Texas Instruments SN74CBT3257DR

Overview

SN74CBT3257DR from Texas Instruments is a 4-bit 1-of-2 FET multiplexer/demultiplexer in SOIC-16 package, featuring 5 Ω typical on-state resistance, TTL-compatible control inputs (VIH = 2 V, VIL = 0.8 V), and propagation delay as low as 0.25 ns at VCC = 5 V. It routes bidirectional data between A-port and either B1 or B2 ports under select (S) and output-enable (OE) control, used in high-speed bus switching applications including memory address/data routing and FPGA I/O expansion.

For engineers reviewing the SN74CBT3257DR datasheet, SN74CBT3257DR pinout, SN74CBT3257DR application, or SN74CBT3257DR equivalent, key selection criteria include on-resistance matching across channels, OE/S timing compatibility with 3.3 V/5 V logic families, thermal performance in SOIC packages (θJA = 73°C/W), and absence of DC bias requirements for signal pass-through operation.

Technical Context

This device implements four independent analog/digital bidirectional switches using NMOS pass transistors with integrated level-shifting circuitry to ensure TTL-compatible input thresholds across 4 V–5.5 V supply range. Each switch exhibits matched on-resistance (<7 Ω max) and low charge injection (<10 pC), enabling glitch-free signal routing without DC blocking capacitors.

Control logic follows positive-true enable: OE = L enables switching; S selects B1 (S = L) or B2 (S = H); OE = H forces all A–B paths into high-impedance state regardless of S. No internal pull-ups or pull-downs exist-unused control inputs must be externally tied to VCC or GND per TI SCBA004 guidance.

Key Specifications

Pinout & Package

SN74CBT3257DR uses a 16-pin SOIC (D) package measuring 9.9 mm × 3.91 mm × 1.45 mm (max height), with standard 1.27 mm lead pitch and JEDEC MO-002AC compliance. Pin 1 is located at bottom-left corner when viewed top-side with marking dot present.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar FET multiplexer applications.

Compared with SN74CBT3257DR, SN74CBTD3384D offers higher integration but sacrifices 5 V compatibility and adds translation overhead, while 74LVC1G3157GW trades multi-bit coordination for footprint reduction-neither provides pin-compatible replacement nor identical timing behavior.

Availability

SN74CBT3257DR is available at Aetrix Electronics and suitable for memory bus switching, FPGA I/O expansion, automated test equipment signal routing, and industrial PLC backplane interface applications requiring stable component supply across extended product lifecycles.

Supply support for SN74CBT3257DR 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 company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and communications markets since 1930.

The SN74CBT3257DR belongs to TI's CBT (Crosspoint Bus Transceiver) family, engineered specifically for high-speed, low-distortion bidirectional signal routing in mixed-voltage digital systems without external biasing or level-shifting components.

FAQ

What is the maximum operating temperature range for SN74CBT3257DR?

The SN74CBT3257DR operates reliably from −40°C to +85°C ambient temperature, validated per TI's recommended operating conditions. This range covers industrial environments such as factory automation controllers and outdoor telecom infrastructure where thermal cycling exceeds consumer-grade limits. The SOIC package's θJA of 73°C/W ensures safe junction temperatures under typical 10–20 mA per channel loading.

Does SN74CBT3257DR require external pull-up or pull-down resistors on control inputs?

Yes - SN74CBT3257DR has no internal termination on OE or S inputs. TI explicitly requires unused control inputs to be tied to VCC or GND per application report SCBA004 to prevent floating nodes that cause increased ICC, erratic switching, or ESD susceptibility. For example, if OE is permanently enabled, connect it to GND; if S is fixed to select B1, tie it to GND.

Can SN74CBT3257DR pass analog signals such as audio or sensor outputs?

Yes - SN74CBT3257DR supports analog signal routing due to its bidirectional, rail-to-rail-capable FET switches with flat on-resistance (5–7 Ω) and low charge injection (<10 pC). It preserves signal fidelity for DC-coupled audio paths up to 10 MHz and thermocouple/mV-level sensor outputs, provided VCC ≥ signal peak amplitude and no voltage exceeds absolute maximum ratings (−0.5 V to 7 V).

Is SN74CBT3257DR pin-compatible with other CBT-series multiplexers like SN74CBT3244?

No - SN74CBT3257DR uses a dedicated 16-pin SOIC layout optimized for 4-bit 1-of-2 switching with shared S/OE controls, whereas SN74CBT3244 is an 8-bit bus switch with separate OE per byte and different pin mapping (e.g., no S input). Direct PCB replacement is not possible without layout revision, though functional equivalence exists in specific routing architectures.

What is the significance of the "DR" suffix in SN74CBT3257DR?

The "DR" suffix in SN74CBT3257DR indicates tape-and-reel packaging in the SOIC (D) package variant, containing 2,500 units per reel. This distinguishes it from the tube-packaged SN74CBT3257D (25-unit tubes) and confirms RoHS-compliant lead finish, moisture sensitivity level (MSL) 1 rating, and full production status per TI's packaging addendum - critical for automated SMT assembly planning.