Texas Instruments SN74CB3T3306DCUR

Overview

SN74CB3T3306DCUR from Texas Instruments is a dual 1-bit FET bus switch optimized for bidirectional level translation between 0–5 V signaling domains and 2.3–3.6 V logic supplies. It delivers 5 Ω typical ON-state resistance, <0.25 ns propagation delay at 3.3 V, and 5-V-tolerant I/Os with I_off partial-power-down protection-enabling safe interface between legacy 5-V peripherals and modern 3.3-V/2.5-V microcontrollers in USB host controllers.

For engineers reviewing the SN74CB3T3306DCUR datasheet, SN74CB3T3306DCUR pinout, SN74CB3T3306DCUR application, or SN74CB3T3306DCUR equivalent, key selection criteria include its 4.5 pF off-state I/O capacitance, active-low enable architecture, VCC-tracking output voltage translation, and compatibility with mixed-mode signal environments requiring simultaneous 5-V input and 2.5-V/3.3-V output operation.

Technical Context

The SN74CB3T3306DCUR implements two independent single-pole single-throw (SPST) FET switches, each controlled by an active-low OE input (1OE, 2OE). When enabled, the A–B path conducts bidirectionally with near-zero propagation delay governed by r_on–C_io time constant rather than gate drive timing.

Its level-shifting behavior arises from internal gate voltage generation (V_G ≈ V_CC + V_T), enabling 5-V signals to pass through while clamping outputs to V_CC. The device maintains high-impedance isolation during power-up/down via I_off circuitry that blocks backflow current when V_CC = 0 V.

Key Specifications

Pinout & Package

VSSOP-8 (DCU) package: 2.30 mm × 2.00 mm body, 0.5-mm lead pitch, 1.3-mm max height, RoHS-compliant NiPdAu/Sn lead finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBTD3306CDCTR and PCA9544APW, the SN74CB3T3306DCUR uniquely combines 5-V-tolerant I/Os, sub-0.3-ns delay, and VSSOP-8 footprint-making it the only option supporting direct TTL-level enable inputs and hot-pluggable 5-V peripheral interfacing without software overhead.

Availability

SN74CB3T3306DCUR is available at Aetrix Electronics and suitable for USB interface design, PCI bus isolation, memory interleaving, and low-power portable equipment requiring stable component supply across extended production lifecycles.

Supply support for SN74CB3T3306DCUR 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 delivering analog and embedded processing solutions, with over 90 years of innovation in precision analog, power management, and interface technologies.

The SN74CB3T3306DCUR belongs to TI's CB-series low-voltage bus switches, engineered specifically for mixed-signal interoperability in space-constrained, power-sensitive digital systems operating across multiple voltage domains.

FAQ

What is the maximum allowable input voltage on the I/O pins of the SN74CB3T3306DCUR?

The SN74CB3T3306DCUR supports 0 V to 5.5 V on all data I/O pins (1A, 1B, 2A, 2B) regardless of V_CC state-verified per absolute maximum ratings. This 5-V tolerance holds whether the device is powered (V_CC = 2.3–3.6 V) or fully unpowered (V_CC = 0 V), enabling safe hot-plug operation into live 5-V buses without external protection circuitry.

Does the SN74CB3T3306DCUR require external pull-up resistors on its enable inputs?

Yes-the SN74CB3T3306DCUR has active-low enables (1OE, 2OE), and TI recommends tying them to V_CC through a pull-up resistor during power-up to guarantee high-impedance state before control logic initializes. The minimum resistor value depends on the driver's sink capability; typical designs use 4.7 kΩ to 10 kΩ for 3.3-V systems.

Can the SN74CB3T3306DCUR translate 5-V inputs to 2.5-V outputs?

Yes-the SN74CB3T3306DCUR supports 5-V-to-2.5-V level shifting when V_CC = 2.5 V. Its V_CC-tracking architecture ensures output voltage follows the supply rail, so a 5-V input applied to 1A yields a 2.5-V output at 1B, verified in Figure 5 of the datasheet and confirmed under Recommended Operating Conditions for V_CC = 2.3–2.7 V.

What is the thermal performance of the SN74CB3T3306DCUR in its VSSOP-8 package?

The SN74CB3T3306DCUR in VSSOP-8 (DCU) has R_θJA = 209.4 °C/W and R_θJB = 88.9 °C/W. At 128 mA per channel and 5 Ω r_on, worst-case power dissipation is ~82 mW, resulting in <18 °C junction-to-ambient rise under standard JEDEC PCB conditions-well within the –40°C to 85°C operating range.

How does the SN74CB3T3306DCUR handle undershoot transients on its I/O lines?

The SN74CB3T3306DCUR integrates undershoot clamp diodes on all data and control pins, limiting negative excursions to –1.2 V (at –18 mA) as specified in Electrical Characteristics. This protects downstream CMOS inputs from damage due to transmission-line reflections or inductive kickback in high-speed routing scenarios.