onsemi DM74AS245WM

Overview

DM74AS245WM from Fairchild Semiconductor is an octal bus transceiver with independent 3-STATE control on A and B buses, designed for bidirectional data transfer in memory and microprocessor systems. It operates at VCC = 4.5–5.5 V, delivers ±48 mA output drive, achieves 2 ns minimum propagation delay, and interfaces directly with CMOS logic at VOH = VCC − 2 V.

For engineers reviewing the DM74AS245WM datasheet, pinout, applications, or equivalent options, key selection factors include its dual-directional DIR-controlled data flow, independent G-enabled 3-STATE outputs per bus, guaranteed switching performance across 0°C to 70°C, and SOIC-20 (M20B) package compatibility with high-density PCB layouts.

Technical Context

The DM74AS245WM implements non-inverting bidirectional data transfer using advanced oxide-isolated, ion-implanted Schottky TTL process. Direction is controlled by the DIR input, while the G input independently enables or disables both A and B bus drivers/receivers into high-impedance state.

It guarantees switching characteristics into 500 Ω/50 pF loads, supports terminated transmission lines down to 133 Ω, and features PNP inputs to reduce loading on upstream logic-enabling reliable operation in asynchronous bus architectures with mixed TTL/CMOS interfacing requirements.

Key Specifications

Pinout & Package

DM74AS245WM is housed in a 20-lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013 compliant, 0.300-inch body width (Package Number M20B).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AS245N and 74F245PC, the DM74AS245WM uniquely balances SOIC-20 space efficiency, guaranteed CMOS interfacing, and thermal performance (76.0°C/W), making it optimal for high-density commercial embedded systems operating across full 0°C–70°C range.

Availability

DM74AS245WM is available at Aetrix Electronics and suitable for memory bus interface, microprocessor data path, and industrial controller upgrade applications requiring stable component supply and long-term obsolescence management.

Supply support for DM74AS245WM 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

Fairchild Semiconductor was a U.S.-based designer of high-performance analog and logic ICs, acquired by ON Semiconductor in 2016; legacy products like DM74AS245WM remain supported through authorized distribution channels.

The DM74AS245WM belongs to Fairchild's advanced Schottky TTL logic family, engineered specifically for high-speed, low-noise bidirectional bus interfacing in commercial-grade computing and control systems.

FAQ

What is the maximum operating temperature range for the DM74AS245WM?

The DM74AS245WM is specified for operation from 0°C to +70°C ambient temperature. This commercial-grade range is fully validated across all electrical parameters including propagation delay, output drive, and input thresholds. The device's thermal resistance (θJA = 76.0°C/W) allows safe operation at full load within this range when mounted on standard FR-4 PCBs with adequate copper area. Exceeding 70°C may cause parameter drift or reliability degradation.

Does the DM74AS245WM support true bidirectional data flow without external logic?

Yes, the DM74AS245WM supports true bidirectional data flow using only two control inputs: DIR selects direction (A→B or B→A), and G enables/disables all outputs. No external latches, inverters, or glue logic are needed. Both A and B ports are fully bidirectional I/Os with symmetrical drive strength (48 mA sink / 15 mA source) and matched timing (tPLH ≈ tPHL), enabling seamless integration into synchronous or asynchronous bus architectures.

Can the DM74AS245WM interface directly with 5 V CMOS devices?

Yes, the DM74AS245WM is explicitly specified to interface with CMOS at VOH = VCC − 2 V. With VCC = 5 V, VOH is guaranteed ≥3.0 V (min), satisfying the minimum VIH requirement of standard 5 V CMOS. Its VOL ≤0.55 V also meets CMOS VIL limits. This eliminates level shifters in mixed-logic systems - a key design advantage confirmed in the Electrical Characteristics table under VOH conditions.

What is the purpose of the input clamp voltage (VIK = −1.2 V) specification for the DM74AS245WM?

The VIK = −1.2 V specification defines the forward voltage of the internal input ESD protection diode. It ensures that negative transients beyond −1.2 V are safely clamped to GND, protecting the input transistor gates from damage. This is critical in systems subject to hot-plug events, cable discharge, or inductive switching noise. The value is measured at IIN = −18 mA and VCC = 4.5 V, confirming robustness under worst-case fault currents.

Is the DM74AS245WM pin-compatible with the older 74LS245?

Yes, the DM74AS245WM is pin-compatible with the 74LS245 in the SOIC-20 (M20B) footprint - same pin count, spacing, and signal assignment. However, it delivers significantly improved performance: 3× faster propagation (2 ns min vs. 6 ns min), higher output drive (48 mA vs. 24 mA), and guaranteed CMOS interfacing. No PCB changes are required for drop-in replacement, though decoupling and layout practices should follow AS-series guidelines due to faster edges.