Texas Instruments SN74CBT1G125DCKT

Overview

SN74CBT1G125DCKT from Texas Instruments is a single-channel FET bus switch used for high-speed signal routing in 3.3-V and 5-V digital systems. It features 5-Ω on-state resistance, TTL-compatible OE control input, and bidirectional signal flow between A and B ports. The device operates from –40°C to 85°C and is commonly deployed in data path isolation and hot-swap interface circuits.

For engineers reviewing the SN74CBT1G125DCKT datasheet, SN74CBT1G125DCKT pinout, SN74CBT1G125DCKT application, or SN74CBT1G125DCKT equivalent, key selection criteria include on-resistance matching, propagation delay under 0.35 ns at 4 V, latch-up immunity >250 mA, ESD robustness (2000-V HBM), and SC-70 package thermal performance (θ_JA = 252°C/W).

Technical Context

This device implements a single NMOS transmission gate with no internal level-shifting circuitry. Its OE-controlled switching action provides true bidirectional connectivity when low and high-impedance isolation when high, with no DC bias requirement on A or B terminals. The design supports rail-to-rail analog/digital signal pass-through up to 5.5 V.

Switching behavior is governed by the voltage differential across the channel and gate drive strength of the OE input. Propagation delay is derived from the RC time constant of typical r_on (5–7 Ω) and load capacitance (50 pF), yielding sub-nanosecond timing. Input clamp diodes and JESD 17-compliant latch-up performance enable robust operation in noisy industrial environments.

Key Specifications

Pinout & Package

SN74CBT1G125DCKT uses the SC-70 (DCK) 5-pin surface-mount package (2.4 mm × 1.3 mm × 1.1 mm height), optimized for space-constrained PCB layouts and automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT1G125DCKT, SN74LVC1G3157DCKR offers wider voltage support but sacrifices speed and on-resistance; NC7SZ125P5X provides logic-level buffering but lacks true bidirectional switching-making neither a drop-in replacement without layout or firmware changes.

Availability

SN74CBT1G125DCKT is available at Aetrix Electronics and suitable for PCIe lane isolation, USB 2.0 interface switching, and FPGA I/O expansion requiring stable component supply and long-term industrial availability.

Supply support for SN74CBT1G125DCKT 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 logic solutions with over 90 years of innovation in industrial, automotive, and communications markets.

The SN74CBT family delivers high-speed, low-distortion bus switches for signal integrity–critical applications including computing interconnects, test equipment, and programmable logic interfaces.

FAQ

What is the maximum continuous current rating for SN74CBT1G125DCKT?

The SN74CBT1G125DCKT supports a continuous channel current of 128 mA, verified per absolute maximum ratings. This rating applies across the full operating temperature range (–40°C to 85°C) and ensures reliable conduction without thermal runaway when used within recommended V_CC (4–5.5 V) and r_on (5–7 Ω) limits. Exceeding this current may trigger latch-up or permanent damage.

Does SN74CBT1G125DCKT support bidirectional signal flow?

Yes, SN74CBT1G125DCKT supports fully bidirectional signal flow between its A and B ports. As a passive FET switch, it imposes no directionality-signals pass equally well from A to B or B to A when OE is low. This behavior is confirmed in the functional table and logic diagram, and enables use in bus-sharing, hot-swap, and multiplexing applications without signal inversion or timing asymmetry.

What is the thermal resistance (θ_JA) of SN74CBT1G125DCKT in its SC-70 package?

The SN74CBT1G125DCKT has a junction-to-ambient thermal resistance (θ_JA) of 252°C/W in the SC-70 (DCK) package, as specified in the absolute maximum ratings table. This value assumes standard JEDEC test conditions (single-layer copper, no airflow) and informs thermal design for continuous operation at rated current. Layout improvements (e.g., thermal vias, copper pour) can reduce effective θ_JA in production PCBs.

Can SN74CBT1G125DCKT operate with a 3.3-V supply?

Yes, SN74CBT1G125DCKT operates with a minimum V_CC of 4 V per recommended operating conditions, so it is not rated for 3.3-V-only operation. While some margin exists, TI specifies 4–5.5 V to guarantee TTL-compatible VIH/VIL thresholds, 5-Ω r_on, and sub-ns timing. For 3.3-V systems, consider SN74LVC1G3157DCKR instead-though SN74CBT1G125DCKT remains valid in mixed 5-V/3.3-V designs where V_CC is supplied at 4.5 V or 5 V.

Is SN74CBT1G125DCKT pin-compatible with other SC-70 5-pin bus switches?

SN74CBT1G125DCKT follows the standard SC-70 5-pin pinout (OE, A, GND, V_CC, B), matching TI's own SN74LVC1G3157DCKR and ON Semiconductor's NL17SZ3157DBVT. However, functionally it is not interchangeable due to differences in r_on, ESD rating, and control logic (e.g., active-low OE vs. active-high EN). Always verify signal timing, voltage thresholds, and thermal behavior before substitution-even with identical pinouts.