Texas Instruments SN74LVCH245APW

Overview

SN74LVCH245APW from Texas Instruments is an octal bus transceiver with tri-state outputs, designed for bidirectional data translation between 1.65-V and 3.6-V logic domains while accepting 5-V-tolerant inputs. It features bus-hold circuitry on all data inputs, Ioff partial-power-down protection, and a maximum propagation delay of 6.3 ns at 3.3 V. It is used in mixed-voltage server backplanes and PC motherboard I/O expansion interfaces.

For engineers reviewing the SN74LVCH245APW datasheet, SN74LVCH245APW pinout, SN74LVCH245APW application, or SN74LVCH245APW equivalent, key selection criteria include its 1.65–3.6-V supply range, 5-V input tolerance, tri-state control via OE/DIR, bus-hold elimination of external resistors, and TSSOP-20 package compatibility with high-density PCB layouts.

Technical Context

This device implements asynchronous bidirectional data transfer between two 8-bit buses using a single direction-control (DIR) signal and active-low output-enable (OE). Its CMOS input structure supports mixed-mode operation: inputs tolerate up to 5.5 V regardless of VCC, enabling direct interfacing between legacy 5-V peripherals and modern 3.3-V or 1.8-V controllers.

The integrated bus-hold circuit maintains valid logic states on floating A/B port inputs without external biasing, and the Ioff feature ensures zero current flow during power-down sequencing-critical for hot-swap and partial-power-down systems. All outputs exhibit balanced drive strength (±24 mA at 3 V) and low ground bounce (<0.8 V) and undershoot (>2 V) at 3.3 V.

Key Specifications

Pinout & Package

TSSOP-20 (PW) package: 6.50 mm × 4.40 mm body, 0.65-mm lead pitch, surface-mount, moisture-sensitive level 1 (MSL-1).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC245A and 74ALVC245, the SN74LVCH245APW uniquely combines 5-V input tolerance, bus-hold, and Ioff in a single TSSOP-20 package-making it the optimal choice for robust, low-complexity mixed-voltage bus bridging where reliability and ease of use outweigh marginal speed gains.

Availability

SN74LVCH245APW is available at Aetrix Electronics and suitable for server backplanes, PC motherboards, network switch control planes, and industrial PLC communication modules requiring stable component supply across extended temperature and mixed-voltage operating conditions.

Supply support for SN74LVCH245APW 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 specializing in analog, embedded processing, and connectivity technologies, with decades of experience in logic interface solutions for industrial, computing, and communications markets.

The SN74LVCH245A product line delivers robust, low-voltage octal transceivers optimized for mixed-signal system integration-designed specifically to simplify voltage translation, reduce external components, and enhance reliability in high-density digital systems.

FAQ

What is the minimum VCC voltage required for functional operation of the SN74LVCH245APW?

The SN74LVCH245APW is fully specified for operation down to 1.65 V VCC across the full temperature range (–40°C to 125°C). Below this, parameters such as propagation delay, drive strength, and bus-hold current are not guaranteed. At 1.5 V, the device retains data but does not meet AC or DC specifications. Always maintain VCC ≥1.65 V for compliant operation of SN74LVCH245APW.

Does the SN74LVCH245APW require external pullup resistors on its A and B port inputs?

No. The SN74LVCH245APW integrates active bus-hold circuitry on all A1–A8 and B1–B8 inputs, which maintains valid logic states on floating pins without external components. Adding pullup or pulldown resistors is not recommended, as they conflict with the internal bus-hold current and may cause excessive power draw or logic instability in SN74LVCH245APW designs.

Can the SN74LVCH245APW safely interface a 5-V microcontroller with a 1.8-V FPGA?

Yes. The SN74LVCH245APW accepts input voltages up to 5.5 V independent of VCC, allowing direct connection of 5-V outputs to its A or B ports while operating at 1.8 V. Its outputs swing rail-to-rail (0 V to 1.8 V), making it compatible with 1.8-V FPGA I/O standards. This capability is explicitly validated in the SN74LVCH245APW datasheet for mixed-voltage translation.

What is the purpose of the Ioff feature in the SN74LVCH245APW, and when is it active?

The Ioff feature disables all outputs and blocks current flow when VCC = 0 V, preventing damaging back-drive current during live insertion or partial power-down. It activates automatically whenever VCC is unpowered or below ~0.8 V, and remains effective across the full –40°C to 125°C range. This behavior is intrinsic to SN74LVCH245APW silicon design and requires no external control.

How does the OE pin behave during power-up of the SN74LVCH245APW?

During power-up, the OE pin is undefined until VCC reaches ~1.2 V. To ensure outputs remain in high-impedance state, TI recommends tying OE to VCC through a pullup resistor (e.g., 10 kΩ). This guarantees safe startup isolation and prevents bus contention. The SN74LVCH245APW datasheet specifies this practice to avoid unintended driver activation before system initialization completes.