Texas Instruments SN74CB3Q3251PW

Overview

SN74CB3Q3251PW from Texas Instruments is a 1-of-8 FET multiplexer/demultiplexer bus switch optimized for high-bandwidth, low-voltage operation at 2.5 V or 3.3 V. It features bidirectional rail-to-rail signal routing, 4 Ω typical ON-state resistance (ron), 500 MHz bandwidth capability, and 5-V tolerant I/Os with 2.3–3.6 V VCC supply range-enabling use in PCI interface, memory interleaving, and bus isolation applications.

For engineers reviewing the SN74CB3Q3251PW datasheet, SN74CB3Q3251PW pinout, SN74CB3Q3251PW application, or SN74CB3Q3251PW equivalent, key selection criteria include its 16-pin TSSOP (PW) package, Ioff partial-power-down support, 3.5 pF typical OFF-state I/O capacitance, and compatibility with 0–5 V signaling levels across mixed-voltage systems.

Technical Context

The SN74CB3Q3251PW implements an integrated charge-pump circuit to elevate the gate voltage of its pass transistors, ensuring low and flat ron over the full input voltage range (0–5.5 V). This architecture enables near-zero propagation delay (0.12–0.18 ns) and supports rail-to-rail analog/digital signal switching without level-shifting.

Its three select inputs (S0–S2) and active-low output-enable (OE) provide deterministic 1-of-8 path control with bidirectional data flow. The device meets JESD 78 Class II latch-up immunity (>100 mA), includes undershoot clamp diodes on all control inputs, and maintains high-impedance isolation during power-down via Ioff protection.

Key Specifications

Pinout & Package

TSSOP-16 (PW) package: 4.4 mm × 5.0 mm body, 0.65 mm lead pitch, 1.2 mm max height, JEDEC MO-153 compliant. Exposed pad not present. RoHS-compliant NiPdAu lead finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDTQS3VH251 and SN74CBTLV3251PWR, the SN74CB3Q3251PW delivers superior voltage-range flexibility, flatter ron, and true 5-V I/O tolerance during power-off-making it the optimal choice for robust, multi-rail, high-speed bus switching where signal fidelity and system-level safety are prioritized.

Availability

SN74CB3Q3251PW is available at Aetrix Electronics and suitable for PCI interface, memory interleaving, bus isolation, and differential signal gating applications requiring stable component supply and long-term industrial lifecycle support.

Supply support for SN74CB3Q3251PW 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 50 years of innovation in high-reliability signal-path solutions.

The SN74CB3Q3251PW belongs to TI's CB3Q family of high-bandwidth FET bus switches, designed specifically for low-latency, low-distortion signal routing in broadband communications, networking infrastructure, and data-intensive computing platforms.

FAQ

What is the maximum operating frequency supported by the SN74CB3Q3251PW?

The SN74CB3Q3251PW supports a maximum switching frequency of 20 MHz for its control inputs (OE, S0–S2) under specified load conditions (RL ≥ 1 MΩ, CL = 0). Its analog signal path supports up to 500 MHz bandwidth, enabling high-fidelity transmission of fast digital or RF-modulated signals without attenuation or phase distortion. This dual-frequency capability makes SN74CB3Q3251PW suitable for both control-plane and data-plane switching in demanding applications.

Does the SN74CB3Q3251PW support 5-V tolerant I/Os when VCC is unpowered?

Yes, the SN74CB3Q3251PW maintains full 5-V tolerance on all data I/O pins (A and B1–B8) even when VCC = 0 V. This is enabled by its Ioff circuitry and internal protection structures, allowing safe connection to live 5-V buses during power-down sequences. This feature eliminates the need for external blocking diodes or level translators in mixed-voltage hot-swap systems, directly enhancing system reliability and reducing BOM count.

What is the purpose of the NC pin on the SN74CB3Q3251PW?

The NC (No Connection) pin on the SN74CB3Q3251PW is Pin 16 and has no internal bond wire or circuit connection. It must remain unconnected on the PCB-neither tied to VCC, GND, nor left floating-to avoid unintended coupling or mechanical stress on the die. TI explicitly specifies this in the datasheet to prevent layout-induced signal integrity issues or thermal anomalies in the TSSOP-16 package.

How does the charge-pump circuit in the SN74CB3Q3251PW improve performance?

The integrated charge-pump circuit in the SN74CB3Q3251PW elevates the gate voltage of its pass FETs above VCC, ensuring strong turn-on across the entire 0–5.5 V I/O voltage range. This results in a flat 4 Ω typical ON-state resistance (ron) independent of signal swing-unlike non-pumped switches whose ron rises sharply near rail limits. Consequently, SN74CB3Q3251PW delivers consistent propagation delay, minimal THD, and superior signal fidelity in rail-to-rail analog and high-speed digital applications.

Can the SN74CB3Q3251PW be used in analog signal routing applications?

Yes, the SN74CB3Q3251PW is explicitly qualified for analog signal routing due to its rail-to-rail switching capability, low 3.5 pF OFF-state I/O capacitance, flat 4 Ω ron, and absence of signal-dependent distortion mechanisms. It supports continuous DC-coupled signals from 0 V to 5.5 V and preserves waveform integrity for frequencies up to 500 MHz-making SN74CB3Q3251PW appropriate for video switching, RF front-end gating, and precision instrumentation multiplexing where linearity and bandwidth are critical.