Texas Instruments SN74HCT245NSR

Overview

SN74HCT245NSR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in 5-V logic systems. It features ±6-mA output drive at 5 V, 14-ns typical propagation delay (VCC = 5.5 V), 80-µA maximum ICC, and TTL-compatible inputs - enabling robust signal integrity in ribbon cable and backplane interconnects.

For engineers reviewing the SN74HCT245NSR datasheet, SN74HCT245NSR pinout, SN74HCT245NSR application, or SN74HCT245NSR equivalent, key selection criteria include direction-control logic level compatibility, 3-state isolation timing (ten/tdis ≤ 52 ns), 5-V supply tolerance (4.5–5.5 V), and SO package thermal performance (RθJA = 68.9°C/W).

Technical Context

The SN74HCT245NSR implements a dual-rail CMOS HCT logic family architecture with active-low output enable (OE) and unidirectional direction control (DIR). Its functional modes are defined by OE (isolation when high) and DIR (A→B when high, B→A when low), supporting deterministic bus arbitration without external timing circuitry.

All eight I/O channels share identical electrical characteristics: balanced ±6-mA drive strength, 10-pF input capacitance, and guaranteed 35-mA per-output continuous current. The SO (NS) package places VCC (pin 20) and GND (pin 10) centrally to minimize switching noise coupling across the 20-pin body.

Key Specifications

Pinout & Package

The SN74HCT245NSR uses a 20-pin SOP (Small Outline Package) with 12.60 mm × 5.30 mm body size and gull-wing leads. Thermal resistance is RθJA = 68.9°C/W, suitable for moderate-power density PCB layouts without forced airflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT245DWR and SN74HCT245DBR, the SN74HCT245NSR offers optimal thermal performance (RθJA = 68.9°C/W) in the industry-standard SO package, making it the preferred choice for thermally demanding industrial applications where long-term reliability at 85°C ambient is required.

Availability

SN74HCT245NSR is available at Aetrix Electronics and suitable for factory automation, telecom infrastructure, and industrial storage applications requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for SN74HCT245NSR 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 logic solutions for industrial, automotive, and communications markets.

The SN74HCT245NSR belongs to TI's 74HCT logic family, engineered for robust 5-V mixed-signal interfacing with TTL compatibility, low power, and high noise immunity in harsh industrial environments.

FAQ

What is the maximum operating temperature for the SN74HCT245NSR?

The SN74HCT245NSR is rated for operation from –40°C to +85°C. This industrial temperature range is validated per TI's qualification standards and supports deployment in enclosed control cabinets, outdoor telecom enclosures, and factory-floor equipment without derating. The SO package's thermal metrics ensure junction temperatures remain within safe limits under typical 150-mW power dissipation.

Does the SN74HCT245NSR require external pull-up resistors on DIR or OE pins?

No, the SN74HCT245NSR does not require external pull-up resistors on DIR or OE. Its CMOS inputs draw only ±100 nA (max) at 5.5 V, allowing direct connection to microcontroller GPIOs or logic gates. However, unused inputs must be tied to VCC or GND per TI SCBA004 guidelines to prevent floating states that could cause undefined operation or increased ICC.

Can the SN74HCT245NSR drive a 150-pF load while maintaining timing specifications?

Yes, the SN74HCT245NSR maintains guaranteed timing with CL = 150 pF: tpd ≤ 34 ns (max) at 5.5 V, ten ≤ 67 ns (max), and tdis ≤ 45 ns (max). These values are explicitly specified in Section 6.7 of the datasheet and confirm suitability for driving longer traces, connectors, and multiple LSTTL inputs without timing violations.

Is the SN74HCT245NSR pin-compatible with older 74LS245 devices?

No, the SN74HCT245NSR is not pin-compatible with 74LS245. While both are 20-pin octal transceivers with identical pin numbering, the SN74HCT245NSR uses CMOS HCT logic with different DC characteristics (e.g., VIH = 2 V min vs. LS's 2.0 V min but higher input current), and its 3-state timing (ten/tdis) differs significantly. Direct substitution requires validation of voltage thresholds, loading, and timing margins.

What is the recommended bypass capacitor for the SN74HCT245NSR VCC pin?

Texas Instruments recommends a 0.1-µF ceramic capacitor placed as close as possible to the VCC pin (pin 20) of the SN74HCT245NSR. For systems with multiple VCC pins or high-frequency noise, paralleling a 1-µF capacitor is acceptable. This configuration suppresses supply transients caused by simultaneous switching of all eight outputs, preventing ground bounce and logic errors.