74LCX821WMX Equivalent & Substitute Parts

Part Overview

The 74LCX821WMX is a single-element D-type flip-flop logic integrated circuit with 10-bit capacity, manufactured by onsemi in a 24-SOIC surface mount package. This device is classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing system support and new design implementations. The 74LCX series operates across a 2V to 3.6V supply range with positive edge triggering and tri-state non-inverted outputs, serving as a standard logic component in digital circuit applications.

Key Parameters

Parameter	Value
Manufacturer Part Number	74LCX821WMX
Manufacturer	onsemi
Category	Logic
Type	D-Type Flip Flop
Number of Elements	1
Number of Bits per Element	10
Package / Case	24-SOIC (0.295", 7.50mm Width)
Clock Frequency	150 MHz
Voltage - Supply	2V ~ 3.6V
Operating Temperature	-40°C ~ 85°C (TA)
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution of the 74LCX821WMX is determined by the following critical parameters:

Package Compatibility: Both substitute parts maintain the 24-SOIC (0.295", 7.50mm Width) surface mount package, ensuring mechanical and electrical pin compatibility.
Functional Equivalence: All parts are single-element D-type flip-flops with 10-bit capacity, positive edge triggering, and tri-state non-inverted outputs.
Electrical Performance: Clock frequency (150 MHz), output current ratings (24mA high/low), quiescent current (10 µA), and operating temperature range (-40°C ~ 85°C) are identical across all parts.
Supply Voltage Range: The 74LCX821WMX operates at 2V ~ 3.6V. Substitute parts from the 74LVC series operate at 1.65V ~ 3.6V, providing extended lower voltage capability while maintaining full compatibility within the original operating range.
Series Transition: The 74LVC series represents the active production equivalent to the obsolete 74LCX series, with improved specifications and current manufacturing support.

Parameter Comparison

Parameter	74LCX821WMX (onsemi)	SN74LVC821ADW (TI)	SN74LVC821ADWR (TI)
Manufacturer	onsemi	Texas Instruments	Texas Instruments
Product Status	Obsolete	Active	Active
Type	D-Type Flip Flop	D-Type Flip Flop	D-Type Flip Flop
Number of Elements	1	1	1
Number of Bits per Element	10	10	10
Package / Case	24-SOIC (0.295", 7.50mm Width)	24-SOIC (0.295", 7.50mm Width)	24-SOIC (0.295", 7.50mm Width)
Clock Frequency	150 MHz	150 MHz	150 MHz
Max Propagation Delay @ 3.3V, 50pF	7ns	7.3ns	7.3ns
Current - Output High, Low	24mA, 24mA	24mA, 24mA	24mA, 24mA
Voltage - Supply	2V ~ 3.6V	1.65V ~ 3.6V	1.65V ~ 3.6V
Current - Quiescent (Iq)	10 µA	10 µA	10 µA
Input Capacitance	7 pF	5 pF	5 pF
Operating Temperature	-40°C ~ 85°C (TA)	-40°C ~ 85°C (TA)	-40°C ~ 85°C (TA)
Mounting Type	Surface Mount	Surface Mount	Surface Mount
Output Type	Tri-State, Non-Inverted	Tri-State, Non-Inverted	Tri-State, Non-Inverted
Trigger Type	Positive Edge	Positive Edge	Positive Edge
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant
Packaging Format	Not specified	Tube	Tape & Reel (TR)

Engineering Selection Recommendations

Both SN74LVC821ADW and SN74LVC821ADWR are direct functional substitutes for the obsolete 74LCX821WMX. Selection between these alternatives is based on procurement and assembly requirements:

SN74LVC821ADW (Tube Packaging): Suitable for low-volume applications, prototype development, and manual assembly processes where individual component handling is required.

SN74LVC821ADWR (Tape & Reel Packaging): Recommended for production-volume manufacturing and automated assembly operations where continuous reel feeding is standard practice.

Both substitute parts are manufactured by Texas Instruments with Active product status, ensuring long-term availability and manufacturing support. The 74LVC series provides ROHS3 compliance, meeting modern environmental and regulatory requirements. Extended lower supply voltage capability (1.65V minimum versus 2V) offers additional design flexibility without compromising compatibility within the original 74LCX operating envelope.

Frequently Asked Questions (FAQ)

Q: Can SN74LVC821ADW and SN74LVC821ADWR be used interchangeably with 74LCX821WMX?

A: Yes. Both parts are functionally equivalent with identical electrical performance, pin configuration, and package dimensions. The difference is packaging format: Tube versus Tape & Reel. Selection depends on assembly method and procurement volume.

Q: What is the difference between the 74LCX and 74LVC series?

A: The 74LVC series is the active production successor to the obsolete 74LCX series. Both share identical functional specifications and pin compatibility. The 74LVC series offers extended lower supply voltage range (1.65V minimum) and current manufacturing support with ROHS3 compliance.

Q: Are there any timing differences between the main part and substitutes?

A: Maximum propagation delay differs slightly: 74LCX821WMX specifies 7ns at 3.3V with 50pF load, while both 74LVC substitutes specify 7.3ns under identical conditions. This 0.3ns difference is within typical circuit margin and does not affect functional compatibility.

Q: What is the input capacitance difference?

A: The 74LCX821WMX has 7 pF input capacitance, while the 74LVC substitutes have 5 pF. Lower input capacitance in the 74LVC series reduces loading on driving circuits, providing a performance advantage.

Q: Are the substitute parts RoHS compliant?

A: Yes. Both SN74LVC821ADW and SN74LVC821ADWR are ROHS3 compliant. The original 74LCX821WMX RoHS status is not specified in available documentation.

Q: Can I mix packaging formats in the same production run?

A: Functionally, yes. However, mixing Tube and Tape & Reel formats in a single assembly process may introduce handling inefficiencies. Standardizing on one packaging format per production batch is recommended for assembly line optimization.

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