Texas Instruments SN74CB3Q3251DBQR

Overview

SN74CB3Q3251DBQR from Texas Instruments is a 1-of-8 FET multiplexer/demultiplexer bus switch optimized for high-bandwidth, low-voltage operation at 2.5 V and 3.3 V. It features 4 Ω typical ON-state resistance (ron), 500 MHz bandwidth support, 5-V tolerant I/Os, rail-to-rail switching, and bidirectional data flow. It serves as a signal-routing interface in PCI, memory interleaving, and bus isolation applications.

For engineers reviewing the SN74CB3Q3251DBQR datasheet, SN74CB3Q3251DBQR pinout, SN74CB3Q3251DBQR application, or SN74CB3Q3251DBQR equivalent, key selection criteria include its 16-pin SSOP package, 2.3–3.6 V supply range, 3.5 pF OFF-state I/O capacitance, partial-power-down Ioff capability, and compatibility with 0–5 V signaling levels across mixed-voltage systems.

Technical Context

The SN74CB3Q3251DBQR implements an integrated charge-pump circuit to elevate the gate voltage of its pass transistors, enabling low and flat ron over the full input voltage range (0–5.5 V). Its control logic uses three select lines (S0–S2) and one active-low output-enable (OE) to route the A port to one of eight B ports (B1–B8) bidirectionally.

It supports true 5-V tolerance on all I/Os regardless of VCC state-powered up or powered down-and incorporates undershoot clamp diodes on data and control inputs. The device meets JESD 78 Class II latch-up immunity (>100 mA) and JESD 22 ESD ratings (2000-V HBM, 1000-V CDM).

Key Specifications

Pinout & Package

SN74CB3Q3251DBQR is housed in a 16-pin Shrink Small-Outline Package (SSOP), DBQ, with 0.65 mm pitch, 6.2 mm × 4.4 mm body, and 1.75 mm max height. Pin 1 is located in quadrant Q1 per tape-and-reel orientation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDTQS3VH251 and SN74CBTD3384DBQR, SN74CB3Q3251DBQR delivers superior bandwidth, flatter ron, wider supply range (2.3–3.6 V), and guaranteed 5-V I/O tolerance-making it optimal for mixed-voltage, high-speed signal routing where timing margin and voltage flexibility are critical.

Availability

SN74CB3Q3251DBQR is available at Aetrix Electronics and suitable for PCI interface design, memory interleaving systems, differential signal routing, and bus isolation applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SN74CB3Q3251DBQR 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 decades of expertise in high-performance logic and interface solutions.

The SN74CB3Q3251DBQR belongs to TI's CB3Q family of high-bandwidth FET bus switches, engineered specifically for low-latency, low-distortion signal routing in broadband communications, networking infrastructure, and data-intensive computing systems.

FAQ

What is the maximum operating frequency supported by the SN74CB3Q3251DBQR?

The SN74CB3Q3251DBQR supports a maximum switching frequency of 20 MHz for both select (S0–S2) and output-enable (OE) inputs under standard load conditions (RL ≥1 MΩ, CL = 0). Its 500 MHz bandwidth refers to small-signal analog path capability-not digital toggle rate-and enables clean routing of high-speed digital edges and analog waveforms without attenuation or phase shift.

Does the SN74CB3Q3251DBQR require external pull-up resistors on control inputs?

Yes-TI recommends tying OE to VCC through a pull-up resistor during power-up/power-down to ensure a defined high-impedance state. The minimum resistor value depends on the driver's current-sinking capability; typical values range from 4.7 kΩ to 10 kΩ. S0–S2 inputs must also be held at VCC or GND when unused to prevent floating nodes and unintended switching.

Can the SN74CB3Q3251DBQR operate with a 2.5 V supply and interface with 5 V signals?

Yes-the SN74CB3Q3251DBQR operates across 2.3 V to 3.6 V VCC and supports 0–5.5 V signaling on all I/O pins (A and B1–B8), regardless of VCC state. This allows safe 5-V signal routing even when powered at 2.5 V, making it ideal for mixed-voltage system interfaces without external level shifters.

How does the charge pump in the SN74CB3Q3251DBQR improve performance?

The integrated charge pump elevates the gate voltage of the internal FET pass transistors, ensuring strong turn-on across the full 0–5.5 V I/O voltage range. This delivers flat 4 Ω typical ON-state resistance (ron) and near-zero propagation delay (<0.18 ns), unlike non-pumped switches whose ron rises significantly near rail extremes-critical for maintaining signal fidelity in high-speed applications.

Is the SN74CB3Q3251DBQR pin-compatible with other packages in the same family?

No-SN74CB3Q3251DBQR uses a 16-pin SSOP (DBQ) package with 0.65 mm pitch and specific pinout. While functionally identical to SN74CB3Q3251DGVR (TVSOP), SN74CB3Q3251PWR (TSSOP), and SN74CB3Q3251RGYR (VQFN), each has distinct mechanical dimensions, thermal characteristics, and land patterns. PCB layout must match the DBQ footprint; direct substitution requires board redesign.