Texas Instruments SN74CBT3125CPW

Overview

SN74CBT3125CPW from Texas Instruments is a quad 1-bit FET bus switch IC with TTL-compatible control inputs, 3 Ω typical ON-state resistance, near-zero propagation delay (0.15 ns at 5 V), and bidirectional signal routing for 0–5-V logic levels. It serves as a low-distortion signal gate in USB interface and bus isolation applications.

For engineers reviewing the SN74CBT3125CPW datasheet, SN74CBT3125CPW pinout, SN74CBT3125CPW application, or SN74CBT3125CPW equivalent, key selection criteria include undershoot protection to −2 V, I_off-enabled partial-power-down operation, 5 pF typical OFF-state I/O capacitance, and TSSOP-14 package compatibility with high-density PCB layouts.

Technical Context

This device implements four independent single-pole single-throw (SPST) analog switches using NMOS FETs with integrated undershoot-protection circuitry on both A and B ports. Each switch is controlled by a dedicated OE input that enables bidirectional conduction when low.

It supports mixed-voltage signaling (0.8 V to 5 V) across data I/Os while accepting TTL- or CMOS-level control signals. The I_off feature actively blocks current backflow during power-down, ensuring system-level isolation without external biasing.

Key Specifications

Pinout & Package

TSSOP-14 package (PW), 5.0 mm × 4.4 mm footprint, 1.2 mm max height, 0.65 mm lead pitch, exposed thermal pad not present.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3125CPW, SN74CBTD3384CPW offers greater channel density but reduced undershoot resilience, while TS3A24159RGTR delivers lower resistance at the cost of voltage range and transient protection-making SN74CBT3125CPW the optimal choice for robust 5-V bus isolation with guaranteed −2-V fault tolerance.

Availability

SN74CBT3125CPW is available at Aetrix Electronics and suitable for USB interface design, industrial bus isolation, and low-distortion signal gating requiring stable component supply across automotive, medical, and industrial embedded programs.

Supply support for SN74CBT3125CPW 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 and embedded processing technologies, with over 90 years of innovation in high-reliability interface and signal-path solutions.

The SN74CBT3125C family was designed specifically for high-speed, low-distortion digital signal routing in mixed-voltage systems-emphasizing robustness against electrical transients and seamless interoperability across logic families.

FAQ

What is the maximum undershoot voltage the SN74CBT3125CPW can tolerate on its A and B ports?

The SN74CBT3125CPW provides active undershoot protection up to −2 V on both A and B ports, verified per test conditions in the SCDS122A datasheet. This capability ensures reliable OFF-state isolation during negative transients common in hot-plug interfaces like USB, preventing unintended conduction or latch-up. The protection circuitry remains functional across the full −40°C to 85°C operating temperature range.

Does the SN74CBT3125CPW support partial-power-down operation, and how is it implemented?

Yes, the SN74CBT3125CPW supports partial-power-down operation via its I_off feature. When V_CC = 0 V, the device limits I_off current to 10 µA maximum while maintaining high-impedance isolation between all A and B ports. This prevents damaging back-current flow from live signal lines into a powered-down subsystem, enabling safe mixed-power-state system architecture without external isolation components.

What is the typical ON-state resistance of the SN74CBT3125CPW, and how does it affect signal integrity?

The SN74CBT3125CPW has a typical ON-state resistance (r_on) of 3 Ω at V_CC = 4.5 V and I_O = 30 mA. This low resistance minimizes voltage drop and insertion loss across the switch path, preserving signal amplitude and edge rate in high-speed digital applications. At 100-MHz square waves, measured distortion remains below 3% due to this r_on value combined with 12.5-pF ON-state capacitance.

Can the SN74CBT3125CPW interface directly with 1.8-V and 3.3-V logic while powered from a 5-V supply?

Yes, the SN74CBT3125CPW supports 0–5-V signaling on all data I/O pins regardless of V_CC level, enabling direct interfacing with 1.8-V, 2.5-V, 3.3-V, and 5-V logic families. Its control inputs accept TTL- or CMOS-level voltages (V_IL ≤ 0.8 V, V_IH ≥ 2 V), allowing direct drive from 3.3-V microcontrollers even when V_CC = 5 V-no level-shifting circuitry required.

What package type and dimensions does the SN74CBT3125CPW use, and what are its PCB layout considerations?

The SN74CBT3125CPW uses the TSSOP-14 (PW) package: 5.0 mm × 4.4 mm body, 1.2 mm max height, 0.65 mm lead pitch. Layout requires strict adherence to TI's PW0014A footprint-especially 0.45 mm pad width and 1.5 mm length-with solder mask defined pads and 0.125 mm stencil thickness recommended. Thermal performance relies on standard copper pour; no exposed thermal pad is present.