Texas Instruments SN74CB3Q3251PWR

Overview

SN74CB3Q3251PWR from Texas Instruments is a 1-of-8 FET multiplexer/demultiplexer bus switch optimized for high-bandwidth digital signal routing. It operates from 2.3 V to 3.6 V, delivers 4 Ω typical ON-state resistance (ron), supports 0–5 V bidirectional signaling across all I/Os, and enables rail-to-rail switching in PCI interface and memory interleaving applications.

For engineers reviewing the SN74CB3Q3251PWR datasheet, SN74CB3Q3251PWR pinout, SN74CB3Q3251PWR application, or SN74CB3Q3251PWR equivalent, key selection criteria include its 5-V-tolerant I/Os with partial-power-down Ioff support, 20 MHz maximum switching frequency, and TSSOP-16 package compatibility with high-density PCB layouts.

Technical Context

The SN74CB3Q3251PWR implements an integrated charge-pump circuit to elevate the gate voltage of its pass transistors, ensuring low and flat ron over the full 0–5 V input range and enabling near-zero propagation delay (0.12–0.18 ns). Its control logic uses three select lines (S0–S2) and one active-low output-enable (OE) to route bidirectional data between a common A port and eight B ports (B1–B8).

Designed for signal integrity in high-speed buses, it features 3.5 pF typical OFF-state I/O capacitance, undershoot clamp diodes on all data and control inputs, and JESD 78 Class II latch-up immunity (>100 mA). The device maintains isolation during power-down via Ioff protection, preventing backflow when VCC = 0 V and VI/O = 0–5.5 V.

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, exposed pad not present, RoHS-compliant NiPdAu finish, MSL Level-1 (unlimited reflow).

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDTQS3VH251 and SN74CBTLV3251PWR, the SN74CB3Q3251PWR delivers optimal balance of low ron, Ioff-enabled power management, and broad voltage interoperability-making it ideal for mixed-supply industrial and communications platforms requiring robust hot-swap capability.

Availability

SN74CB3Q3251PWR is available at Aetrix Electronics and suitable for PCI interface, memory interleaving, and bus isolation applications requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for SN74CB3Q3251PWR 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 SN74CB3Q3251PWR belongs to TI's CB3Q family of high-bandwidth FET bus switches, engineered specifically for low-distortion signal gating and mixed-voltage system interconnect in networking, computing, and industrial control.

FAQ

What is the maximum operating temperature range for the SN74CB3Q3251PWR?

The SN74CB3Q3251PWR is rated for continuous operation from –40°C to +85°C ambient temperature. This range is validated across all electrical parameters including ron, tpd, and Ioff, and aligns with industrial-grade reliability requirements. Thermal impedance (θJA) for the TSSOP-16 (PW) package is 108°C/W, so board-level thermal design must ensure junction temperature remains below 125°C under worst-case power dissipation.

Does the SN74CB3Q3251PWR support true bidirectional signal flow?

Yes, the SN74CB3Q3251PWR supports fully bidirectional data flow between the A port and any selected Bx port (B1–B8) when OE is low. There is no intrinsic directionality-the switch conducts equally well from A to Bx or Bx to A, with identical ron, Cio(ON), and propagation delay in both directions. This enables flexible use in shared-bus architectures like memory-mapped I/O or FPGA-to-ASIC interconnect.

Can the SN74CB3Q3251PWR be used with 1.8-V logic inputs?

Yes, the SN74CB3Q3251PWR accepts 1.8-V logic levels on its S0/S1/S2 and OE inputs when VCC ≥ 2.3 V. Per the recommended operating conditions, VIH is 1.7 V min at VCC = 2.3–2.7 V, making 1.8-V CMOS outputs fully compatible. No level-shifter is required, simplifying interface design with low-voltage microcontrollers and FPGAs.

Is the NC pin on the SN74CB3Q3251PWR required to be grounded or left floating?

Pin 5 (NC) on the SN74CB3Q3251PWR has no internal connection and must be left unconnected-neither grounded nor tied to VCC. TI explicitly states "NC – No internal connection" in the top-view package diagram and warns against routing traces or applying bias to this pin, as doing so may compromise signal integrity or cause unintended coupling in high-frequency layouts.

How does the charge pump in the SN74CB3Q3251PWR improve performance compared to standard FET switches?

The integrated charge pump in the SN74CB3Q3251PWR boosts the gate voltage of the pass transistors above VCC, maintaining strong enhancement-mode conduction even when input signals approach VCC or GND. This results in flatter ron across the full 0–5 V range (vs. rising ron near rails in non-pumped devices), enabling consistent 4 Ω typical resistance and sub-0.2 ns propagation delay-critical for high-fidelity signal routing in broadband systems.