Texas Instruments SN74CBT3251DR

Overview

SN74CBT3251DR from Texas Instruments is a 1-of-8 FET multiplexer/demultiplexer in SOIC-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 address (S0–S2) and active-low OE control-used for GPIO expansion and keypad scanning in microcontroller systems.

For engineers reviewing the SN74CBT3251DR datasheet, SN74CBT3251DR pinout, SN74CBT3251DR application, or SN74CBT3251DR equivalent, key selection criteria include its low Ron (5 Ω typ), sub-1 ns propagation delay (tpd = 0.24 ns at 5 V), 50 pF load switching capability, and compatibility with 4–5.5 V supply rails in space-constrained industrial I/O designs.

Technical Context

The SN74CBT3251DR implements an analog-switch-based 1:8 multiplexing architecture using NMOS pass transistors with integrated level-shifting control logic. Its three select lines (S0–S2) decode binary addresses to activate exactly one of eight B-port channels while maintaining signal integrity across 0–5 V analog or digital signals.

Operation requires OE low to enable switching; when OE is high, all channels disconnect with <4 pF off-capacitance. The device uses CMOS input stages with 3.5 pF input capacitance and draws only 3 µA quiescent current, making it suitable for low-power signal routing where bus contention must be avoided.

Key Specifications

Pinout & Package

SN74CBT3251DR is packaged in a 16-pin SOIC (D) body measuring 3.91 mm × 9.90 mm with 1.27 mm pitch. Pin 1 is located at the top-left corner adjacent to the index marking, and the package features gull-wing leads with NIPDAU finish and moisture sensitivity level (MSL) 1 (unlimited floor life at ≤30°C/60% RH).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3244DBR and CD74HC4051M96, the SN74CBT3251DR uniquely combines 5 Ω Ron, sub-nanosecond propagation, and integrated 3-bit decoding-making it optimal for high-speed, low-loss digital signal routing where precise channel selection and minimal latency are critical.

Availability

SN74CBT3251DR is available at Aetrix Electronics and suitable for industrial I/O expansion, microcontroller peripheral interfacing, and sensor signal routing requiring stable component supply and long-term production continuity.

Supply support for SN74CBT3251DR 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 connectivity solutions with emphasis on reliability, longevity, and industrial-grade performance.

The SN74CBT3251DR belongs to TI's CBT (Crossbar Technology) logic family, engineered for ultra-low-resistance, high-speed signal switching in demanding digital and mixed-signal applications.

FAQ

What is the maximum continuous current rating for the SN74CBT3251DR?

The SN74CBT3251DR supports up to 128 mA continuous channel current per switched path, as specified in its Absolute Maximum Ratings table. This limit applies to current flowing between the A port and any selected B port. Exceeding this value risks thermal damage or parametric shift. Designers should verify worst-case current in their application-including transient peaks-and ensure PCB traces and upstream drivers can sustain the load without violating the 128 mA per-channel ceiling. The SN74CBT3251DR maintains safe operation within this bound across its full –40°C to +85°C temperature range.

Does the SN74CBT3251DR support 3.3 V logic control inputs?

No-the SN74CBT3251DR requires TTL-compatible input thresholds: VIH ≥ 2.0 V and VIL ≤ 0.8 V under recommended operating conditions (VCC = 4–5.5 V). While it may function with 3.3 V control signals in many cases, TI does not guarantee reliable switching at 3.3 V because the device lacks dedicated 3.3 V logic-level support. For guaranteed 3.3 V compatibility, consider alternatives like the SN74LVC1G3157 or CD74HC4051. The SN74CBT3251DR is optimized for 5 V systems where its 5 Ω Ron and sub-nanosecond timing deliver maximum benefit.

Can the SN74CBT3251DR be used to route analog audio signals?

Yes-the SN74CBT3251DR supports analog signals from 0 V to VCC (up to 5.5 V) with low on-resistance (5 Ω typ) and low off-capacitance (4 pF), making it suitable for line-level audio routing below 20 kHz. However, its 60 dB crosstalk specification applies at 10 MHz; actual audio-band isolation depends on PCB layout and source impedance. For high-fidelity audio, verify THD+N in-system, as the device introduces no active amplification or buffering. The SN74CBT3251DR is commonly deployed in cost-sensitive audio switch matrices where its speed and bidirectionality outweigh the need for ultra-low noise.

What is the purpose of the NC pin on the SN74CBT3251DR?

Pin 6 of the SN74CBT3251DR is marked NC (No Connect) and has no internal connection to the silicon die. It must remain unconnected on the PCB-neither tied to VCC, GND, nor any signal net. Leaving it floating is acceptable and expected. Routing traces to or placing vias on this pad violates TI's layout guidance and may introduce parasitic coupling or mechanical stress. The NC designation is confirmed in the official pin functions table of the SN74CBT3251DR datasheet (SCDS019M), and this pin serves solely as a structural placeholder in the SOIC-16 package outline.

How does the SN74CBT3251DR behave when OE is left unconnected?

Leaving OE unconnected on the SN74CBT3251DR results in undefined operation: the internal weak pull-down is insufficient to guarantee a logic-low state, risking partial or intermittent channel activation due to noise or leakage. TI explicitly requires OE to be actively driven-either hard-wired to GND for permanent enable or controlled by a GPIO. Floating OE violates Recommended Operating Conditions and may cause increased ICC, signal corruption, or latch-up. Always tie OE to a defined voltage via a 10 kΩ pull-down or direct driver. This requirement applies identically across all variants of the SN74CBT3251DR family.