Texas Instruments SN74CB3T3125PW

Overview

SN74CB3T3125PW from Texas Instruments is a quadruple FET bus switch IC enabling bidirectional 5-V-tolerant level translation between mixed-voltage domains (e.g., 5-V ↔ 3.3-V or 5-V/3.3-V ↔ 2.5-V), with 5 Ω typical ON-state resistance, 4.5 pF typical OFF-state I/O capacitance, and 20 μA maximum supply current - deployed in USB interface isolation and low-power portable equipment.

For engineers reviewing the SN74CB3T3125PW datasheet, SN74CB3T3125PW pinout, SN74CB3T3125PW application, or SN74CB3T3125PW equivalent, key selection criteria include VCC operating range (2.3 V to 3.6 V), Ioff partial-power-down support, 5-V-tolerant I/Os with device powered up or down, and guaranteed near-zero propagation delay (0.15 ns typical).

Technical Context

The SN74CB3T3125PW implements four independent 1-bit bidirectional FET switches, each controlled by an active-low enable (1OE–4OE). Its voltage-translation behavior tracks VCC, enabling output levels to follow the supply rail regardless of input voltage up to 5.5 V.

Each switch supports mixed-mode signaling across 0 V to 5 V (including 0.8 V, 1.2 V, 1.5 V, 1.8 V, 2.5 V, 3.3 V, and 5 V logic levels) and features undershoot clamp diodes on all data and control inputs. The Ioff specification ensures backflow current blocking during partial power-down, providing isolation when VCC = 0 V.

Key Specifications

Pinout & Package

TSSOP-14 (PW) package: 5.00 mm × 4.40 mm body, 0.65 mm lead pitch, surface-mount, moisture-sensitive Level-1 (260 °C peak reflow).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CB3T3125PW, SN74CBT3125PW lacks Ioff and 5-V I/O tolerance - limiting use in hot-swap or mixed-rail systems - while SN74LVC1G3157DBVR offers only single-channel operation and no VCC-tracked output voltage, reducing integration density and translation flexibility.

Availability

SN74CB3T3125PW is available at Aetrix Electronics and suitable for USB interface isolation, multi-voltage bus translation, and low-power portable equipment requiring stable component supply across industrial temperature ranges.

Supply support for SN74CB3T3125PW 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 solutions, with decades of expertise in precision logic and interface ICs.

The SN74CB3T3125PW belongs to TI's CB3T family of low-voltage FET bus switches, engineered specifically for high-speed, low-latency, mixed-voltage domain bridging in portable, industrial, and communications equipment.

FAQ

What is the maximum input voltage allowed on SN74CB3T3125PW I/O pins?

The SN74CB3T3125PW supports input voltages from 0 V to 5.5 V on all data I/O pins (1A–4A, 1B–4B), regardless of VCC state - including when powered down. This 5-V tolerance is specified under absolute maximum ratings and validated per JEDEC JESD78, enabling direct connection to 5-V buses without external clamping.

Does SN74CB3T3125PW support true bidirectional signal flow without direction control?

Yes, SN74CB3T3125PW provides fully bidirectional signal flow between A and B ports with no direction pin or internal buffering. When enabled (OE low), signals pass in either direction with identical electrical characteristics - ron, Cio, and tpd are symmetric - making it ideal for data buses and clock distribution where polarity independence is required.

How does the Ioff feature function in SN74CB3T3125PW during partial power-down?

In SN74CB3T3125PW, Ioff limits current to ≤10 μA when VCC = 0 V and any I/O is biased to 0–5.5 V. This prevents damaging backflow through the FET channel during hot-swap events or system-level power sequencing, ensuring isolation even when upstream logic remains active while the switch is unpowered.

Can SN74CB3T3125PW translate 5-V inputs to 2.5-V outputs using a 2.5-V VCC supply?

Yes - with VCC = 2.5 V, SN74CB3T3125PW translates 5-V inputs to ~2.5-V outputs, supporting mixed-mode operation across 0.8 V, 1.2 V, 1.5 V, 1.8 V, 2.5 V, 3.3 V, and 5 V signaling levels. Output voltage tracks VCC, not input, enabling deterministic level shifting without external resistors or regulators.

What is the recommended bypass capacitor for SN74CB3T3125PW VCC pin?

A 0.1-μF ceramic capacitor placed as close as possible to the VCC pin (Pin 14) and GND (Pin 7) is recommended for SN74CB3T3125PW. This minimizes supply noise and transient voltage droop during fast switching transitions, ensuring stable ron and consistent VOH/VOL performance across temperature and load conditions.