Texas Instruments SN74F245DBR

Overview

SN74F245DBR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between two 8-bit buses. It features direction control (DIR), output enable (OE), ±48 mA A-side and ±128 mA B-side output drive capability, and operates over 0°C to 70°C. It is used in legacy industrial backplane interfaces and board-level bus isolation.

For engineers reviewing the SN74F245DBR datasheet, SN74F245DBR pinout, SN74F245DBR application, or SN74F245DBR equivalent, key selection considerations include 3-state bus driving strength, propagation delay (1.7–7 ns), SSOP-20 package footprint constraints, and compatibility with 5-V TTL logic families.

Technical Context

The SN74F245DBR implements dual 8-bit bidirectional data paths controlled by a single DIR input and a shared OE input. Its TTL-compatible inputs accept standard 5-V logic thresholds (VIH = 2 V, VIL = 0.8 V), and its outputs support high-current sinking (up to 128 mA on B-side) and sourcing (up to 15 mA on B-side) under 4.5–5.5 V supply.

It uses standard F-series bipolar TTL circuitry with guaranteed switching performance at 5 V and CL = 50 pF, delivering tPLH/tPHL ≤ 7 ns and output-enable/disable delays (tPZH/tPLZ) as low as 1.2 ns. The device provides full bus isolation when OE is high, with off-state leakage < ±1 µA.

Key Specifications

Pinout & Package

SN74F245DBR is housed in a 20-pin Shrink Small-Outline Package (SSOP-20, DB package), measuring 7.4 mm × 5.0 mm with 0.65 mm lead pitch and maximum height of 2.0 mm. It features gull-wing leads and pin 1 index area per JEDEC MO-150.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS245N, SN74F245DBR offers 5× faster propagation and 5× higher drive; versus SN74AHCT245PW, it delivers superior current drive at the cost of higher static power and less noise margin - making SN74F245DBR optimal for timing-critical, high-fanout legacy bus interfaces.

Availability

SN74F245DBR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus isolation, and embedded controller memory expansion requiring stable component supply and long-term obsolescence management.

Supply support for SN74F245DBR 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74F245DBR belongs to TI's 74F TTL logic family, engineered for high-speed, high-drive 5-V digital interfacing in mission-critical industrial and computing infrastructure.

FAQ

What is the maximum clock frequency supported by SN74F245DBR in a bidirectional bus application?

The SN74F245DBR does not operate on a clock signal - it is an asynchronous transceiver. Its usable data rate depends on propagation delay (≤7 ns) and system timing margins. In practice, SN74F245DBR reliably supports bus handshaking protocols up to 10–15 MHz in well-terminated, low-capacitance layouts. For the SN74F245DBR, timing validation must be performed per actual PCB trace length and load capacitance.

Can SN74F245DBR be used with 3.3-V logic systems?

No - SN74F245DBR is a 5-V-only TTL device with absolute maximum VCC of 5.5 V and minimum recommended VCC of 4.5 V. Its input thresholds (VIH = 2 V, VIL = 0.8 V) and output voltages (VOH ≈ 2.4 V @ –3 mA) are incompatible with 3.3-V logic levels. Interfacing SN74F245DBR with 3.3-V systems requires level-shifting circuitry; direct connection risks undervoltage operation or damage.

What is the thermal resistance (θJA) of the SN74F245DBR in its SSOP-20 package?

Texas Instruments does not publish θJA for SN74F245DBR in the DB package in the SDFS010A datasheet. However, based on JEDEC MO-150 SSOP-20 thermal characterization standards and comparable TI F-series devices, typical θJA is approximately 120°C/W on 1-inch² 2-layer board with 1 oz copper. For thermal design using SN74F245DBR, refer to TI's generic SSOP thermal guidelines and validate with IR imaging under worst-case ICC conditions.

Does SN74F245DBR support hot insertion or live bus swapping?

SN74F245DBR is not hot-swap rated. While its 3-state outputs provide isolation when OE is high, the device lacks bus-hold, power-up 3-state, or Ioff protection. Applying VCC before GND or connecting to a live bus may cause latch-up or excessive current due to input clamping diodes. For safe live insertion, SN74F245DBR must be powered and stabilized before enabling OE - always use external current-limiting or sequencing circuitry in hot-swap applications.

How does the drive strength asymmetry (A-side vs. B-side) benefit system design?

The SN74F245DBR provides higher B-side output current (128 mA sink) than A-side (48 mA sink) to match typical system architecture: the B bus usually connects to heavily loaded main backplanes or long traces, while the A bus links to lighter local subsystems. This asymmetry allows optimized signal integrity on both sides without oversizing drivers unnecessarily - reducing power dissipation on the A side and ensuring robust edge rates on the B side. This design is intrinsic to SN74F245DBR and improves overall bus reliability.