Texas Instruments SN74CBT3251DBQR

Overview

SN74CBT3251DBQR from Texas Instruments is a 1-of-8 FET multiplexer/demultiplexer IC with TTL-compatible control inputs, 5-Ω typical on-state resistance at V_CC = 5 V, 0.24 ns propagation delay (V_CC = 5 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 in microcontroller GPIO expansion and keypad scanning systems.

For engineers reviewing the SN74CBT3251DBQR datasheet, SN74CBT3251DBQR pinout, SN74CBT3251DBQR application, or SN74CBT3251DBQR equivalent, this page delivers verified electrical specs, SSOP-16 package mapping, functional mode table alignment, real-world use value for signal gating, and two validated alternative parts with documented technical and application differences.

Technical Context

The SN74CBT3251DBQR implements an 8-channel analog/digital switch matrix using low-threshold CMOS FETs, enabling bidirectional signal flow between A and any selected B_n port. Its internal binary decoder interprets S0–S2 as a 3-bit address to activate exactly one channel when OE is low; all channels disconnect when OE is high.

It operates with TTL-level control inputs (V_IL ≤ 0.8 V, V_IH ≥ 2 V) across 4 V–5.5 V supply, supports 0–5 V analog signal swing, and exhibits low crosstalk (< –60 dB typical) and fast enable/disable timing (t_en/t_dis ≤ 6.8 ns at V_CC = 4 V). No external biasing or level-shifting is required for standard logic interfacing.

Key Specifications

Pinout & Package

SN74CBT3251DBQR uses a 16-pin Shrink Small-Outline Package (SSOP-DBQ) with 0.65 mm lead pitch, 3.90 mm × 4.90 mm body size, and 1.75 mm maximum height. Pin 1 is located at the top-left corner with a molded index notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3251DBQR, SN74CBT3257DBQR offers identical performance per channel but halves channel count per package, increasing board area for 8-signal systems; CD74HC4051M96 trades speed and low r_ON for broader supply flexibility and lower quiescent current-making it viable only in non-critical timing or high-voltage analog contexts.

Availability

SN74CBT3251DBQR is available at Aetrix Electronics and suitable for industrial automation, digital radio front-ends, and microcontroller-based keypad interfaces requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74CBT3251DBQR 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 technologies, with over 90 years of innovation in high-reliability components.

The SN74CBT3251DBQR belongs to TI's CBT (Crossbar Bus Technology) family of high-speed FET switches, designed specifically for low-latency, low-distortion signal routing in digital and mixed-signal systems where timing integrity and analog fidelity are critical.

FAQ

What is the maximum continuous current per channel for SN74CBT3251DBQR?

The SN74CBT3251DBQR supports up to 128 mA continuous channel current, as specified in Absolute Maximum Ratings. This limit applies individually to each B_n–A path when enabled, and must not be exceeded even with low r_ON. Exceeding this current risks thermal damage or parametric shift, especially at elevated ambient temperatures.

Does SN74CBT3251DBQR support analog signal switching?

Yes, SN74CBT3251DBQR supports analog signals from 0 V to 5 V due to its FET-based architecture and rail-to-rail conduction. Its 5 Ω r_ON and low crosstalk (–60 dB) make it suitable for audio, sensor, and baseband I/Q routing-provided signal slew rates stay within the device's bandwidth limits defined by t_pd and load capacitance.

Can SN74CBT3251DBQR operate with a 3.3 V supply?

No, SN74CBT3251DBQR requires a minimum V_CC of 4 V per Recommended Operating Conditions. At 3.3 V, the internal FETs fail to fully enhance, resulting in elevated r_ON, increased propagation delay, and potential logic misstates on control inputs-violating datasheet specifications and risking system instability.

What is the function of the NC pin (Pin 6) on SN74CBT3251DBQR?

Pin 6 on SN74CBT3251DBQR is a no-connect (NC) terminal with no internal bond wire or circuit connection. It must remain unconnected on the PCB-neither tied to GND nor V_CC-to avoid introducing parasitic capacitance, ESD discharge paths, or mechanical stress that could compromise package integrity or signal performance.

How does OE polarity affect SN74CBT3251DBQR channel behavior?

SN74CBT3251DBQR features active-low OE: channels conduct only when OE is driven logic low (≤0.8 V); all B_n–A paths enter high-impedance state when OE is high (≥2 V). This allows synchronous channel disabling across all 8 paths without altering address lines, simplifying power-gating and bus isolation in multi-device systems.