NXP 74HCT4094D: An 8-Bit Serial-In/Serial or Parallel-Out Shift Register with Output Latches

The NXP 74HCT4094D is a high-speed silicon-gate CMOS device that provides robust functionality as an 8-bit serial-in, serial or parallel-out shift register with integrated output latches. This integrated circuit is designed to efficiently manage data flow in a wide array of digital systems, serving as a critical interface between serial data streams and parallel output channels.

At its core, the 74HCT4094D operates by accepting serial data through a single input pin (SER). This data is shifted through the internal eight-stage register on each low-to-high transition of the clock signal (CP). A crucial feature is the output enable pin (OE), which controls the three-state outputs. When OE is held high, the outputs are active; when low, they are forced into a high-impedance state, allowing for efficient bus-oriented applications.

A key differentiator of this shift register is its integrated data latch at each output stage. The state of the latch enable (STR) pin determines when the shifted data is transferred to the output pins. Data can be shifted through the internal register independently while the outputs remain static, held by the latches. This allows the system to update the internal register without causing flickering or glitches on the output lines. The stored data is only presented on the parallel outputs (Q0 to Q7) when STR is driven high. Furthermore, the device provides a serial output (QS) for cascading multiple devices and a QS' output for cascading in high-speed applications, enabling easy expansion to drive more than eight outputs.

The HCT logic family ensures compatibility with both classic TTL levels and modern CMOS logic, making it an ideal choice for legacy system upgrades and new designs. Its high noise immunity and low power consumption are hallmarks of the CMOS technology, while the operation is optimized for a wide voltage range, typically 4.5V to 5.5V.

Typical applications for the 74HCT4094D are extensive. It is perfectly suited for driving LEDs and other displays, functioning as a serial-to-parallel converter in microcontroller interfaces to save valuable I/O pins, and serving in memory bus control and data routing systems.

ICGOOODFIND: The 74HCT4094D is a versatile and reliable solution for expanding output capabilities in digital designs, combining serial input flexibility with latched parallel outputs for stable and glitch-free operation.

Keywords: Shift Register, Serial-to-Parallel Converter, Output Latches, CMOS Logic, Three-State Outputs