Texas Instruments SN74CBT3125CDR

Overview

SN74CBT3125CDR from Texas Instruments is a quad 1-bit FET bus switch IC used for high-speed bidirectional signal gating in mixed-voltage digital systems. It features 3 Ω typical ON-state resistance, 5 pF OFF-state I/O capacitance, −2 V undershoot protection on A/B ports, 4 V to 5.5 V VCC operation, and TTL/CMOS-compatible control inputs - enabling robust USB interface and bus isolation applications.

For engineers reviewing the SN74CBT3125CDR datasheet, SN74CBT3125CDR pinout, SN74CBT3125CDR application, or SN74CBT3125CDR equivalent, key selection criteria include its near-zero propagation delay (0.15 ns at 5 V), Ioff partial-power-down support, 0–5 V data signaling compatibility across 0.8 V to 5 V logic families, and SOIC-14 package thermal performance (θJA = 86°C/W).

Technical Context

This device implements four independent single-pole single-throw (SPST) analog/digital switches using NMOS FETs with integrated undershoot-protection circuitry on both A and B terminals. Each switch is controlled by a dedicated OE input, enabling individual channel enable/disable without affecting others.

It operates as a voltage-transparent bidirectional switch: when OE is low, A and B are connected with minimal ron and Cio(OFF); when OE is high, the switch enters high-impedance isolation with Ioff limiting backflow current during partial power-down. The control inputs accept TTL- or CMOS-level signals and include clamp diodes for undershoot immunity.

Key Specifications

Pinout & Package

SN74CBT3125CDR 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 JEDEC MS-012 AB compliance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3125CDR, SN74CBTD3384CDWR offers higher channel density but sacrifices undershoot resilience and voltage flexibility, while 74LVC1G3157GW,125 trades integration and protection for minimal footprint - making SN74CBT3125CDR optimal for robust, mixed-voltage, quad-gated interconnects.

Availability

SN74CBT3125CDR is available at Aetrix Electronics and suitable for USB interface design, industrial bus isolation, multi-voltage logic bridging, and hot-swap backplane interconnects requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SN74CBT3125CDR 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 industrial and automotive components.

The SN74CBT3125CDR belongs to TI's CBT (Crossbar Bus Transceiver) family, engineered for high-speed, low-distortion signal gating in mixed-voltage digital systems - emphasizing robustness, minimal propagation delay, and safe partial-power-down operation.

FAQ

What is the maximum undershoot voltage the SN74CBT3125CDR can withstand on its A and B ports?

The SN74CBT3125CDR provides active undershoot protection up to −2 V on both A and B ports, verified per test conditions in the datasheet (VCC = 5.5 V, switch OFF). This protects against transient negative excursions during hot-plug events or ESD discharge without requiring external clamping diodes. The protection circuit senses undershoot and forces the switch into a safe OFF state.

Does the SN74CBT3125CDR support true bidirectional signal flow without direction control?

Yes, the SN74CBT3125CDR supports fully bidirectional signal flow - data passes equally from A to B or B to A when the corresponding OE is low. Its FET-based architecture has no inherent directionality, eliminating the need for direction pins or external control logic. This makes SN74CBT3125CDR ideal for shared-bus and analog-signal routing applications.

Can the SN74CBT3125CDR be used with 1.8 V logic while powered from a 5 V supply?

Yes, the SN74CBT3125CDR supports 0–5 V signaling on its A/B I/O ports regardless of VCC (4–5.5 V), enabling direct interface with 1.8 V devices. Its VI/O rating extends to 0 V minimum and 5.5 V maximum, and its 5 pF Cio(OFF) ensures minimal loading on low-voltage nodes. No level shifters are needed when using SN74CBT3125CDR in mixed-voltage systems.

What is the thermal performance of the SN74CBT3125CDR in its SOIC-14 package?

The SN74CBT3125CDR in SOIC-14 (D package) has a junction-to-ambient thermal resistance (θJA) of 86°C/W, measured per JESD 51-7. This value assumes standard JEDEC 2S2P board conditions. For continuous operation at full load, ambient temperature must remain ≤75°C to keep junction temperature below 125°C - consistent with its −40°C to 85°C operating range.

How does the Ioff feature of the SN74CBT3125CDR improve system reliability during power sequencing?

The Ioff feature limits current to ≤10 µA when VCC = 0, preventing damaging backflow from powered I/O lines into an unpowered SN74CBT3125CDR. This enables safe partial-power-down operation - for example, isolating a peripheral bus while the host remains active. It directly enhances system reliability in modular, hot-swap, or multi-rail embedded designs where power domains sequence independently.