Texas Instruments SN74AXCH8T245RHLR

Overview

SN74AXCH8T245 from Texas Instruments is an 8-bit dual-supply bus transceiver with configurable voltage translation, tri-state outputs, and bus-hold circuitry. It enables bidirectional level shifting between 0.65 V–3.6 V domains (e.g., 0.9 V processor I/O to 3.3 V peripheral bus), supports up to 380 Mbps (1.8 V → 3.3 V), operates from –40°C to +125°C, and features VCC isolation and partial power-down (I_off) for robust system power management in enterprise SSDs and rack servers.

For engineers reviewing the SN74AXCH8T245 datasheet, SN74AXCH8T245 pinout, SN74AXCH8T245 application, or SN74AXCH8T245 equivalent, key selection considerations include dual-rail supply flexibility (VCCA/VCCB independent), DIR1/DIR2 simultaneous up/down translation capability, bus-hold elimination of external resistors, VCC isolation behavior below 100 mV, and thermal performance (R_θJA = 35°C/W in RHL package).

Technical Context

The SN74AXCH8T245 implements asynchronous bidirectional data flow controlled by two independent direction inputs (DIR1, DIR2), each referenced to VCCA, enabling concurrent A→B and B→A transfers. Its bus-hold circuitry remains active on all A/B ports whenever their respective supply (VCCA or VCCB) is present - independent of DIR/OE state - ensuring stable logic levels on unused inputs without external biasing.

It integrates I_off protection to disable outputs during power-down, preventing current backflow, and activates VCC isolation when either VCCA or VCCB falls below 100 mV, forcing all I/Os into high-impedance. Control pins (DIR1, DIR2, OE) are strictly referenced to VCCA, requiring OE pull-up to VCCA for reliable power-up sequencing.

Key Specifications

Pinout & Package

The SN74AXCH8T245RHLR is housed in a 24-pin VQFN package (5.50 mm × 3.50 mm, 0.5 mm pitch) with exposed thermal pad. Pin 1 is top-left corner (marked via laser etch or mold index), and the thermal pad must be soldered to PCB ground plane for optimal thermal performance (R_θJB = 13.8°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AVCH8T245RHLR and 74AVCH8T245RHLR, the SN74AXCH8T245RHLR delivers higher bandwidth (380 vs. 200 Mbps), dual-direction control (DIR1 + DIR2), and enhanced thermal performance (R_θJA = 35°C/W), making it optimal for next-gen data-intensive infrastructure where speed, flexibility, and thermal headroom are critical.

Availability

SN74AXCH8T245RHLR is available at Aetrix Electronics and suitable for enterprise SSDs, data center switches, rack server baseboards, and building automation controllers requiring stable component supply across extended temperature and voltage ranges.

Supply support for SN74AXCH8T245RHLR 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 over 90 years of innovation in high-reliability electronic components.

The SN74AXCH8T245 belongs to TI's advanced bus transceiver product line, engineered specifically for voltage-domain bridging in high-density, thermally constrained infrastructure equipment such as cloud-scale servers and intelligent edge gateways.

FAQ

What voltage ranges does the SN74AXCH8T245RHLR support on its A and B ports?

The SN74AXCH8T245RHLR supports independent supply voltages from 0.65 V to 3.6 V on both VCCA (A-port reference) and VCCB (B-port reference). This allows direct interfacing between ultra-low-voltage logic (e.g., 0.7 V, 0.8 V, 0.9 V processors) and standard interfaces (1.8 V, 2.5 V, 3.3 V), with verified operation up to 380 Mbps in 1.8 V → 3.3 V translation mode.

How does the bus-hold feature on the SN74AXCH8T245RHLR eliminate external resistors?

The SN74AXCH8T245RHLR integrates active bus-hold circuitry on all 16 data I/Os (A1–A8, B1–B8), which maintains undriven inputs at valid logic-high or logic-low states using internal feedback. This obviates the need for external pull-up or pull-down resistors, reducing BOM cost, PCB area, and potential signal integrity issues - especially critical in high-pin-count, space-constrained applications like SSD modules.

What is the purpose of the DIR1 and DIR2 pins on the SN74AXCH8T245RHLR?

The DIR1 and DIR2 pins on the SN74AXCH8T245RHLR provide independent direction control for two 4-bit groups: DIR1 governs A1–A4 ↔ B1–B4, and DIR2 governs A5–A8 ↔ B5–B8. This enables simultaneous up- and down-translation across the same device - essential for protocols requiring split-bus operation, such as segmented address/data lanes or mixed-voltage debug interfaces in server baseboards.

Does the SN74AXCH8T245RHLR support hot-plug or partial power-down scenarios?

Yes, the SN74AXCH8T245RHLR supports partial power-down via its I_off circuitry, limiting leakage to ±12 µA when either VCCA or VCCB is at 0 V while the other remains powered. Combined with VCC isolation (outputs disabled if either supply <100 mV), this ensures safe hot-plug operation in modular systems like data center line cards and prevents back-current damage during asymmetric power sequencing.

What thermal performance can be expected from the SN74AXCH8T245RHLR in its VQFN package?

In its 24-pin VQFN (RHL) package, the SN74AXCH8T245RHLR achieves R_θJA = 35°C/W (junction-to-ambient) and R_θJB = 13.8°C/W (junction-to-board) when the exposed thermal pad is fully soldered to a 1-in² copper pour. This enables reliable operation at full speed in compact, convection-cooled environments such as 1U server mezzanine cards and industrial edge gateways without forced airflow.