Texas Instruments SN74CBT3125CRGYR

Overview

SN74CBT3125CRGYR from Texas Instruments is a quad 1-bit FET bus switch IC used for bidirectional signal gating in high-speed digital systems. It features 3 Ω typical ON-state resistance, near-zero propagation delay (0.15 ns at 5 V), undershoot protection to −2 V on A/B ports, and supports 0–5-V signaling across TTL/CMOS logic families. It enables low-distortion USB interface and bus isolation applications.

For engineers reviewing the SN74CBT3125CRGYR datasheet, SN74CBT3125CRGYR pinout, SN74CBT3125CRGYR application, or SN74CBT3125CRGYR equivalent, key selection criteria include Ioff partial-power-down capability, 5 pF OFF-state I/O capacitance, VCC range of 4–5.5 V, and RGY-packaged thermal performance (θJA = 47°C/W).

Technical Context

The SN74CBT3125CRGYR implements four independent single-pole single-throw (SPST) FET switches with separate OE control inputs (1OE–4OE). Each switch provides bidirectional conduction when its OE is low, and high-impedance isolation when OE is high - enabling flexible 1-bit or consolidated 4-bit bus routing.

Its active undershoot-protection circuitry monitors A/B port voltages and forces switch disable during −2 V transients, preventing false turn-on. The device uses Ioff to block backflow current during partial power-down, ensuring system-level isolation when VCC = 0 V.

Key Specifications

Pinout & Package

VQFN package (RGY), 14-pin, 3.5 mm × 3.5 mm, 0.5 mm pitch, exposed thermal pad. Pin 1 index located at top-left corner; thermal pad must be soldered for mechanical stability and thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3125CRGYR, SN74CBTD3384CDWR offers higher density but sacrifices undershoot protection and dual-voltage flexibility, while SN74LVC1G3157DCKR provides simpler control at the cost of isolation robustness and multi-bit integration.

Availability

SN74CBT3125CRGYR is available at Aetrix Electronics and suitable for USB interface isolation, memory bus segmentation, and industrial I/O multiplexing requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74CBT3125CRGYR 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 for industrial, automotive, and communications markets.

The SN74CBT3125CRGYR belongs to TI's CBT (Crossbar Bus Transceiver) family, designed specifically for high-speed, low-distortion signal gating in mixed-voltage digital systems with stringent transient immunity requirements.

FAQ

What is the maximum undershoot voltage the SN74CBT3125CRGYR can withstand on its A/B ports?

The SN74CBT3125CRGYR provides active undershoot protection up to −2 V on both A and B ports. This is achieved via internal clamping circuitry that forces the switch into the OFF state during transient negative excursions, preventing unintended conduction. The specification is verified per test conditions in the datasheet (VCC = 5.5 V, switch OFF, VIN = VCC or GND), and applies directly to the SN74CBT3125CRGYR in its RGY package.

Does the SN74CBT3125CRGYR support partial-power-down operation, and how is it implemented?

Yes, the SN74CBT3125CRGYR supports partial-power-down via its Ioff feature. When VCC = 0 V, the device limits backflow current to ≤10 µA, preventing damage to powered sections of the system. This behavior is inherent to the FET architecture and does not require external circuitry. The Ioff specification is guaranteed across the full operating temperature range (−40°C to 85°C) for the SN74CBT3125CRGYR.

What is the typical ON-state resistance of the SN74CBT3125CRGYR, and how does it vary with supply voltage?

The SN74CBT3125CRGYR has a typical ON-state resistance (ron) of 3 Ω at VCC = 4.5 V and IO = 30 mA. At VCC = 4 V, ron increases to 8–12 Ω; at VCC = 5 V, it decreases to 5–10 Ω. These values are measured between A and B terminals under specified current conditions and reflect the FET channel's voltage-dependent conductance - critical for predicting voltage drop in 5-V and 3.3-V data paths.

Can the SN74CBT3125CRGYR be used to interface 1.8-V logic with 5-V logic, and what design considerations apply?

Yes, the SN74CBT3125CRGYR supports 0–5-V signaling on its A/B I/O ports, making it suitable for level translation between 1.8-V and 5-V domains. No external biasing is required. However, OE inputs must be driven by TTL or 5-V/3.3-V CMOS levels (VIH ≥ 2 V, VIL ≤ 0.8 V), so 1.8-V controllers must use a level-shifter or buffer to drive OE. This constraint applies specifically to the SN74CBT3125CRGYR's control interface.

What is the thermal performance of the SN74CBT3125CRGYR in its RGY package, and how does it compare to other packages?

The SN74CBT3125CRGYR in the VQFN (RGY) package has a thermal impedance θJA of 47°C/W - significantly lower than SOIC (86°C/W), SSOP (90–96°C/W), or TSSOP (113°C/W) variants. This results from the exposed thermal pad and compact 3.5 mm × 3.5 mm footprint. Proper soldering of the thermal pad to a PCB copper plane is mandatory to achieve this rating, as specified in TI's SLUA271 application note for the SN74CBT3125CRGYR.