Texas Instruments 74LVC8T245RHLRG4

Overview

74LVC8T245RHLRG4 from Texas Instruments is an 8-bit dual-supply non-inverting bus transceiver enabling bidirectional voltage-level translation between 1.65V and 5.5V domains. It features independent VCCA and VCCB rails, 3-state outputs controlled by DIR and OE pins referenced to VCCA, and Ioff support for partial-power-down operation. Used in mixed-voltage interconnects between 1.8V microcontrollers and 3.3V/5V peripherals in industrial PLCs and computing storage subsystems.

For engineers reviewing the 74LVC8T245RHLRG4 datasheet, 74LVC8T245RHLRG4 pinout, 74LVC8T245RHLRG4 application, or 74LVC8T245RHLRG4 equivalent, key selection criteria include configurable dual-rail operation (1.65–5.5V per rail), glitch-free power sequencing, VCC isolation behavior, and VQFN-24 (RHL) thermal performance (RθJA = 48.3°C/W).

Technical Context

The 74LVC8T245RHLRG4 implements a fully asynchronous bidirectional translation architecture: DIR selects data flow direction (A→B when high, B→A when low), while OE enables/disables both output ports simultaneously into high-impedance state. Control inputs (DIR, OE) are referenced solely to VCCA, decoupling control logic from B-side supply variations.

Its dual-rail design supports simultaneous operation at mismatched voltages - e.g., VCCA = 1.8V (A-port logic) and VCCB = 5V (B-port logic) - with guaranteed VIH/VIL thresholds scaling with VCCA. The VCC isolation feature forces all I/Os into high-Z if either VCCA or VCCB drops below 100 mV or floats, preventing backdrive during power-up/down transitions.

Key Specifications

Pinout & Package

VQFN-24 package (RHL), 5.5mm × 3.5mm body, 0.5mm pitch, exposed thermal pad (connected to GND). Optimized for space-constrained industrial and computing modules requiring low thermal resistance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AVC8T245RHLR and TXB0108RHLR, the 74LVC8T245RHLRG4 uniquely combines wide dual-rail flexibility (1.65–5.5V), hardware DIR control for protocol compliance, and VCC-disconnect safety - making it the only option qualified for industrial backplanes with mixed-voltage hot-swap requirements.

Availability

74LVC8T245RHLRG4 is available at Aetrix Electronics and suitable for industrial PLC backplanes, embedded computing memory expansion, flat-panel display timing bridges, and telecom baseband unit data buses requiring stable component supply across extended temperature and mixed-voltage conditions.

Supply support for 74LVC8T245RHLRG4 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 50 years of innovation in industrial, automotive, and communications markets.

The SN74LVC8T245 belongs to TI's LVC logic family, engineered for low-voltage, high-noise-immunity digital interfacing in space- and power-constrained industrial and computing systems.

FAQ

What is the minimum valid VCCA and VCCB voltage for reliable operation of the 74LVC8T245RHLRG4?

The 74LVC8T245RHLRG4 requires VCCA and VCCB to be maintained between 1.65V and 5.5V for full specification compliance. Operation below 1.65V violates recommended conditions and may result in undefined logic thresholds, increased propagation delay variation, or failure to meet Ioff leakage limits. TI does not characterize or guarantee functionality outside this range.

How does the VCC isolation feature behave when VCCA is powered but VCCB is disconnected on the 74LVC8T245RHLRG4?

When VCCB drops below 100 mV or floats while VCCA remains active, the 74LVC8T245RHLRG4 automatically disables all B-port outputs and places them in high-impedance state. A-port outputs remain functional but must be driven by valid logic levels - the device does not disable A-side I/Os unless OE is asserted high.

Can the 74LVC8T245RHLRG4 translate between 1.8V and 5V in both directions simultaneously?

No. The 74LVC8T245RHLRG4 is a unidirectional transceiver per transaction: DIR must be held static during data transfer. Simultaneous A→B and B→A translation requires two devices or a different architecture. For true bidirectional concurrent operation, consider TI's TXS0108E or similar auto-sensing translators.

What is the purpose of the three GND pins (11, 12, 13) on the 74LVC8T245RHLRG4 RHL package?

The three dedicated GND pins on the 74LVC8T245RHLRG4 reduce ground impedance and distribute return current across the VQFN thermal pad footprint. This minimizes ground bounce during simultaneous 8-bit switching, improves noise margin for high-speed edges, and enhances thermal conduction to the PCB ground plane - critical for stable operation above 25MHz.

Is pull-up or pull-down biasing required on unused A-port or B-port pins of the 74LVC8T245RHLRG4?

Yes. All unused A-port and B-port I/Os on the 74LVC8T245RHLRG4 must be actively held at valid logic HIGH (VCCA or VCCB) or LOW (GND) to prevent floating inputs. Floating I/Os increase ICCZ current, cause unpredictable output states, and may induce oscillation or excessive power dissipation - TI explicitly warns against leaving any I/O unconnected.