Texas Instruments SN74HC245PWR

Overview

SN74HC245PWR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in embedded 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 I/O interfaces.

For engineers reviewing the SN74HC245PWR datasheet, SN74HC245PWR pinout, SN74HC245PWR application, or SN74HC245PWR equivalent, key selection criteria include its 20-pin TSSOP package (6.50 mm × 4.40 mm), DIR/OE dual-control logic for direction and output enable, 3-state bus isolation capability, and compatibility with LSTTL loads (up to 15) without level-shifting circuitry.

Technical Context

The SN74HC245PWR implements CMOS-based bidirectional bus control using a single DIR input to select A→B or B→A data flow, and an active-low OE input to place all outputs in high-impedance state. Its balanced output drive and slow edge rates minimize ringing on transmission lines.

It supports full 2–6 V operation with VIH/VIL thresholds scaling proportionally (e.g., VIH = 3.15 V at VCC = 4.5 V), and guarantees 3-state off-state leakage ≤±0.5 µA at 6 V - critical for maintaining bus integrity during power sequencing or standby modes.

Key Specifications

Pinout & Package

TSSOP-20 (PW) package: 6.50 mm × 4.40 mm body, 0.65 mm lead pitch, surface-mount, RoHS-compliant with NiPdAu lead finish and MSL Level-1 rating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC245PWR, SN74LVC245APWR offers superior speed and drive in 3.3 V domains but sacrifices 5 V compatibility, while 74ACT245SCX delivers tighter timing in pure 5 V environments at the cost of higher power and no mixed-voltage support.

Availability

SN74HC245PWR is available at Aetrix Electronics and suitable for server backplanes, PC chipset interfaces, and network switch control planes requiring stable component supply across extended product lifecycles.

Supply support for SN74HC245PWR 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 logic and interface ICs.

The SN74HC245PWR belongs to TI's HC-series high-speed CMOS logic family, engineered for robust bidirectional bus interfacing in computing, communications, and industrial control systems where voltage flexibility and low static power are essential.

FAQ

What is the maximum operating temperature range for the SN74HC245PWR?

The SN74HC245PWR is rated for operation from –40°C to +85°C ambient temperature, matching commercial-grade requirements for desktop PCs, network switches, and industrial HMIs. This range is validated per JEDEC JESD78 and confirmed in the device's Recommended Operating Conditions table (Section 6.3). The TSSOP-20 package's thermal resistance (RθJA = 99.7°C/W) supports this rating under standard PCB copper pour conditions.

Can the SN74HC245PWR be used for level translation between 3.3 V and 5 V buses?

Yes, the SN74HC245PWR supports true bidirectional level translation between 3.3 V and 5 V domains because its 2–6 V VCC range allows operation at either rail, and its CMOS inputs accept VIH ≥ 70% VCC. When powered at 3.3 V, it reliably interprets 5 V signals as valid HIGH (since 5 V > 3.3 V × 0.7 = 2.31 V), and outputs swing rail-to-rail - making it suitable for unidirectional or direction-controlled translation without external resistors or diodes.

How does the DIR and OE pin interaction affect bus behavior in the SN74HC245PWR?

In the SN74HC245PWR, OE is prioritized over DIR: when OE = HIGH, all A and B pins enter high-impedance regardless of DIR state, fully isolating both buses. When OE = LOW, DIR determines direction - DIR = LOW enables B→A transfer; DIR = HIGH enables A→B transfer. This hierarchy prevents bus contention during power-up, as tying OE to VCC via pull-up ensures default isolation until firmware asserts control.

What is the recommended bypass capacitor for the SN74HC245PWR VCC pin?

Texas Instruments specifies a 0.1 µF ceramic capacitor placed as close as possible to the VCC pin (Pin 20) of the SN74HC245PWR, with short, low-inductance traces to GND (Pin 10). This value is validated in Section 10 of the datasheet for noise suppression across the 2–6 V operating range. For boards with multiple HC devices, paralleling a 1 µF bulk capacitor nearby further stabilizes supply ripple under dynamic switching loads.

Does the SN74HC245PWR require external pull-up or pull-down resistors on DIR or OE?

The SN74HC245PWR does not require external biasing on DIR under normal operation, but OE should be pulled up to VCC via a resistor (1–10 kΩ typical) to ensure high-impedance state at power-up - preventing bus contention before firmware initializes. This recommendation is explicitly stated in Section 8.1 and Figure 9-1 of the datasheet, as the device lacks internal pull-ups. Unused A/B pins must be tied to VCC or GND per Section 11.1.