Texas Instruments SN74HC245DBR

Overview

SN74HC245DBR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in digital systems. It operates from 2 V to 6 V, delivers ±6 mA output drive at 5 V, exhibits typical propagation delay of 12 ns (CL = 50 pF), and draws ≤80 µA supply current - enabling low-power, noise-resilient bus isolation in PC and server motherboard interconnects.

For engineers reviewing the SN74HC245DBR datasheet, SN74HC245DBR pinout, SN74HC245DBR application, or SN74HC245DBR equivalent, key selection criteria include its 20-pin SSOP package, DIR/OE dual-control logic, 3-state bus isolation capability, and compatibility with LSTTL loads up to 15 units - critical for legacy-to-modern voltage-level bridging and hot-swap-capable backplane interfaces.

Technical Context

The SN74HC245DBR implements a CMOS-based octal transceiver architecture with independent direction (DIR) and output-enable (OE) controls, supporting true bidirectional data flow without internal latching. Its logic diagram confirms symmetrical A↔B channel routing, where DIR selects transmission direction and OE forces all outputs into high-impedance state.

It features slow edge rates to suppress output ringing, operates across industrial temperature range (–40°C to +85°C), and maintains stable switching characteristics over 2–6 V supply - making it suitable for mixed-voltage bus interfacing where signal integrity and power efficiency are jointly prioritized.

Key Specifications

Pinout & Package

SN74HC245DBR uses a 20-pin SSOP (Shrink Small Outline Package) with 7.20 mm × 5.30 mm body size, optimized for high-density PCB layouts while maintaining hand-soldering feasibility. Pin pitch is 0.65 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC245APWR and 74ACT245SCX, the SN74HC245DBR uniquely balances 2–6 V interoperability, sub-100 µA quiescent current, and LSTTL load compatibility - making it the preferred choice for mixed-voltage, power-sensitive embedded control planes.

Availability

SN74HC245DBR is available at Aetrix Electronics and suitable for server backplanes, industrial PLCs, and network switch control planes requiring stable component supply across extended product lifecycles.

Supply support for SN74HC245DBR 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 company specializing in analog and embedded processing solutions, with leadership in logic, interface, and power management ICs since 1930.

The SN74HC245DBR belongs to TI's HC (High-Speed CMOS) logic family, engineered for low-power, wide-supply-voltage bus interfacing in commercial and industrial computing infrastructure.

FAQ

What is the maximum capacitive load the SN74HC245DBR can drive reliably?

The SN74HC245DBR is characterized for CL = 50 pF and CL = 150 pF in its switching specifications. At 5 V supply, it maintains tpd ≤26 ns (max) and tt ≤15 ns (max) up to 150 pF. Driving loads beyond 150 pF may increase propagation delay and degrade edge monotonicity; layout best practices (short traces, ground planes) are recommended for >100 pF loads. The SN74HC245DBR datasheet specifies performance limits only up to 150 pF.

Does the SN74HC245DBR support hot-swap operation?

The SN74HC245DBR supports hot-swap operation when OE is held HIGH (disabled) during insertion, preventing bus contention. Its ±3000 V HBM ESD rating and bus-isolation capability allow safe live insertion into powered backplanes. However, TI recommends tying OE to VCC via a pullup resistor during power-up to guarantee high-impedance state before control logic initializes - a requirement explicitly noted in the SN74HC245DBR functional description.

Can the SN74HC245DBR interface 3.3 V and 5 V buses simultaneously?

Yes - the SN74HC245DBR operates from 2 V to 6 V and accepts VIH/VIL thresholds scalable with VCC (e.g., VIH = 3.15 V at VCC = 4.5 V). When powered at 5 V, it correctly interprets 3.3 V logic HIGH as valid input and drives 5 V outputs compatible with LSTTL loads. This makes the SN74HC245DBR suitable for bidirectional level translation without external biasing networks.

What is the thermal resistance (RθJA) of the SN74HC245DBR in its SSOP package?

The SN74HC245DBR in DB (SSOP-20) package has a junction-to-ambient thermal resistance (RθJA) of 92.1°C/W, as specified in Section 6.4 of the official datasheet. This value assumes standard JEDEC 2-layer board conditions; actual board layout, copper area, and airflow will affect real-world thermal performance. Derating of maximum ambient temperature is required above 70°C for continuous operation.

How does the SN74HC245DBR handle unused input pins?

All unused inputs on the SN74HC245DBR - including DIR and OE - must be tied to a defined logic level (VCC or GND) to prevent floating states that cause excessive ICC, oscillation, or unpredictable bus behavior. TI explicitly states this in Section 6.3 and Layout Guidelines (Section 11.1). Leaving DIR or OE unconnected risks unintended direction or enable states, compromising bus isolation - a critical requirement confirmed in the SN74HC245DBR functional modes table.