CD74HC688PWT Equivalent & Substitute Parts

Part Overview

The CD74HC688PWT is an 8-bit magnitude comparator identity IC manufactured by Texas Instruments, designed for logic-level comparison applications. This device features active-low output with A=B function, operating across a 2V to 6V supply voltage range. The part is currently discontinued at DiGi Electronics, making equivalent substitutes necessary for ongoing production and maintenance applications. Substitute parts maintain identical functional specifications and packaging while offering continued availability through active product lines.

Key Parameters

Parameter	Value
Part Number	CD74HC688PWT
Manufacturer	Texas Instruments
Category	Logic - Identity Comparator
Number of Bits	8
Output Type	Active Low (A=B)
Voltage Supply Range	2V ~ 6V
Output Current (High/Low)	5.2mA / 5.2mA
Max Propagation Delay	29ns @ 6V, 50pF
Quiescent Current	8 µA
Operating Temperature	-55°C ~ 125°C
Package	20-TSSOP (0.173", 4.40mm Width)
Mounting Type	Surface Mount
RoHS Status	ROHS3 Compliant
MSL Rating	1 (Unlimited)

Substitute Part Grouping Explanation

Substitute parts for the CD74HC688PWT are qualified based on the following critical parameters:

Functional Equivalence: 8-bit magnitude comparator with active-low A=B output function
Electrical Compatibility: Supply voltage range 2V ~ 6V, output current 5.2mA, propagation delay 29ns @ 6V with 50pF load
Package Compatibility: 20-TSSOP surface mount package with identical pinout and mechanical dimensions
Thermal Range: Operating temperature -55°C ~ 125°C (or compatible subset)
Compliance: ROHS3 compliant, MSL 1 rating, REACH unaffected status

Two direct substitutes meet these criteria: CD74HC688PWR (Texas Instruments, active product status) and 74HC688PW,118 (Nexperia USA Inc., manufacturer-recommended alternative). Both maintain identical electrical specifications and package configuration, enabling direct board-level replacement without design modification.

Parameter Comparison

Parameter	CD74HC688PWT (Main)	CD74HC688PWR (Substitute)	74HC688PW,118 (Substitute)
Manufacturer	Texas Instruments	Texas Instruments	Nexperia USA Inc.
Product Status	Discontinued	Active	Active
Number of Bits	8	8	8
Output Function	A=B (Active Low)	A=B (Active Low)	A=B (Active Low)
Voltage Supply	2V ~ 6V	2V ~ 6V	2V ~ 6V
Output Current (High/Low)	5.2mA / 5.2mA	5.2mA / 5.2mA	5.2mA / 5.2mA
Max Propagation Delay	29ns @ 6V, 50pF	29ns @ 6V, 50pF	29ns @ 6V, 50pF
Quiescent Current	8 µA	8 µA	8 µA
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-40°C ~ 125°C
Package	20-TSSOP	20-TSSOP	20-TSSOP
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
MSL Rating	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

CD74HC688PWR is the primary substitute, maintaining identical specifications across all electrical and thermal parameters while offering active product status from the original manufacturer. This part provides continuity with the discontinued CD74HC688PWT without design modification.

74HC688PW,118 from Nexperia USA Inc. is a manufacturer-recommended alternative with equivalent electrical performance and identical packaging. The operating temperature range extends to -40°C minimum (versus -55°C for the original), which is acceptable for applications not requiring the extended low-temperature specification. This part is actively produced and widely available.

Both substitutes are ROHS3 compliant with MSL 1 ratings, ensuring compatibility with standard manufacturing and storage protocols. Selection between CD74HC688PWR and 74HC688PW,118 depends on supply chain availability and thermal requirement verification for specific applications.

Frequently Asked Questions (FAQ)

Q: Can CD74HC688PWR be used as a direct replacement for CD74HC688PWT?

A: Yes. CD74HC688PWR is electrically and mechanically identical to CD74HC688PWT, with all critical parameters matching exactly. The only difference is product status (active versus discontinued). Direct board-level substitution is possible without design changes.

Q: What is the difference between CD74HC688PWR and 74HC688PW,118?

A: Both parts are 8-bit magnitude comparators with identical electrical specifications and 20-TSSOP packaging. The primary difference is manufacturer: CD74HC688PWR is from Texas Instruments, while 74HC688PW,118 is from Nexperia USA Inc. The operating temperature minimum for 74HC688PW,118 is -40°C instead of -55°C. Both are ROHS3 compliant and actively produced.

Q: Are these parts pin-compatible?

A: Yes. All three parts (CD74HC688PWT, CD74HC688PWR, and 74HC688PW,118) use the 20-TSSOP package with identical pinout and mechanical dimensions. No PCB layout modifications are required for substitution.

Q: What does "Active Low" output mean for the A=B function?

A: The A=B output is asserted (logic low) when the 8-bit input A equals the 8-bit input B. When A does not equal B, the output is deasserted (logic high). This is standard for identity comparators in the 74HC series.

Q: Can I use 74HCT04D,653 as a substitute?

A: No. The 74HCT04D,653 is a 6-channel inverter IC with different functional purpose, electrical specifications, and package configuration. It is not equivalent to the CD74HC688PWT magnitude comparator and cannot be substituted.

Q: What is the significance of the 20-TSSOP package specification?

A: The 20-TSSOP (Thin Shrink Small Outline Package) is a surface-mount package with 20 pins, 0.173 inches wide, and 4.40mm body width. All qualified substitutes use this identical package, ensuring mechanical and electrical compatibility on PCBs designed for the original part.

Q: Are there any compliance or certification differences between the substitutes?

A: No. All three parts (CD74HC688PWT, CD74HC688PWR, and 74HC688PW,118) carry identical ROHS3 compliance, MSL 1 ratings, REACH unaffected status, and ECCN/HTSUS classifications. Compliance documentation is equivalent across all substitutes.

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