SN74AS161D Binary Counter 4-Bit Logic IC

Part Overview

The SN74AS161D is a 4-bit binary counter IC manufactured by Texas Instruments, designed for synchronous counting applications with positive edge triggering. This component operates at a maximum count rate of 40 MHz and is housed in a 16-SOIC surface mount package. The part is currently classified as obsolete, making equivalent substitutes necessary for ongoing production and maintenance applications. The SN74ALS161BD serves as a parametric equivalent that maintains functional compatibility while offering improved availability status.

Substiute Parts

SN74AS161D

Texas InstrumentsIn Stock: 931SN74AS161D Datasheet

Current PartRFQ

SN74ALS161BD

Texas InstrumentsIn Stock: 1374SN74ALS161BD Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

The SN74ALS161BD qualifies as a parametric equivalent to the SN74AS161D based on the following critical substitution criteria:

Matching Parameters:

• Logic Type: Binary Counter (identical function)
• Number of Bits per Element: 4 (identical bit width)
• Number of Elements: 1 (identical element count)
• Direction: Up (identical counting direction)
• Count Rate: 40 MHz (identical maximum frequency)
• Trigger Type: Positive Edge (identical trigger mechanism)
• Reset Type: Asynchronous (identical reset behavior)
• Timing: Synchronous (identical timing architecture)
• Voltage Supply Range: 4.5 V ~ 5.5 V (identical supply voltage)
• Operating Temperature Range: 0°C ~ 70°C (identical temperature range)
• Package Type: 16-SOIC (0.154", 3.90mm Width) (identical physical package)
• Mounting Type: Surface Mount (identical mounting method)

The substitution is valid because all functional, electrical, and mechanical parameters remain constant between the two parts. The primary difference lies in the logic family (AS versus ALS technology) and product availability status.

Parameter Comparison

Engineering Selection Recommendations

The SN74ALS161BD is the appropriate substitute for the SN74AS161D in applications requiring a 4-bit binary counter with 40 MHz count rate capability. Both parts maintain identical electrical specifications, package dimensions, and compliance certifications (ROHS3 Compliant, REACH Unaffected). The SN74ALS161BD offers superior availability status as a Last Time Buy component compared to the obsolete SN74AS161D. Both parts carry MSL Level 1 (Unlimited) moisture sensitivity rating, indicating no special moisture handling requirements during storage or assembly. The 16-SOIC surface mount package ensures direct PCB compatibility without layout modifications.

Frequently Asked Questions (FAQ)

Q: Can the SN74ALS161BD directly replace the SN74AS161D on existing PCBs?

A: Yes. Both parts share identical package dimensions (16-SOIC, 0.154" width), pinout, voltage supply requirements (4.5 V ~ 5.5 V), and functional specifications. No PCB modifications are required.

Q: What is the difference between the 74AS and 74ALS logic families?

A: The 74AS and 74ALS represent different logic family implementations from Texas Instruments. Both deliver identical functional performance for this counter application, including the same 40 MHz count rate and 4-bit resolution. The primary distinction is internal circuit architecture and power consumption characteristics.

Q: Are there any temperature or voltage derating considerations when substituting?

A: No. Both parts operate across the identical temperature range (0°C ~ 70°C) and voltage supply range (4.5 V ~ 5.5 V). Operating conditions remain unchanged.

Q: What is the significance of the product status difference?

A: The SN74AS161D is classified as obsolete, indicating Texas Instruments has discontinued production and support. The SN74ALS161BD carries Last Time Buy status, meaning limited inventory remains available before final discontinuation. For new designs or long-term production, the SN74ALS161BD provides better supply chain continuity.

Q: Do both parts require identical PCB assembly handling?

A: Yes. Both parts carry MSL Level 1 (Unlimited) moisture sensitivity rating, requiring no special moisture control measures during storage, handling, or reflow soldering processes.

Q: Are compliance certifications identical between the two parts?

A: Yes. Both parts are ROHS3 Compliant and REACH Unaffected, meeting identical environmental and regulatory requirements for commercial and industrial applications.