SN74HC688DW Equivalent & Substitute Parts

Part Overview

The SN74HC688DW is an 8-bit identity comparator manufactured by Texas Instruments, designed for magnitude comparison applications with active low output. This device is currently discontinued at DiGi Electronics, making equivalent and substitute parts necessary for ongoing production and maintenance applications. The part operates across a 2V to 6V supply range and is housed in a 20-SOIC surface mount package.

Key Parameters

Parameter	Value
Part Number	SN74HC688DW
Manufacturer	Texas Instruments
Category	Logic - Identity Comparator
Number of Bits	8
Output Type	Active Low (A=B)
Voltage Supply Range	2V ~ 6V
Package / Case	20-SOIC (0.295", 7.50mm Width)
Mounting Type	Surface Mount
Operating Temperature	-40°C ~ 85°C
Product Status	Discontinued at DiGi Electronics
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution for the SN74HC688DW is determined by the following critical parameters:

Functional Type: Identity Comparator with 8-bit comparison capability
Output Configuration: Active Low output with A=B function
Voltage Supply Range: 2V ~ 6V operating range
Package Format: 20-SOIC surface mount package
Bit Width: 8-bit comparison
Compliance: ROHS3 compliant, RoHS and REACH status

The SN74HC688DWR qualifies as a direct equivalent, maintaining identical electrical and mechanical specifications while offering active product status. The 74HC688D,653 from Nexperia USA Inc. provides functional equivalence with improved propagation delay performance and extended operating temperature range, though it uses a 20-SO package designation. The 74HCT02D,653 does not qualify as a functional substitute due to different logic type (NOR Gate vs. Identity Comparator) and incompatible supply voltage range (4.5V ~ 5.5V vs. 2V ~ 6V).

Parameter Comparison

Parameter	SN74HC688DW	SN74HC688DWR	74HC688D,653
Manufacturer	Texas Instruments	Texas Instruments	Nexperia USA Inc.
Series	74HC	74HC	74HC
Type	Identity Comparator	Identity Comparator	Identity Comparator
Number of Bits	8	8	8
Output	Active Low	Active Low	Active Low
Output Function	A=B	A=B	A=B
Voltage - Supply	2V ~ 6V	2V ~ 6V	2V ~ 6V
Current - Output High, Low	5.2mA, 5.2mA	5.2mA, 5.2mA	5.2mA, 5.2mA
Max Propagation Delay @ V, Max CL	36ns @ 6V, 50pF	36ns @ 6V, 50pF	29ns @ 6V, 50pF
Current - Quiescent (Iq)	8 µA	8 µA	8 µA
Operating Temperature	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 125°C
Package / Case	20-SOIC (0.295", 7.50mm Width)	20-SOIC (0.295", 7.50mm Width)	20-SOIC (0.295", 7.50mm Width)
Mounting Type	Surface Mount	Surface Mount	Surface Mount
Product Status	Discontinued at DiGi Electronics	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For applications requiring the SN74HC688DW, the SN74HC688DWR is the primary substitute. Both parts are manufactured by Texas Instruments, maintain identical electrical specifications, and share the same package format. The SN74HC688DWR offers the advantage of active product status with equivalent inventory availability.

The 74HC688D,653 from Nexperia USA Inc. serves as an alternative substitute with improved propagation delay performance (29ns versus 36ns) and extended operating temperature range (-40°C to 125°C versus -40°C to 85°C). This part maintains functional equivalence and ROHS3 compliance. The package designation difference (20-SO versus 20-SOIC) does not affect mechanical compatibility for standard surface mount assembly processes.

The 74HCT02D,653 is not suitable as a substitute due to fundamental functional incompatibility. This part is a NOR gate logic device rather than an identity comparator, operates on a different supply voltage range (4.5V ~ 5.5V), and cannot perform the required 8-bit comparison function.

Frequently Asked Questions (FAQ)

Q: Can the SN74HC688DWR be used as a direct replacement for the SN74HC688DW?

A: Yes. The SN74HC688DWR is a direct equivalent with identical electrical characteristics, package format, and functional specifications. The primary difference is product status; the DWR variant is currently active in production.

Q: What are the advantages of using the 74HC688D,653 as a substitute?

A: The 74HC688D,653 provides faster propagation delay (29ns versus 36ns at 6V, 50pF) and an extended operating temperature range (-40°C to 125°C versus -40°C to 85°C). Both parts maintain the same 8-bit identity comparator function and 2V ~ 6V supply range.

Q: Are there package compatibility concerns between the 20-SOIC and 20-SO designations?

A: No. Both designations refer to 20-pin small outline packages with identical physical dimensions (0.295" width, 7.50mm). Standard surface mount assembly equipment handles both package types identically.

Q: Why is the 74HCT02D,653 not a suitable substitute?

A: The 74HCT02D,653 is a NOR gate logic device, not an identity comparator. It cannot perform 8-bit magnitude comparison and operates on a different supply voltage range (4.5V ~ 5.5V versus 2V ~ 6V). Functional incompatibility makes this part unsuitable for applications requiring the SN74HC688DW.

Q: What compliance certifications apply to all substitute parts?

A: All substitute parts listed maintain ROHS3 compliance, REACH unaffected status, and EAR99 export classification. Moisture sensitivity level is 1 (Unlimited) for all variants.

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