onsemi DM74AS245SJX

Overview

DM74AS245SJX 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 low-level drive, supports tPLH/tPHL ≤ 7.5 ns propagation delay, and interfaces with CMOS at VOH = VCC − 2 V.

For engineers reviewing the DM74AS245SJX datasheet, pinout, applications, or equivalent options, key selection criteria include bidirectional DIR-controlled data flow, independent G-enabled 3-STATE isolation per bus, guaranteed switching performance across 0°C to 70°C, and compatibility with terminated transmission lines down to 133 Ω.

Technical Context

The DM74AS245SJX implements dual 8-bit non-inverting transceivers with separate DIR (direction) and G (output enable) controls. DIR selects data path direction (A→B or B→A), while G independently disables both A and B outputs into high-impedance state - enabling true bus isolation without requiring matched enable timing.

It uses advanced oxide-isolated, ion-implanted Schottky TTL process, delivering low output impedance (capable of driving 133 Ω terminated lines) and PNP inputs that reduce input loading. Switching characteristics are fully specified into 500 Ω/50 pF loads and guaranteed over full VCC (4.5–5.5 V) and temperature (0°C to 70°C) ranges.

Key Specifications

Pinout & Package

DM74AS245SJX is housed in a 20-lead Small Outline Package (SOP), EIAJ TYPE II, 5.3 mm wide (Package Number M20D). The package is surface-mount, gull-wing leaded, and RoHS-compliant per Fairchild's 2000 specification.

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 DM74AS245SJX offers tighter propagation delay control (7.5 ns max), explicit CMOS interface support (VOH = VCC − 2 V), and SOP packaging suited for high-density layouts - making it optimal for space-constrained, mixed-logic systems requiring robust bus isolation.

Availability

DM74AS245SJX is available at Aetrix Electronics and suitable for memory bus isolation, microprocessor data expansion, and asynchronous backplane interface applications requiring stable component supply and long-term industrial availability.

Supply support for DM74AS245SJX 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 semiconductor company specializing in analog and discrete power products, acquired by ON Semiconductor in 2016. Its legacy logic portfolio remains widely deployed in industrial and legacy systems.

The DM74AS245SJX belongs to Fairchild's advanced Schottky TTL logic family, engineered for high-speed bidirectional data transfer in memory and microprocessor systems where timing predictability and bus isolation are critical.

FAQ

What is the operating temperature range for DM74AS245SJX?

The DM74AS245SJX is specified for operation from 0°C to +70°C ambient temperature. This commercial-grade range aligns with standard microprocessor system environments and is validated across all electrical parameters including propagation delay, VOH/VOL, and ICC. The device does not support extended or industrial temperature grades; operation outside 0°C–70°C may result in undefined timing or output behavior. Always refer to the absolute maximum ratings table for storage and non-operational limits.

Does DM74AS245SJX support true bidirectional data flow without external logic?

Yes, the DM74AS245SJX supports true bidirectional data flow using its dedicated DIR (direction) input. When DIR = LOW, data flows from B bus to A bus; when DIR = HIGH, data flows from A bus to B bus. This single-pin control eliminates the need for external multiplexers or gating logic. Both A and B ports are fully symmetrical in drive strength, timing, and voltage thresholds - confirmed by identical IOL/IOH, tPLH/tPHL, and VOH/VOL specifications for all 16 I/O pins.

Can DM74AS245SJX interface directly with 5 V CMOS devices?

Yes, the DM74AS245SJX is explicitly specified to interface with CMOS at VOH = VCC − 2 V, which yields ≥2.5 V at VCC = 4.5 V - exceeding the minimum VIH requirement of standard 5 V CMOS (typically 3.5 V). While this ensures reliable HIGH-level recognition, designers should verify actual receiver VIH thresholds and consider noise margins. The device's VOL ≤ 0.55 V at IOL = 48 mA also satisfies CMOS VIL requirements under typical loading conditions.

What is the significance of the "X" suffix in DM74AS245SJX?

The "X" suffix in DM74AS245SJX indicates tape-and-reel packaging per Fairchild's ordering convention. It denotes that the device is supplied in EIA-481 compliant carrier tape, optimized for automated SMT placement. The "SJ" base denotes the 20-lead SOP (EIAJ TYPE II, 5.3 mm wide) package; the "X" adds no functional or electrical change - DM74AS245SJX is electrically and mechanically identical to DM74AS245SJ, differing only in packaging format and reel quantity.

How does the G (enable) input affect output behavior in DM74AS245SJX?

The G input is an active-low enable that places all A and B outputs into high-impedance (3-STATE) mode when asserted HIGH, regardless of DIR state or data present on either bus. This provides complete electrical isolation between buses - critical for bus arbitration and hot-swap scenarios. When G = LOW, outputs become active and respond to DIR-controlled direction. Propagation delays for enable/disable (tPZL, tPZH, tPLZ, tPHZ) are guaranteed ≤9.5 ns, ensuring fast bus release without glitches.