Texas Instruments SN74CB3Q3305DCUR

Overview

SN74CB3Q3305 from Texas Instruments is a dual 1-bit FET bus switch optimized for high-bandwidth, level-shifting signal routing in 2.5-V/3.3-V systems. It delivers bidirectional data flow with near-zero propagation delay (0.15 ns typical), 3 Ω typical ON-state resistance, and 5-V-tolerant I/Os - enabling interoperability between 5-V peripherals and lower-voltage controllers in optical networking and USB interfaces.

For engineers reviewing the SN74CB3Q3305 datasheet, SN74CB3Q3305 pinout, SN74CB3Q3305 application, or SN74CB3Q3305 equivalent, key selection criteria include its 500 MHz bandwidth capability, I_OFF-enabled partial-power-down isolation, flat r_ON over voltage/temperature, 3.5 pF OFF-state I/O capacitance, and VSSOP-8 package compatibility with space-constrained PCB layouts.

Technical Context

The SN74CB3Q3305 integrates two independent 1-bit switches, each controlled by dedicated OE inputs (1OE, 2OE), supporting either dual 1-bit or single 2-bit bus switching configurations. Its charge-pump architecture elevates the gate voltage of the pass FETs to maintain low and flat r_ON across the full 2.3–3.6 V V_CC range and operating temperature (–40°C to +85°C).

Each channel supports 0–5 V signal switching at 3.3 V V_CC or 0–3.3 V at 2.5 V V_CC, with 5-V-tolerant I/Os functional during power-up, operation, and power-down states. The device implements I_OFF circuitry to block backflow current when V_CC = 0 V, ensuring robust isolation and system-level fault tolerance.

Key Specifications

Pinout & Package

VSSOP-8 (DCU) package: 2.00 mm × 3.10 mm body size, 0.5-mm lead pitch, surface-mount, RoHS-compliant, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CB3Q3305, SN74CBT3305CPW trades 5-V tolerance and I_OFF for lower cost, while TS3A24159DGSR extends low-voltage support but sacrifices bandwidth and I/O voltage range - making SN74CB3Q3305 the sole option for 500 MHz, 5-V-tolerant, partial-power-down bus switching in VSSOP-8.

Availability

SN74CB3Q3305 is available at Aetrix Electronics and suitable for optical networking, USB 2.0 isolation, and IP phone baseband routing requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant VSSOP packaging.

Supply support for SN74CB3Q3305 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 decades of expertise in high-speed interface solutions.

The SN74CB3Q3305 belongs to TI's CB3Q family of high-bandwidth FET bus switches, designed specifically for broadband communications, optical transport, and data-intensive computing systems demanding low-latency, level-shifting signal routing.

FAQ

What is the maximum signal frequency supported by the SN74CB3Q3305?

The SN74CB3Q3305 supports signal frequencies up to 500 MHz, verified under load conditions with typical r_ON and C_IO(OFF). This bandwidth is enabled by its charge-pump architecture and low 3.5 pF OFF-state capacitance, making SN74CB3Q3305 suitable for USB 2.0, EPON, and high-speed serial interconnects without signal degradation.

Does the SN74CB3Q3305 support level shifting between 5-V and 3.3-V logic domains?

Yes, the SN74CB3Q3305 supports bidirectional level shifting: it accepts 0–5 V signals on its I/O ports while operating from a 3.3-V V_CC, and also supports 0–3.3 V signaling at 2.5-V V_CC. This 5-V tolerance applies whether the device is powered up, powered down, or in transition - a key capability confirmed in the absolute maximum ratings and functional description of SN74CB3Q3305.

How does the I_OFF feature protect the SN74CB3Q3305 during partial power-down?

The I_OFF circuitry in SN74CB3Q3305 actively disables current paths when V_CC = 0 V, limiting backflow current to just 1 µA. This prevents damage to powered-down sections and ensures isolation between live and unpowered subsystems - a requirement validated per JESD78 Class II latch-up testing and explicitly documented in the SN74CB3Q3305 electrical characteristics table.

What is the recommended bypass capacitor for the SN74CB3Q3305 V_CC pin?

A 0.1 µF ceramic capacitor placed as close as possible to the V_CC pin is mandatory for stable operation of SN74CB3Q3305. This value is specified in Section 10 of the datasheet to suppress high-frequency noise and supply ripple, especially critical given the device's 20 MHz OE switching capability and 500 MHz signal path - failure to implement this degrades SN74CB3Q3305 bandwidth and increases jitter.

Can the SN74CB3Q3305 be used in a single 2-bit bus switch configuration?

Yes, the SN74CB3Q3305 can operate as a single 2-bit bus switch by tying 1OE and 2OE together and using 1A/1B and 2A/2B as the two data lanes. Its functional block diagram and truth table confirm independent or synchronized control modes, and the dual-channel architecture of SN74CB3Q3305 makes it ideal for compact 2-bit multiplexing in space-constrained optical module designs.