Texas Instruments SN74CBT3251DBR

Overview

SN74CBT3251DBR from Texas Instruments is a 1-of-8 FET multiplexer/demultiplexer in SSOP-16 package, featuring 5-Ω typical on-state resistance at 5 V, TTL-compatible control inputs (VIH = 2 V, VIL = 0.8 V), and operation across –40°C to +85°C. It routes one of eight bidirectional B-port channels to a common A port under 3-bit binary select (S0–S2) and active-low OE, enabling compact GPIO expansion in microcontroller-based systems.

For engineers reviewing the SN74CBT3251DBR datasheet, SN74CBT3251DBR pinout, SN74CBT3251DBR application, or SN74CBT3251DBR equivalent, key selection criteria include its low Ron for minimal signal attenuation, fast propagation delay (0.24 ns at 5 V), high channel isolation (>60 dB crosstalk suppression), and compatibility with 4–5.5 V supply rails in space-constrained industrial and consumer interfaces.

Technical Context

The SN74CBT3251DBR implements an analog-switch-based 1:8 multiplexing architecture using NMOS pass transistors with integrated level-shifting circuitry to ensure TTL-compatible input thresholds. Its three select lines (S0–S2) decode directly into eight independent switch paths without external logic.

Operation requires OE low to enable conduction; when OE is high, all switches disconnect with <4 pF off-capacitance per B port. The device supports bidirectional signal flow between A and any selected Bn port, with symmetric on-resistance and voltage handling from 0 V to VCC (max 5.5 V).

Key Specifications

Pinout & Package

SN74CBT3251DBR uses a 16-pin Shrink Small-Outline Package (SSOP-16) with 0.65 mm lead pitch, 5.30 mm × 6.20 mm body size, and 1.75 mm max height - optimized for high-density PCB layouts while maintaining hand-solderability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 1-of-8 analog multiplexer applications.

Compared with SN74CBT3244DBR and CD74HC4051M96, the SN74CBT3251DBR uniquely combines integrated 3-bit decoding, sub-nanosecond speed, and 5 Ω Ron - making it optimal for high-fidelity, low-latency 5 V multiplexing where pin count and timing are critical.

Availability

SN74CBT3251DBR is available at Aetrix Electronics and suitable for factory automation interfaces, digital radio signal routing, and microcontroller GPIO expansion requiring stable component supply and long-term industrial lifecycle support.

Supply support for SN74CBT3251DBR 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 specializing in analog, embedded processing, and connectivity solutions, with decades of expertise in high-speed logic and interface ICs.

The SN74CBT3251DBR belongs to TI's CBT (Crossbar Bus Transceiver) family, designed specifically for low-latency, low-distortion signal routing in 5 V digital and mixed-signal systems.

FAQ

What is the maximum continuous current rating for SN74CBT3251DBR?

The SN74CBT3251DBR supports a continuous channel current of 128 mA per switched path, verified per Absolute Maximum Ratings. This allows robust operation with typical digital I/O loads and moderate analog signal levels without thermal derating at ambient temperatures up to +85°C. Exceeding this limit risks junction overheating and long-term reliability degradation.

Does SN74CBT3251DBR support bidirectional signal flow between A and B ports?

Yes, SN74CBT3251DBR supports fully bidirectional signal routing: when enabled, signals pass equally well from A to selected Bn or from Bn to A. This is inherent to its FET switch architecture and confirmed in the Functional Diagram and Device Functional Modes section of the datasheet.

Can SN74CBT3251DBR operate with a 3.3 V supply?

No, SN74CBT3251DBR requires a minimum supply voltage of 4 V per Recommended Operating Conditions. At 3.3 V, the internal FETs fail to fully enhance, resulting in elevated on-resistance (>20 Ω), increased propagation delay, and unreliable control input recognition - violating datasheet specifications.

What is the purpose of the NC pin (Pin 6) on SN74CBT3251DBR?

Pin 6 is a no-connect (NC) terminal with no internal bond wire or silicon connection. It must remain unconnected on the PCB to prevent mechanical stress on the package, unintended parasitic coupling, or solder bridging that could compromise adjacent signal integrity.

How does SN74CBT3251DBR handle unused select inputs (S0–S2) when only a subset of channels is used?

All select inputs (S0–S2) must be actively driven to valid logic levels - floating inputs cause undefined channel selection and potential shoot-through current. Unused combinations should be tied to fixed VCC or GND per system logic requirements; TI recommends pull-up or pull-down resistors ≤10 kΩ for noise immunity.