74F191SCX Binary Counter IC Equivalent & Substitute Parts

Part Overview

The 74F191SCX is a 4-bit binary counter IC manufactured by onsemi, designed for synchronous counting applications with up/down direction control. This device features a 100 MHz count rate and operates across a 4.5 V to 5.5 V supply voltage range in a 16-SOIC surface mount package.

The 74F191SCX is classified as obsolete. Locating equivalent substitute parts is necessary to support legacy system maintenance, design updates, and production continuity where this component is specified in existing schematics or bill of materials.

Substiute Parts

74F191SCX

onsemiIn Stock: 516774F191SCX Datasheet

Current PartRFQ

SN74LS191D

Texas InstrumentsIn Stock: 1533SN74LS191D Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 74F191SCX is determined by the following critical parameters:

• Package Compatibility: 16-SOIC surface mount package with identical 0.154" (3.90mm) width
• Functional Equivalence: 4-bit binary counter with up/down direction capability and synchronous timing
• Trigger Characteristic: Positive edge trigger requirement
• Electrical Interface: Supply voltage range and operating temperature range compatibility
• Pin Configuration: Identical pinout and signal definitions

The SN74LS191D from Texas Instruments meets these substitution criteria. Both devices share the same 16-SOIC package footprint, identical 4-bit counter architecture with bidirectional counting, synchronous operation, and positive edge triggering. The devices are functionally equivalent at the logic level, with differences limited to speed grade and supply voltage tolerance specifications.

Parameter Comparison

Engineering Selection Recommendations

The SN74LS191D is a direct functional substitute for the 74F191SCX in applications where the reduced count rate of 25 MHz is acceptable. Both devices share identical logic architecture, package footprint, and pinout, enabling direct replacement without PCB redesign.

The primary design consideration is the count rate differential: the 74F191SCX operates at 100 MHz while the SN74LS191D operates at 25 MHz. Applications operating at clock frequencies below 25 MHz will experience no functional impact. Applications requiring operation above 25 MHz must retain the original 74F191SCX or identify alternative high-speed counter solutions.

The SN74LS191D carries a Last Time Buy status, indicating limited future availability. The 74F191SCX is obsolete. For new designs or long-term production requirements, evaluation of current-generation counter ICs is recommended.

Both devices comply with REACH regulations and carry identical export classification (EAR99). Moisture sensitivity level 1 (unlimited) applies to both parts, indicating no special storage or handling requirements.

Frequently Asked Questions (FAQ)

Q: Can the SN74LS191D directly replace the 74F191SCX without PCB modifications?

A: Yes. Both devices use the 16-SOIC package with identical pinout and footprint. No PCB layout changes are required for physical substitution.

Q: What is the primary functional difference between these parts?

A: The count rate differs: 74F191SCX operates at 100 MHz, while SN74LS191D operates at 25 MHz. Logic function, package, and pinout are identical.

Q: Are there supply voltage compatibility concerns?

A: The 74F191SCX accepts 4.5 V to 5.5 V; the SN74LS191D accepts 4.75 V to 5.25 V. Both operate within standard 5 V logic supply ranges. Verify your circuit supply voltage falls within both ranges before substitution.

Q: What is the reset characteristic difference between these parts?

A: The 74F191SCX specifies asynchronous reset; the SN74LS191D does not specify a reset type in the provided data. Verify reset behavior requirements in your application before substitution.

Q: Are both parts RoHS compliant?

A: The SN74LS191D is ROHS3 compliant. RoHS status for the 74F191SCX is not specified in the provided data. Verify compliance requirements for your application.

Q: What is the availability status of these parts?

A: The 74F191SCX is obsolete. The SN74LS191D is Last Time Buy status, indicating limited future availability. Both parts have limited procurement windows.