Texas Instruments SN74LVC646APWR

Overview

SN74LVC646APWR from Texas Instruments is an octal bus transceiver and register with 3-state outputs, designed for 1.65-V to 3.6-V V_CC operation. It integrates dual 8-bit buses (A and B), clocked D-type registers, direction control (DIR), output enable (OE), and select controls (SAB/SBA) to support real-time or stored data transfer. Used in mixed-voltage board-level interconnects between 3.3-V and 5-V logic domains.

For engineers reviewing the SN74LVC646APWR datasheet, SN74LVC646APWR pinout, SN74LVC646APWR application, or SN74LVC646APWR equivalent, key selection criteria include its 24-pin TSSOP package, 7.4 ns max propagation delay at 3.3 V, I_off partial-power-down support, 5.5-V tolerant inputs, and bidirectional registered bus management capability.

Technical Context

The SN74LVC646APWR implements two independent 8-bit register banks synchronized to CLKAB and CLKBA, enabling simultaneous or staggered latching of A- or B-bus data. Its DIR/OE/SAB/SBA control matrix supports four distinct bus-management modes: real-time transfer, stored-data transfer, isolation with hold, and register-only storage.

Each port features 5.5-V tolerant CMOS inputs and 3-state outputs with ±24 mA drive strength at 3.0 V, while I_off protection disables outputs during power-down to prevent backflow current. The device operates across –40°C to 85°C and meets JESD 17 latch-up (>250 mA) and JESD 22 ESD standards (2000-V HBM).

Key Specifications

Pinout & Package

TSSOP-24 (PW) package: 7.8 mm × 4.4 mm body, 0.65 mm lead pitch, 1.2 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal registered transceiver applications.

Compared with SN74LVC646ADBR and SN74ALVC164245DLR, the SN74LVC646APWR uniquely combines compact TSSOP packaging, full register-based bus management, and 5.5-V input tolerance - making it optimal for space-constrained, mixed-voltage systems requiring deterministic data staging.

Availability

SN74LVC646APWR is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, PCIe slot interfaces, and test equipment signal routing requiring stable component supply and long-term production continuity.

Supply support for SN74LVC646APWR 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

Texas Instruments is a global semiconductor leader delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and personal electronics markets.

The SN74LVC646APWR belongs to TI's LVC logic family, engineered for low-voltage, high-speed, mixed-signal interfacing in resource-constrained embedded systems requiring robust voltage translation and deterministic bus control.

FAQ

What is the maximum clock frequency supported by the SN74LVC646APWR?

The SN74LVC646APWR supports a maximum clock frequency of 150 MHz across its recommended operating range (V_CC = 1.8 V to 3.3 V). This specification applies to both CLKAB and CLKBA inputs and ensures reliable register capture of A- or B-bus data under worst-case timing conditions including setup/hold margins and propagation delays.

How does the SN74LVC646APWR handle power-down scenarios?

The SN74LVC646APWR incorporates I_off circuitry that automatically disables all outputs when V_CC = 0 V, preventing damaging back-current flow from live buses into the unpowered device. This feature is critical for hot-swap applications and staged power sequencing in multi-rail systems where the SN74LVC646APWR may be powered down independently.

Can the SN74LVC646APWR interface directly with 5-V logic devices?

Yes - the SN74LVC646APWR accepts input voltages up to 5.5 V on all A1–A8 and B1–B8 pins, regardless of V_CC level (1.65–3.6 V). This allows direct connection to 5-V TTL or CMOS outputs without external level-shifting components, while maintaining full 3-state output control and register functionality.

What is the function of the SAB and SBA pins on the SN74LVC646APWR?

The SAB (Select A→B) and SBA (Select B→A) pins determine whether the SN74LVC646APWR outputs real-time or registered data: when SAB = L, B-port reflects live A-bus signals; when SAB = H, B-port outputs data previously latched into the A-register via CLKAB. SBA operates identically for A-port output selection from the B-register.

Is the SN74LVC646APWR pin-compatible with other packages in the same family?

Yes - the SN74LVC646APWR shares identical pinout and signal mapping with all 24-pin variants of the SN74LVC646A family, including SN74LVC646ADBR (SSOP), SN74LVC646ADW (SOIC), and SN74LVC646ANSR (SOP). This allows drop-in replacement across packages without PCB redesign, provided mechanical and thermal constraints permit.