Texas Instruments SN74CBTD3861DWG4

Overview

SN74CBTD3861DWG4 from Texas Instruments is a 10-bit FET bus switch with integrated level-shifting capability, designed for bidirectional 5-V-to-3.3-V signal translation in high-speed digital systems. It features 5-Ω on-state resistance, TTL-compatible inputs, and a single OE control enabling/disabling all ten channels simultaneously. Used in mixed-voltage memory and data bus interfaces where minimal propagation delay (<0.35 ns) and low channel crosstalk are critical.

For engineers reviewing the SN74CBTD3861DWG4 datasheet, SN74CBTD3861DWG4 pinout, SN74CBTD3861DWG4 application, or SN74CBTD3861DWG4 equivalent, key selection criteria include verified 5-Ω r_on, guaranteed 4.5–5.5 V supply operation, OE-controlled high-impedance isolation, and TSSOP-24 package compatibility with 0.65-mm pitch PCB layouts.

Technical Context

This device implements a monolithic 10-channel analog switch using NMOS FETs with integrated input diodes to V_CC, enabling passive level shifting from 5-V inputs to 3.3-V outputs without external components. The OE input controls all channels synchronously in positive logic: low enables conduction, high forces high-impedance isolation between A and B ports.

It operates strictly within 4.5–5.5 V supply range and supports continuous channel current up to 128 mA per switch. Input clamp current rating (–50 mA) and absolute max V_I of –0.5 V to 7 V ensure robustness against transient overvoltage during hot-swap or bus contention events.

Key Specifications

Pinout & Package

TSSOP-24 package (PW), 7.9 mm × 4.5 mm × 1.2 mm body, 0.65 mm lead pitch, exposed pad not present, RoHS-compliant NiPdAu finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBTD3861DWG4, SN74CBT3861PW offers identical performance in tube format, while SN74LVC4245APWR provides dual-rail flexibility at the cost of added complexity, reduced speed, and higher capacitance - making it unsuitable for high-frequency bus isolation tasks.

Availability

SN74CBTD3861DWG4 is available at Aetrix Electronics and suitable for memory subsystems, industrial backplanes, FPGA I/O bridging, and legacy bus upgrades requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74CBTD3861DWG4 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 U.S.-based semiconductor company specializing in analog, embedded processing, and logic solutions with broad industrial and automotive qualification coverage.

The SN74CBTD3861DWG4 belongs to TI's 74CBT family of high-speed CMOS bus switches, engineered specifically for low-latency, low-power voltage translation in mixed-signal computing and communications infrastructure.

FAQ

What is the maximum continuous current rating per channel for the SN74CBTD3861DWG4?

The SN74CBTD3861DWG4 supports a continuous channel current of 128 mA per switch. This rating is specified under recommended operating conditions (V_CC = 4.5 V to 5.5 V) and ensures reliable conduction without thermal runaway or parametric shift. Exceeding this value risks permanent damage to the internal FET structure, especially under sustained load or elevated ambient temperature.

Does the SN74CBTD3861DWG4 require external pull-up or pull-down resistors on the OE pin?

No, the SN74CBTD3861DWG4 does not require external pull-up or pull-down resistors on the OE pin - but unused OE must be actively driven to V_CC or GND. TI's SCBA004 application report specifies that floating OE inputs cause undefined switching behavior and increased ICC. The SN74CBTD3861DWG4's OE input has TTL-compatible thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2 V), so direct connection to a microcontroller GPIO or fixed rail satisfies this requirement.

Can the SN74CBTD3861DWG4 translate signals from 3.3 V to 5 V?

No, the SN74CBTD3861DWG4 is designed exclusively for 5-V-to-3.3-V level shifting via its internal diode-to-V_CC architecture. Driving 3.3-V signals into port A will not produce 5-V outputs at port B because the diode only conducts toward V_CC. Attempting reverse translation results in degraded VOL, increased propagation delay, and potential latch-up risk. For bidirectional translation, a dedicated dual-supply translator like SN74LVC4245A is required.

What is the thermal impedance (θ_JA) of the SN74CBTD3861DWG4 in its TSSOP-24 package?

The SN74CBTD3861DWG4 in the PW (TSSOP-24) package has a specified junction-to-ambient thermal impedance (θ_JA) of 88°C/W under JEDEC JESD51-7 conditions. This value assumes a standard 2-layer board with 1-in² copper pour. Actual thermal performance improves significantly with internal layer copper planes and thermal vias - design guidelines recommend ≥4 thermal vias under the package body to reduce θ_JA by ~25%.

Is the SN74CBTD3861DWG4 pin-compatible with other packages in the same family?

Yes, the SN74CBTD3861DWG4 shares identical pinout and functionality with all 24-pin variants in the SN74CBTD3861 family, including DW (SOIC), DB (SSOP), DBQ (QSOP), DGV (TVSOP), and PW (TSSOP). All variants use the same top-view pin mapping: A1–A10 on left side, B1–B10 on right side, OE at pin 23, V_CC at pin 12, GND at pin 11, and NC at pins 1 and 24. Mechanical dimensions differ, but PCB footprint must be adapted per package drawing.