DM74LS221N Equivalent & Substitute Parts

Part Overview

The DM74LS221N is a monostable multivibrator logic IC manufactured by onsemi, housed in a 16-DIP package with 65 ns propagation delay. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing system maintenance and new design implementations. The part operates within the standard 74LS logic family specifications and is suitable for timing and pulse generation applications requiring through-hole mounting.

Substiute Parts

DM74LS221N

onsemiIn Stock: 2122DM74LS221N Datasheet

Current PartRFQ

SN74LS221N

Texas InstrumentsIn Stock: 2179SN74LS221N Datasheet

DirectRFQ

CD74HCT123E

Texas InstrumentsIn Stock: 2107CD74HCT123E Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the DM74LS221N is determined by the following critical parameters:

• Logic function: Monostable multivibrator with 2 independent circuits
• Package compatibility: 16-DIP (0.300", 7.62mm) through-hole mounting
• Supply voltage range: 4.75 V ~ 5.25 V minimum overlap requirement
• Operating temperature range: Minimum 0°C ~ 70°C coverage
• Propagation delay: Equal to or faster than 65 ns (lower values acceptable for timing-critical applications)
• Output current specifications: 400µA high, 8mA low (or equivalent)

Two substitute parts meet these criteria: the SN74LS221N (direct equivalent from Texas Instruments within the same 74LS family) and the CD74HCT123E (functionally equivalent from the 74HCT family with enhanced performance characteristics).

Parameter Comparison

Engineering Selection Recommendations

SN74LS221N (Direct Equivalent): This part is the primary substitute for the DM74LS221N. Both components belong to the 74LS logic family and share identical electrical specifications within the supply voltage and operating temperature ranges. The SN74LS221N offers improved propagation delay (45 ns versus 65 ns) and maintains active product status with ROHS3 compliance, making it suitable for direct replacement in existing designs without circuit modification.

CD74HCT123E (Functional Equivalent): This part provides enhanced performance characteristics with faster propagation delay (25 ns) and extended operating temperature range (-55°C ~ 125°C). The CD74HCT123E belongs to the 74HCT family and features improved supply voltage tolerance (4.5 V ~ 5.5 V). Output current specifications differ (4mA symmetric versus 400µA/8mA asymmetric), which may require circuit evaluation in current-sensitive applications. This substitute is appropriate for designs requiring higher speed or wider temperature operation.

Both substitutes maintain identical package geometry (16-DIP), pin configuration, and functional circuit topology, ensuring mechanical and electrical compatibility with the original DM74LS221N footprint.

Frequently Asked Questions (FAQ)

Q: Can the SN74LS221N be used as a direct drop-in replacement for the DM74LS221N?

A: Yes. The SN74LS221N is a direct equivalent within the 74LS logic family. Both parts share identical supply voltage ranges (4.75 V ~ 5.25 V), operating temperature specifications (0°C ~ 70°C), package geometry (16-DIP), and output current ratings. The faster propagation delay of the SN74LS221N (45 ns versus 65 ns) is a performance improvement that does not affect compatibility.

Q: What are the key differences between the SN74LS221N and CD74HCT123E?

A: Both are monostable multivibrators with 2 independent circuits in 16-DIP packages. The SN74LS221N belongs to the 74LS family with 45 ns propagation delay, while the CD74HCT123E belongs to the 74HCT family with 25 ns propagation delay. The CD74HCT123E offers extended operating temperature range (-55°C ~ 125°C versus 0°C ~ 70°C) and wider supply voltage tolerance (4.5 V ~ 5.5 V versus 4.75 V ~ 5.25 V). Output current specifications differ: the CD74HCT123E provides symmetric 4mA output, while the 74LS variants provide asymmetric 400µA high and 8mA low.

Q: Are there any compliance or regulatory differences between these parts?

A: The DM74LS221N is RoHS non-compliant and obsolete. Both substitute parts (SN74LS221N and CD74HCT123E) are ROHS3 compliant and carry active product status. All three parts are REACH unaffected and classified under ECCN EAR99 and HTSUS 8542.39.0001.

Q: Which substitute should be selected for a new design?

A: For new designs, the SN74LS221N is recommended if the original 74LS family specifications are required. The CD74HCT123E is recommended if enhanced speed performance or extended temperature operation is beneficial to the application. Both parts are actively manufactured and readily available.

Q: Does the package geometry remain identical across all three parts?

A: Yes. All three parts use the 16-DIP (0.300", 7.62mm) through-hole package with identical pin configuration and footprint. No PCB layout modifications are required when substituting between these parts.