onsemi DM74AS245WMX

Overview

DM74AS245WMX 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 IOL = 48 mA per output, achieves tPLH/tPHL ≤ 7.5 ns, and supports isolation via active-low G and DIR inputs.

For engineers reviewing the DM74AS245WMX datasheet, pinout, applications, or equivalent options, key selection criteria include bidirectional bus direction control, 3-STATE output enable timing (tPZL ≤ 8.5 ns), drive capability into 500 Ω/50 pF loads, CMOS interfacing support at VOH = VCC − 2 V, and SOIC-20 thermal performance (θJA = 76.0°C/W).

Technical Context

The DM74AS245WMX implements eight non-inverting, independently enabled transceiver channels using advanced oxide-isolated, ion-implanted Schottky TTL technology. Direction is controlled by DIR, while output enable/disable is managed by the active-low G input - both inputs are compatible with TTL and CMOS logic levels.

Each channel features PNP inputs to reduce loading, low output impedance (capable of driving 133 Ω terminated lines), and guaranteed switching performance across 0°C to +70°C and full VCC range (4.5–5.5 V). All outputs enter high-impedance state when G is HIGH, fully isolating A and B buses.

Key Specifications

Pinout & Package

DM74AS245WMX is housed in a 20-lead Small Outline Integrated Circuit (SOIC) package per JEDEC MS-013, 0.300" wide (Package Number M20B), with gull-wing leads and standard surface-mount footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AS245N and 74F245PC, DM74AS245WMX offers optimal balance of SOIC-20 surface-mount compatibility, guaranteed CMOS interfacing, and thermal performance (76.0°C/W) for space-constrained industrial control designs.

Availability

DM74AS245WMX is available at Aetrix Electronics and suitable for memory subsystems, microprocessor data buses, digital test equipment backplanes, and industrial PLC I/O expansion requiring stable component supply and long-term obsolescence management.

Supply support for DM74AS245WMX 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 and manufacturer of analog and mixed-signal ICs, acquired by ON Semiconductor in 2016. Known for high-performance TTL, logic, and power products.

The DM74AS245WMX belongs to Fairchild's advanced Schottky TTL logic family, engineered for high-speed, low-power bidirectional bus interfacing in computing and industrial control systems.

FAQ

What is the operating temperature range for DM74AS245WMX?

The DM74AS245WMX is rated for free-air operating temperatures from 0°C to +70°C, as defined in its Recommended Operating Conditions table. This range aligns with commercial-grade logic devices and supports deployment in office, laboratory, and controlled industrial environments. The device's switching characteristics and DC parameters are fully guaranteed across this span, including at VCC = 4.5 V to 5.5 V. Storage temperature extends to −65°C to +150°C, allowing safe long-term inventory storage.

Does DM74AS245WMX support CMOS-level interfacing?

Yes, DM74AS245WMX supports CMOS interfacing via its guaranteed VOH ≥ VCC − 2 V specification at IOH = −2 mA. When VCC = 5.5 V, VOH reaches at least 3.5 V - well above the minimum 3.15 V required for 5 V CMOS HIGH-level recognition. This eliminates the need for external level shifters when connecting to 74HC, 74AC, or other 5 V CMOS devices, simplifying mixed-logic system design.

What is the meaning of "3-STATE outputs independently controlled on A and B buses" in DM74AS245WMX?

This means that the DM74AS245WMX does not provide per-pin 3-STATE control, but rather applies a single 3-STATE enable (G) signal to all A1–A8 and B1–B8 outputs simultaneously. However, the A and B buses remain electrically independent: data flows bidirectionally based on DIR, and both sides enter high-impedance together when G is HIGH. This architecture enables clean bus isolation without requiring separate enable signals for each port.

Can DM74AS245WMX drive a 500 Ω load with 50 pF capacitance?

Yes, DM74AS245WMX switching characteristics - including tPLH and tPHL - are explicitly specified under R1 = R2 = 500 Ω and CL = 50 pF conditions. Its low output impedance and Schottky-clamped outputs ensure clean signal edges into this standardized test load, making it suitable for driving moderately loaded PCB traces, daughterboard interconnects, and legacy backplane stubs without waveform distortion or excessive rise/fall time degradation.

Is DM74AS245WMX pin-compatible with other 74AS245 variants?

DM74AS245WMX is pin-compatible with all 74AS245 variants sharing the 20-lead SOIC (M20B), SOP (M20D), or PDIP (N20A) packages - including SN74AS245N and DM74AS245SJ - as they follow identical JEDEC/EIAJ pinouts. The pin functions (G, DIR, A1–A8, B1–B8) and physical layout are standardized across these variants. Differences lie solely in package type, marking, and thermal characteristics - not pin assignment or logic behavior.