Texas Instruments SN74ABT620DWR

Overview

SN74ABT620DWR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in 5-V TTL-compatible systems. It features inverted output logic, dual output-enable controls (OEAB and OEBA), high-drive capability (–32 mA IOH / 64 mA IOL), and operates from –40°C to 85°C. Used in backplane interface and memory expansion subsystems requiring bus isolation and data direction control.

For engineers reviewing the SN74ABT620DWR datasheet, SN74ABT620DWR pinout, SN74ABT620DWR application, or SN74ABT620DWR equivalent, key selection criteria include its dual-enable 3-state control architecture, 4.1 ns typical propagation delay (A↔B), ±100 µA input leakage, 97°C/W θJA thermal resistance in SOIC-DW package, and compatibility with legacy 5-V TTL bus environments.

Technical Context

The SN74ABT620DWR implements a dual-control 3-state transceiver architecture where OEAB enables A→B transmission and OEBA enables B→A transmission - both must be low for bidirectional pass-through. Its EPIC-II^B BiCMOS process delivers low ground bounce (<1 V VOLP) and latch-up immunity (>500 mA per JESD 17).

It supports true bus storage: when OEAB and OEBA are simultaneously low and external drivers are tri-stated, all 16 bus lines retain their last logic states via mutual reinforcement. Power-up/down isolation is ensured by pullup on OEBA and pulldown on OEAB per TI application guidance.

Key Specifications

Pinout & Package

SN74ABT620DWR is packaged in a 20-pin SOIC (DW) body with 7.5-mm width, JEDEC MS-013 compliant, RoHS-compliant NiPdAu lead finish, and MSL Level-1 rating (260°C reflow unlimited).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ABT245N and SN74LVC245APW, the SN74ABT620DWR uniquely supports inverted data flow and dual-enable bus storage - making it irreplaceable in legacy 5-V systems requiring hold-state retention and polarity-aligned interfacing without added logic.

Availability

SN74ABT620DWR is available at Aetrix Electronics and suitable for industrial backplane routing, memory expansion subsystems, and legacy bus bridging applications requiring stable component supply and long-term obsolescence management.

Supply support for SN74ABT620DWR 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

Texas Instruments is a global semiconductor leader delivering analog, embedded processing, and logic solutions with emphasis on reliability, longevity, and industrial-grade performance.

The SN74ABT620DWR belongs to TI's ABT logic family - engineered for high-speed, high-drive 5-V TTL-compatible bus interfacing in mission-critical industrial and communications infrastructure.

FAQ

What is the function of OEAB and OEBA on the SN74ABT620DWR?

The SN74ABT620DWR uses OEAB to control data flow from A bus to B bus (low enables), and OEBA to control flow from B bus to A bus (low enables). When both are low, bidirectional transfer occurs; when both are high, all outputs enter high-impedance state. This dual-enable scheme enables bus isolation and unique storage mode operation - a defining feature of the SN74ABT620DWR not found in standard transceivers.

Does the SN74ABT620DWR support 3.3-V operation?

No, the SN74ABT620DWR is specified only for 4.5 V to 5.5 V operation per its recommended conditions. It is not 3.3-V tolerant: applying 3.3-V logic signals to its inputs may result in marginal VIH/VIL margins, and VCC below 4.5 V violates datasheet operating limits. For 3.3-V systems, consider SN74LVC245APW - but note it is not pin-compatible or functionally equivalent to the SN74ABT620DWR.

What is the purpose of the inverted output logic in the SN74ABT620DWR?

The SN74ABT620DWR provides inverted data at both A and B ports - meaning output = NOT(input). This design matches legacy peripherals requiring complementary strobes or differential signaling pairs, eliminates need for external inverters in timing-critical paths, and enables direct interface with certain memory controllers and bus arbiters that expect inverted acknowledge or ready signals - a key differentiator of the SN74ABT620DWR versus non-inverting alternatives like SN74ABT245N.

How does the SN74ABT620DWR achieve bus storage functionality?

The SN74ABT620DWR achieves bus storage when OEAB and OEBA are both low *and* all external drivers connected to A and B buses are in high-impedance state. In this condition, each output reinforces its corresponding input, locking all 16 bus lines (A1–A8, B1–B8) in their last valid logic states. This behavior is explicitly documented in the SN74ABT620DWR datasheet and requires no external latches - a capability absent in most octal transceivers including SN74ABT245N.

What thermal considerations apply to the SN74ABT620DWR in SOIC-DW package?

The SN74ABT620DWR in DW package has a θJA of 97°C/W. At maximum rated IOL = 64 mA per output and worst-case VCC = 5.5 V, power dissipation can reach ~180 mW in static drive - requiring board-level copper pour and airflow if ambient exceeds 70°C. Derating curves in the SN74ABT620DWR datasheet specify safe continuous current vs. temperature; exceeding 85°C ambient risks parametric shift in VOL and propagation delay.