74F191SC

Overview

The onsemi 74F191SC is a synchronous up/down 4-bit binary counter housed in a 16-lead SOIC package. It features asynchronous parallel load and operates within a supply voltage range of +4.5V to +5.5V. The device supports a maximum count frequency of 100 MHz, with propagation delays from clock to output ranging from 3.0 ns to 8.5 ns depending on the operating temperature. It includes Terminal Count and Ripple Clock outputs for cascading applications.

Feature Summary

• Synchronous counting initiated by rising clock edge
• Asynchronous parallel preset capability
• Terminal Count and Ripple Clock outputs for multistage expansion

Applications

• Programmable frequency dividers
• Multistage counter designs using ripple clock configuration
• Synchronous counters utilizing gated carry/borrow logic

Procurement Notes

Verify component authenticity through authorized channels as this part may be obsolete or discontinued. Confirm RoHS compliance status and check for valid datasheet revisions before integration. Ensure that the specific ordering suffix matches the required package type and environmental specifications for your design constraints.

Selection Notes

Select this component for applications requiring high-speed synchronous binary counting with preset functionality. Consider the 16-lead SOIC package for surface mount assembly. Evaluate timing requirements against the specified propagation delays and setup/hold times to ensure reliable operation at the target clock frequencies within the recommended ambient temperature range.

Part Context

This device belongs to the 74F series of logic integrated circuits, characterized by fast switching speeds. It is manufactured by onsemi (formerly Fairchild Semiconductor). The 74F191 serves as a reversible modulo-16 counter, providing a robust solution for digital systems needing precise state tracking and direction control via dedicated input pins.

Replacement Considerations

Public confirmed substitute: SN74LS191D (Texas Instruments). Verify pin compatibility and electrical characteristics before substitution.

FAQ

How is the counting direction controlled?

The direction is determined by the U/D input signal; a HIGH level enables count-up while a LOW level enables count-down.

What is the function of the Ripple Clock output?

The Ripple Clock output simplifies multistage counter design by providing a clock signal for subsequent stages when the Terminal Count condition is met.