onsemi 74VHC393MX

74VHC393MX Dual 4-Bit Binary Counter Summary and Introduction

The 74VHC393MX from onsemi (originally Fairchild Semiconductor) is a high-speed, dual 4-bit binary counter designed to deliver both performance and power efficiency for modern digital systems. Packaged in a compact 14-lead SOIC (Small Outline Integrated Circuit), this device integrates two independent 4-bit counters within a single IC, enabling 8-bit counting or frequency division functionality. The 74VHC393MX operates on advanced silicon-gate CMOS technology, bridging the speed characteristics of bipolar Schottky TTL logic with the low power requirements inherent to CMOS. Its robust feature set, logic compatibility, and reliable design make it a popular choice for engineers seeking precise binary counting in both new designs and upgrades of existing systems.

Essential Characteristics and Functional Details of 74VHC393MX

With a maximum toggle frequency of 170 MHz at 25°C and a typical supply current (ICC) of only 4 μA, the 74VHC393MX delivers high-speed operation and minimal static power consumption. The device is pin and function compatible with industry-standard 74HC393 models, allowing for seamless substitution in legacy systems or multi-vendor designs.

Power-down protection on all inputs shields the device against destructive voltage transients or mismatches, supporting a wide range of power-supply and input-voltage scenarios. Input protection circuits allow for voltages of 0 V to 7 V to be applied independently of the chip’s actual supply, making the IC safe for use in mixed-voltage systems and ensuring reliable logic-level translation between, for example, 5 V and 3 V domains.

Each of the two counters in the 74VHC393MX is clocked on the negative (falling) edge of its respective CLOCK pulse. A HIGH signal at the CLEAR input will asynchronously reset all associated outputs (Q0–Q3) to logic LOW, regardless of other inputs. This straightforward functionality is essential in clock division, event counting, and frequency scaling applications across programmable logic controllers, instrumentation, and general-purpose computation.

Internal Structure and Logic Functionality of 74VHC393MX

The internal structure of the 74VHC393MX comprises two independent 4-bit binary counters, each featuring its own CLOCK and CLEAR input and four individual parallel outputs. The counters increment their value on each falling edge of the clock, providing four Q outputs per section that can be used to encode a 4-bit binary representation of the count.

By tying together the two internal counters, designers can create an 8-bit binary counting stage or dual, independent 4-bit counters for parallel event monitoring. A logic diagram shows the standard configuration, with cascaded toggling flip-flops responsive to clock transitions, and asynchronous resetting via the CLEAR input. All unused inputs should be tied to known logic levels to prevent floating, as recommended by the technical documentation.

Electrical Specifications and Suggested Operating Parameters of 74VHC393MX

For optimal operation, the 74VHC393MX is specified for the following recommended conditions:

Supply voltage ($V_{CC}$): 2.0 V to 5.5 V

Maximum input voltage: 7 V (independent of supply due to input protection circuitry)

Operating temperature range: typically defined by the SOIC package as -40°C to +85°C

Input logic high/low thresholds optimized for robust noise immunity ($V_{NIH}$/$V_{NIL} \ge 28\% V_{CC}$)

Maximum operating frequency: 170 MHz at standard conditions

Maximum supply current at static conditions: 4 μA (ensuring low static power dissipation)

The device is ESD protected and suitable for interfacing with both 5 V and 3 V logic systems. Exceeding the absolute maximum ratings—such as those for supply voltage, input signals, or storage temperature—may permanently damage the device and affect long-term reliability.

Packaging Variants and Physical Dimensions of 74VHC393MX

The 74VHC393MX is available in a lead-free, JEDEC-compliant 14-lead SOIC package. Mechanical reliability is enhanced by industry-standard dimensions, matching JEDEC MS-012, variation AB, and conforming to ASME Y14.5M-1994 for dimensional tolerancing. Engineers can consult package outline drawings to ensure proper PCB footprint compatibility, with recommendations for land pattern sizes (SOIC127P600X145-14M) provided for manufacturability and quality solder joints.

In addition to the 14-SOIC, the device is also offered in other space-saving formats such as 14-lead SOP (EIAJ Type II, 5.3 mm wide) and 14-lead TSSOP (Thin Shrink Small Outline Package, JEDEC MO-153), expanding layout flexibility for dense board designs or when retrofitting existing hardware.

Possible Substitute or Compatible Models for 74VHC393MX

For engineers evaluating cross-compatibility or availability, the 74VHC393MX can often be replaced or substituted with industry-standard pin- and function-compatible binary counter ICs such as:

74HC393 (High-Speed CMOS, non-VHC, also compatible in many legacy designs)

74LS393 (Low-power Schottky variant, lower speed, higher power)

74AC393 (Advanced CMOS, higher speed)

SN74VHC393 (Texas Instruments, VHC CMOS family)

When substituting, engineers should carefully verify electrical characteristics (such as voltage tolerance, output drive strength, propagation delay, and maximum frequency) to ensure system-level compatibility. Additionally, supply chain considerations such as lead-free status and packaging availability may influence the selection of a replacement model.

Conclusion

The 74VHC393MX stands out as a versatile, high-performance solution for binary counting and frequency division in a variety of digital and mixed-voltage system designs. Its pin-compatible legacy and robust electrical features enable deployment in both new projects and upgrades. Understanding its internal operation, precise electrical specs, and package options empowers engineers and procurement specialists to make confident, informed decisions when selecting a dual 4-bit binary counter for demanding applications.