Texas Instruments SN74CBT3125CDE4

Overview

SN74CBT3125CDE4 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 undershoot protection up to −2 V on A/B ports. It enables bidirectional signal gating in USB interfaces and bus isolation circuits operating across 0–5-V signaling levels.

For engineers reviewing the SN74CBT3125CDE4 datasheet, SN74CBT3125CDE4 pinout, SN74CBT3125CDE4 application, or SN74CBT3125CDE4 equivalent, key selection criteria include Ioff partial-power-down support, 5 pF OFF-state I/O capacitance, 4–5.5 V supply range, and SOIC-14 package compatibility with legacy board layouts.

Technical Context

This device implements four independent single-pole single-throw (SPST) analog switches using NMOS FETs with integrated undershoot-protection circuitry that clamps A/B port voltages down to −2 V while maintaining high-impedance isolation. Each switch is controlled by a dedicated active-low output-enable (OE) input.

It supports mixed-voltage signaling (0.8 V to 5 V) on data I/Os, accepts TTL/3.3-V/5-V CMOS logic on controls, and features Ioff current limiting (<10 µA at VCC = 0 V) to prevent backflow during partial power-down-critical for hot-swap and system-level power sequencing.

Key Specifications

Pinout & Package

SN74CBT3125CDE4 is housed in a 14-pin SOIC (D) package, 8.75 mm × 3.91 mm footprint, 1.75 mm max height, with standard 1.27 mm lead pitch and RoHS-compliant NiPdAu finish. Pin 1 is located at the top-left corner with notch or index mark.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3125CDE4, SN74CBTD3384CDW offers more bits but sacrifices undershoot resilience and ON-resistance, while 74LVC1G3157GW provides lower cost per channel but lacks multi-bit integration, Ioff, and −2 V protection-making SN74CBT3125CDE4 optimal for robust, compact 4-bit isolation.

Availability

SN74CBT3125CDE4 is available at Aetrix Electronics and suitable for USB interface design, bus isolation in industrial controllers, and low-distortion signal gating in test equipment requiring stable component supply and long-term manufacturability.

Supply support for SN74CBT3125CDE4 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 over 50 years of innovation in high-reliability interface and signal-path ICs.

The SN74CBT3125CDE4 belongs to TI's CBT (Crossbar Bus Transceiver) family, engineered for high-speed, low-distortion signal routing in mixed-voltage digital systems where timing integrity and robustness against transients are critical.

FAQ

What is the maximum undershoot voltage the SN74CBT3125CDE4 can withstand on its A/B ports?

The SN74CBT3125CDE4 provides active undershoot protection up to −2 V on both A and B ports, verified per test conditions in the datasheet (VIKU = −2 V typical). This clamping function remains active even when the switch is disabled, ensuring downstream circuit protection during hot-plug or ESD events without requiring external diodes.

Does the SN74CBT3125CDE4 support partial-power-down operation?

Yes, the SN74CBT3125CDE4 features Ioff circuitry that limits current to ≤10 µA when VCC = 0 V, enabling safe partial-power-down operation. This prevents back-current flow through the switch during power sequencing or hot-swap events-critical for systems with multiple independently powered domains.

Can the SN74CBT3125CDE4 be used for voltage-level translation between different logic families?

Yes, the SN74CBT3125CDE4 supports bidirectional 0–5-V signaling on A/B ports independent of VCC (4–5.5 V), enabling translation between 1.8-V, 2.5-V, 3.3-V, and 5-V logic families. Its 3 Ω ron and 5 pF Cio(OFF) preserve signal fidelity without direction-control overhead.

What is the typical ON-state resistance of the SN74CBT3125CDE4 and how does it affect signal integrity?

The SN74CBT3125CDE4 has a typical ON-state resistance of 3 Ω at VCC = 4.5 V and IO = 30 mA. This low ron minimizes voltage drop and distortion across the switch, maintaining signal amplitude and edge rate-especially important for high-speed digital signals like USB 1.1 or parallel bus clocks.

Is the SN74CBT3125CDE4 pin-compatible with other members of the CBT3125 family?

Yes, SN74CBT3125CDE4 shares identical pinout and functionality with all SOIC-14 variants in the CBT3125 family (e.g., SN74CBT3125CD, SN74CBT3125CDR). Differences are limited to packaging format (tube vs. tape-and-reel) and marking-ensuring drop-in replacement across orderable SKUs.