onsemi MC74F3893AFN

Overview

MC74F3893AFN from ON Semiconductor is a quad Futurebus backplane transceiver with 3-state + open-collector outputs, designed for high-speed bus systems operating at 5 V supply. It features 1 V reduced voltage swing BTL signaling, 100 mA sink capability per I/O pin, and built-in band-gap reference for precise 1.55 V receiver threshold. It drives backplanes with load impedances as low as 10 Ω in IEEE 896/1194.1-compliant systems.

For engineers reviewing the MC74F3893AFN datasheet, pinout, applications, or equivalent options, key selection considerations include BTL-compatible incident-wave switching, glitch-free power-up/down behavior, separate bus ground returns per driver, MOS/TTL-compatible inputs, and compatibility with NSC DS3893A and Signetics 74F3893.

Technical Context

The MC74F3893AFN implements Backplane Transceiver Logic (BTL) with series diodes on drivers to limit capacitive loading (<5 pF) and employs incident-wave switching for sub-8 ns propagation delays. Its precision band-gap reference sets a tightly controlled 1.55 V receiver threshold (±0.075 V), enabling excellent noise immunity despite the 1 V signal swing.

It integrates four independent TTL-compatible receivers (R0–R3) with common RE control and four data inputs (D0–D3) NANDed with DE to gate transmission. All I/O pins support open-collector operation with 100 mA sink current and are rated for 0°C to +70°C ambient operation under 4.5–5.5 V supply.

Key Specifications

Pinout & Package

MC74F3893AFN is housed in a 20-lead PLCC (Plastic Leaded Chip Carrier), case 775-02, with exposed thermal pad not electrically connected. Pin assignments follow standard top-view orientation with corner index mark.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3893A and 74F3893, the MC74F3893AFN offers identical BTL performance and pin compatibility but is optimized for cost-sensitive industrial production with plastic PLCC packaging and ON Semiconductor's extended lifecycle support.

Availability

MC74F3893AFN is available at Aetrix Electronics and suitable for high-speed computer backplanes, industrial real-time control buses, telecom switch fabrics, and avionics data concentrators requiring stable component supply and long-term obsolescence management.

Supply support for MC74F3893AFN 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 is a global semiconductor manufacturer specializing in energy-efficient power management, analog, logic, and custom devices for automotive, industrial, and communications markets.

The MC74F3893AFN belongs to ON Semiconductor's FAST Schottky TTL logic family, engineered specifically for high-reliability, high-speed parallel bus interfaces in mission-critical backplane systems.

FAQ

What is the primary bus standard supported by the MC74F3893AFN?

The MC74F3893AFN is explicitly designed for IEEE 896 and IEEE 1194.1 Futurebus standards. It implements Backplane Transceiver Logic (BTL) with 1 V swing, series-diode drivers, and incident-wave switching to meet those specifications' timing, voltage, and loading requirements. The MC74F3893AFN's 10 Ω drive capability and 1.55 V receiver threshold are aligned to Futurebus physical layer definitions.

Does the MC74F3893AFN require external termination resistors on the bus side?

No, the MC74F3893AFN does not require external series termination because its drivers incorporate internal series diodes that inherently limit capacitive loading to <5 pF and support incident-wave switching. However, proper bus impedance matching (e.g., 10 Ω characteristic impedance) must be maintained on the PCB layout to prevent reflections - termination is handled system-level, not at the IC pin.

How does the MC74F3893AFN achieve glitch-free operation during power-up and power-down?

The MC74F3893AFN uses internal power-on reset circuitry and controlled output stage biasing to hold all outputs in high-impedance or defined inactive states until VCC stabilizes within 4.5–5.5 V. This prevents transient bus contention or false data assertion. The MC74F3893AFN's design ensures Rn outputs remain disabled and I/O pins stay high-Z until valid supply and enable conditions are met.

What is the purpose of the BG (Band-Gap) pin on the MC74F3893AFN?

The BG pin provides access to the internal precision band-gap reference voltage (~1.25 V), which is used to generate the 1.55 V receiver threshold. Though not intended for external use, it requires a 0.1 µF ceramic capacitor to GND (pin 20) for stability. This reference ensures tight threshold tolerance (±0.075 V) across temperature and supply variations, directly improving noise immunity in the MC74F3893AFN's receiver stage.

Can the MC74F3893AFN interface directly with CMOS logic inputs?

Yes, the MC74F3893AFN's Dn, DE, and RE inputs are MOS/TTL compatible, accepting CMOS-high (≥3.5 V) and TTL-high (≥2.0 V) signals. Its Rn outputs deliver TTL-compatible VOH (≥2.5 V) and VOL (≤0.5 V) into 6 mA loads, making them suitable for driving standard CMOS inputs. The MC74F3893AFN thus bridges legacy TTL and modern CMOS subsystems on the same backplane.