onsemi MC74F657AN

Overview

MC74F657AN from ON Semiconductor (formerly Motorola) is an octal bidirectional transceiver with integrated 8-bit parity generator/checker and 3-state outputs, designed for TTL bus-oriented systems. It supports bidirectional data flow between A and B ports, delivers 24 mA sink at A ports and 64 mA sink at B ports, and operates across 0°C to 70°C with 4.5 V–5.5 V supply. Used in legacy industrial backplane and memory expansion interfaces.

For engineers reviewing the MC74F657AN datasheet, pinout, applications, or equivalent options, key selection considerations include guaranteed 3-state timing (tPHZ ≤ 8 ns), high-impedance NPN base inputs (IIL = –40 µA), parity error detection latency (tPHL ≤ 19 ns), and compatibility with FAST Schottky TTL logic families.

Technical Context

The MC74F657AN implements dual-path bidirectional buffering controlled by T/R and OE inputs, with independent parity generation on A-side inputs and real-time parity checking on B-side data. Its internal logic combines functions of MC74F245 (transceiver) and MC74F280A (parity generator) in a single 24-pin package.

It features glitchless outputs during power-up/down, ESD protection >4000 V, and off-state leakage currents as low as ±50 µA. The EVEN/ODD input selects parity mode, while ERROR output asserts low when parity mismatch occurs - all verified under VCC = 4.5–5.5 V and TA = 0–70°C.

Key Specifications

Pinout & Package

MC74F657AN uses a 24-pin plastic DIP (Dual In-line Package), case 724-03, with 0.3-inch body width and through-hole mounting. Pin 1 is top-left corner, pin 24 bottom-right, with GND on pins 7 and 8, VCC on pin 16.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bidirectional transceiver with parity applications.

Compared with MC74F657AN, SN74F657N offers improved timing consistency for synchronous bus arbitration, while 74F657PC provides certified solderability for mission-critical environments - neither is pin-compatible with MC74F657AN's original Motorola lead finish, though footprint and logic behavior match exactly.

Availability

MC74F657AN is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory expansion buses, and test equipment data acquisition systems requiring stable component supply despite end-of-life status.

Supply support for MC74F657AN 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

ON Semiconductor (acquired Motorola's semiconductor business in 2004) is a global supplier of energy-efficient semiconductor components for automotive, industrial, and communications markets.

The MC74F657AN belongs to the legacy FAST Schottky TTL logic family, engineered for high-speed, low-noise bus interfacing in industrial control and instrumentation systems where reliability and timing precision were critical.

FAQ

What is the operating temperature range for MC74F657AN?

The MC74F657AN is specified for operation from 0°C to +70°C ambient temperature. This commercial-grade range aligns with standard industrial control cabinet environments and matches the guaranteed performance window for all DC and AC parameters in the official datasheet. The MC74F657AN maintains full functionality-including 64 mA B-port sink capability and ≤7.5 ns tPHL-within this range under VCC = 4.5 V to 5.5 V.

Does MC74F657AN support both even and odd parity modes?

Yes, the MC74F657AN supports both even and odd parity via the EVEN/ODD input (Pin 12). When HIGH, the device generates and checks even parity across A0–A7 or B0–B7; when LOW, it uses odd parity. The ERROR output asserts LOW only when the received B-port data fails the selected parity check - a behavior confirmed in the FUNCTION TABLE and validated across all operating conditions.

Can MC74F657AN be used with 3.3 V logic systems?

The MC74F657AN is a 5 V-only TTL device and does not support 3.3 V VCC operation. However, its input clamp diodes (VIK = –1.2 V) and low IIL (–40 µA) allow safe interfacing with 3.3 V CMOS outputs using series current-limiting resistors. Direct connection without level-shifting risks damage or incorrect logic thresholds, so the MC74F657AN must be powered at 4.5–5.5 V even when driven by 3.3 V sources.

What is the maximum output short-circuit current rating for MC74F657AN?

The MC74F657AN has a maximum output short-circuit current (IOS) of –225 mA for PARITY, Bn, and ERROR outputs, and –150 mA for A-port outputs - measured at VCC = MAX and VOUT = 0 V. Per datasheet Note 2, only one output may be shorted at a time, and duration must not exceed 1 second. These ratings are validated under worst-case process corners and ensure safe fault handling in bus contention scenarios.

Is MC74F657AN still in production?

No, MC74F657AN is discontinued under Motorola's Lifetime Buy program: last order date was March 31, 1999, and last shipment occurred September 30, 1999. Aetrix Electronics maintains traceable, tested inventory of original MC74F657AN devices for legacy system repair and continuity programs, with full lot traceability and burn-in verification where applicable.