SN74LS688NS Equivalent & Substitute Parts

Part Overview

The SN74LS688NS is an 8-bit identity comparator manufactured by Texas Instruments, designed for magnitude comparison applications with active low output. This device is classified as Last Time Buy, indicating discontinued production status. The SN74LS688NS performs equality comparison (A=B function) on two 8-bit inputs and is housed in a 20-SOIC surface mount package.

Due to the Last Time Buy status of the SN74LS688NS, identifying equivalent substitute parts with identical electrical and mechanical specifications is essential for design continuity and procurement planning. Substitute parts must maintain compatibility across all critical parameters including bit width, output logic, supply voltage range, propagation delay, and package configuration.

Substiute Parts

SN74LS688NS

Texas InstrumentsIn Stock: 1150SN74LS688NS Datasheet

Current PartRFQ

SN74LS688NSR

Texas InstrumentsIn Stock: 953SN74LS688NSR Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the SN74LS688NS is determined by strict equivalence across the following critical parameters:

Functional Parameters:

• 8-bit identity comparator architecture
• Active low output logic (A=B function)
• Identical output drive capabilities (400µA high, 24mA low)

Electrical Parameters:

• Supply voltage range: 4.85V ~ 5.25V
• Propagation delay: 23ns maximum @ 5V with 45pF load
• Operating temperature range: 0°C ~ 70°C

Mechanical & Environmental Parameters:

• Package type: 20-SOIC surface mount
• RoHS3 compliance
• Moisture sensitivity level 1

The SN74LS688NSR qualifies as a direct substitute based on identical electrical specifications, functional performance, and package configuration. The primary distinction is packaging format (Tape & Reel versus bulk) and active product status.

Parameter Comparison

Engineering Selection Recommendations

The SN74LS688NSR is the direct equivalent substitute for the SN74LS688NS. Both devices are manufactured by Texas Instruments and share identical electrical performance, functional specifications, and physical package dimensions.

Selection Basis:

The SN74LS688NSR is recommended for new procurement due to its Active product status, ensuring long-term availability and supply chain continuity. The SN74LS688NS, classified as Last Time Buy, has discontinued production and should be transitioned to the SN74LS688NSR for ongoing applications.

Both parts maintain ROHS3 compliance and carry identical environmental certifications. The SN74LS688NSR is supplied in Tape & Reel packaging format, which is standard for automated assembly processes. No electrical or functional modifications are required when transitioning from SN74LS688NS to SN74LS688NSR.

Frequently Asked Questions (FAQ)

Q: Can the SN74LS688NSR directly replace the SN74LS688NS in existing designs?

A: Yes. The SN74LS688NSR is electrically and functionally identical to the SN74LS688NS. All electrical parameters, output characteristics, timing specifications, and package dimensions are equivalent. No circuit modifications are required.

Q: What is the difference between SN74LS688NS and SN74LS688NSR?

A: The primary difference is packaging format. The SN74LS688NS is supplied in bulk packaging, while the SN74LS688NSR is supplied in Tape & Reel format. Additionally, the SN74LS688NSR has Active product status, whereas the SN74LS688NS is Last Time Buy. Electrical and functional specifications are identical.

Q: Why is the SN74LS688NS classified as Last Time Buy?

A: Last Time Buy status indicates that Texas Instruments has discontinued production of this part number. Existing inventory may be available for a limited time, but no new production runs are planned. The SN74LS688NSR is the active replacement.

Q: Are there any compatibility concerns when switching to the SN74LS688NSR?

A: No compatibility concerns exist. The 20-SOIC package dimensions, pin configuration, electrical specifications, and functional behavior are identical. The device is suitable for both manual and automated assembly processes.

Q: What is the significance of the Tape & Reel packaging for the SN74LS688NSR?

A: Tape & Reel packaging is the standard format for high-volume automated assembly operations. It provides better handling efficiency and cost optimization for production environments. The electrical and functional performance remains unchanged.

Q: Are both parts RoHS compliant?

A: Yes. Both the SN74LS688NS and SN74LS688NSR are ROHS3 compliant and carry Moisture Sensitivity Level 1 (Unlimited), indicating no special moisture handling requirements during storage or assembly.