I/ST is a 64Kbit SRAM memory IC manufactured by Microchip Technology, featuring SPI interface operation at 20 MHz. This volatile memory device is housed in an 8-TSSOP surface mount package and operates across the temperature range of -40°C to 85°C with a supply voltage of 1.7V to 1.95V. The part maintains Active product status with full RoHS3 compliance and unlimited moisture sensitivity rating (MSL 1). Substitute parts become relevant when addressing inventory constraints, supply chain disruptions, or when legacy components require replacement in production environments.

Key Parameters

Parameter	Value
Memory Type	Volatile SRAM
Memory Size	64Kbit
Memory Organization	8K x 8
Memory Interface	SPI
Clock Frequency	20 MHz
Voltage Supply Range	1.7V ~ 1.95V
Operating Temperature	-40°C ~ 85°C
Package Type	8-TSSOP (0.173", 4.40mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution eligibility for the 23A640-I/ST is determined by strict alignment across the following critical parameters:

Memory Capacity & Organization: 64Kbit capacity with 8K x 8 organization
Interface Protocol: SPI serial interface requirement
Package Compatibility: 8-TSSOP surface mount package with identical 0.173" width and 4.40mm dimensions
Electrical Specifications: Supply voltage range 1.7V ~ 1.95V and operating temperature range -40°C ~ 85°C
Compliance Standards: RoHS3 compliance and REACH unaffected status

The N64S818HAT21I from onsemi meets all mandatory substitution criteria across memory capacity, organization, interface type, and package specifications. Clock frequency variance (16 MHz versus 20 MHz) represents a functional difference that must be evaluated within specific application timing requirements.

Parameter Comparison

Parameter	23A640-I/ST (Microchip)	N64S818HAT21I (onsemi)	Compatibility Status
Memory Type	Volatile SRAM	Volatile SRAM	Match
Memory Size	64Kbit	64Kbit	Match
Memory Organization	8K x 8	8K x 8	Match
Memory Interface	SPI	SPI	Match
Clock Frequency	20 MHz	16 MHz	Variance
Voltage Supply Range	1.7V ~ 1.95V	1.7V ~ 1.95V	Match
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	Match
Package Type	8-TSSOP (0.173", 4.40mm)	8-TSSOP (0.173", 4.40mm)	Match
Mounting Type	Surface Mount	Surface Mount	Match
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Match
REACH Status	REACH Unaffected	REACH Unaffected	Match
Product Status	Active	Obsolete	Variance
MSL Rating	1 (Unlimited)	3 (168 Hours)	Variance

Engineering Selection Recommendations

The N64S818HAT21I qualifies as a functional substitute based on matching memory capacity, organization, SPI interface, package geometry, electrical specifications, and regulatory compliance. However, three factors require evaluation:

Clock Frequency: The substitute operates at 16 MHz versus the primary part's 20 MHz. Applications with timing-critical SPI communication protocols must confirm that 16 MHz operation satisfies system requirements.

Product Status: The primary part maintains Active status while the substitute is classified as Obsolete. Long-term supply availability for the N64S818HAT21I may be limited, making it suitable for near-term replacement scenarios rather than new design implementations.

Moisture Sensitivity: The primary part carries MSL 1 (unlimited shelf life), while the substitute carries MSL 3 (168-hour maximum floor life after moisture exposure). Storage and handling procedures must account for the reduced moisture tolerance window of the substitute.

Frequently Asked Questions (FAQ)

Q: Can the N64S818HAT21I directly replace the 23A640-I/ST in existing designs?

A: Direct replacement is possible from a package and electrical standpoint. The 8-TSSOP footprint is identical, supply voltage ranges match, and operating temperature specifications align. However, the 16 MHz clock frequency of the substitute versus the 20 MHz of the primary part must be validated against application timing requirements before implementation.

Q: What is the significance of the Obsolete product status for the N64S818HAT21I?

A: Obsolete status indicates that onsemi has discontinued active production and support for this part number. While current inventory may be available through distributors, future procurement cannot be guaranteed. This substitute is appropriate for addressing immediate supply needs but should not be selected for new product designs requiring long-term component availability.

Q: How does the MSL 3 rating of the substitute affect handling procedures?

A: MSL 3 specifies a maximum floor life of 168 hours after the component is exposed to moisture. The primary part's MSL 1 rating allows unlimited shelf life. Organizations using the substitute must implement moisture control measures during storage and establish strict handling timelines post-exposure to prevent moisture-related failures during assembly.

Q: Are both parts suitable for the same operating temperature range?

A: Yes. Both the 23A640-I/ST and N64S818HAT21I operate across -40°C to 85°C, ensuring thermal compatibility across standard industrial and commercial temperature specifications.

Q: What compliance certifications apply to both parts?

A: Both parts maintain ROHS3 compliance and REACH unaffected status, satisfying environmental and hazardous substance regulations for EU and global markets.

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