NXP Semiconductors 74LVC646AD,112

Overview

74LVC646AD,112 from NXP Semiconductors is an octal non-inverting bus transceiver with dual 8-bit D-type registers, 3-state outputs, and bidirectional data flow control via DIR and OE inputs. It operates from 1.2 V to 3.6 V, supports 5 V-tolerant I/O, and enables real-time or registered data transfer between A and B buses in mixed-voltage systems such as industrial backplanes and FPGA-to-ASIC interconnects.

For engineers reviewing the 74LVC646AD,112 datasheet, 74LVC646AD,112 pinout, 74LVC646AD,112 application, or 74LVC646AD,112 equivalent, key selection criteria include its dual-clock edge-triggered register architecture (CPAB/CPBA), SAB/SBA multiplexed source selection, 3.6 V max supply, −40 °C to +125 °C temperature range, and SO24 package compatibility with legacy 74LVC layouts.

Technical Context

The 74LVC646AD,112 implements two independent 8-bit register banks (A→B and B→A) with separate clock inputs (CPAB, CPBA) that trigger on LOW-to-HIGH transitions. Data routing is controlled by DIR (direction), OE (output enable active LOW), and SAB/SBA (source select) signals - enabling simultaneous storage and transparent mode operation.

Its 5 V-tolerant inputs/outputs allow direct interfacing between 3.3 V logic domains and legacy 5 V subsystems without level shifters. The device maintains high-impedance I/O states during power-down (VCC = 0 V), supporting partial system shutdown while preserving bus integrity.

Key Specifications

Pinout & Package

74LVC646AD,112 is housed in a plastic small outline package (SO24, SOT137-1) with 24 leads and 7.5 mm body width. Pin 1 is index-marked; pins are arranged in dual rows with GND (pin 12) and VCC (pin 24) positioned for optimal decoupling.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bus transceiver/register applications.

Compared with SN74LVC8T245RHLR and 74AVC16835DGGR, the 74LVC646AD,112 uniquely delivers dual-clock edge-triggered 8-bit register staging in a compact SO24 package - making it the only option for space-constrained designs needing both voltage translation and synchronous bus buffering without external logic.

Availability

74LVC646AD,112 is available at Aetrix Electronics and suitable for industrial backplane interfaces, FPGA-to-MCU bridges, automotive diagnostic hubs, and memory-mapped peripheral interposers requiring stable component supply across extended temperature ranges.

Supply support for 74LVC646AD,112 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, and IoT applications.

The 74LVC646AD,112 belongs to NXP's LVC logic family, engineered for low-voltage operation, mixed-signal interoperability, and robust performance in harsh environments - specifically targeting high-reliability digital interconnects.

FAQ

What is the minimum supply voltage required for reliable operation of the 74LVC646AD,112?

The 74LVC646AD,112 is fully specified down to 1.2 V supply voltage per JEDEC JESD8-12A. At 1.2 V, propagation delay increases to 17 ns and maximum frequency drops to 100 MHz, but all logic functions, 3-state control, and register latching remain functional - enabling ultra-low-power standby modes in battery-operated systems where the 74LVC646AD,112 maintains bus integrity.

Can the 74LVC646AD,112 safely interface a 5 V microcontroller with a 1.8 V FPGA without external level shifters?

Yes - the 74LVC646AD,112 features 5 V-tolerant inputs and outputs, allowing direct connection to 5 V signal sources while operating from a 1.8 V supply. Its VIH/VIL thresholds scale with VCC, ensuring correct logic interpretation across the full 1.2 V–3.6 V range. This eliminates external components in the 74LVC646AD,112 signal path, reducing cost and board space.

How does the 74LVC646AD,112 handle simultaneous read and write operations on the A and B buses?

The 74LVC646AD,112 does not support true simultaneous bidirectional transfer. When OE is LOW and DIR = L, B-bus data drives A-bus outputs; when DIR = H, A-bus data drives B-bus outputs. However, its dual registers allow independent capture: CPAB clocks A→B while CPBA clocks B→A - enabling pipelined handshaking where the 74LVC646AD,112 stores incoming data before routing it on the next cycle.

What is the purpose of the SAB and SBA pins on the 74LVC646AD,112?

SAB (pin 2) selects whether A-bus outputs deliver real-time B-bus data (SAB = L) or stored B-register data (SAB = H). SBA (pin 22) performs the mirrored function for B-bus outputs. These pins enable multiplexed data sourcing - essential for protocols requiring both immediate response and buffered command execution, a capability intrinsic to the 74LVC646AD,112 architecture.

Is the 74LVC646AD,112 pin-compatible with older 74LVC646 variants like the 74LVC646D?

Yes - the 74LVC646AD,112 uses the same SO24 (SOT137-1) package and identical pinout as the original 74LVC646D. Electrical specifications are enhanced (e.g., wider VCC range, improved ESD), but mechanical and logical compatibility is maintained. Designers can drop the 74LVC646AD,112 into existing footprints without layout changes, leveraging its extended temperature range and robustness.