Texas Instruments SN74CB3Q3305PWRG4

Overview

SN74CB3Q3305 from Texas Instruments is a dual 1-bit FET bus switch optimized for high-bandwidth, level-translating signal routing in mixed-voltage systems. It supports bidirectional 0–5 V signaling with 3.3 V V_CC, delivers 3 Ω typical ON-state resistance, <0.15 ns propagation delay, and 500 MHz bandwidth - enabling use in USB interfaces, optical networking backplanes, and broadband communications equipment.

For engineers reviewing the SN74CB3Q3305 datasheet, SN74CB3Q3305 pinout, SN74CB3Q3305 application, or SN74CB3Q3305 equivalent, key selection considerations include 5-V-tolerant I/O under powered-up/down conditions, I_off-enabled partial-power-down isolation, low 3.5 pF OFF-state capacitance, and TSSOP-8 package compatibility with high-speed layout requirements.

Technical Context

The SN74CB3Q3305 integrates two independent FET switches, each controlled by dedicated OE inputs (1OE, 2OE), enabling selective channel isolation. Its charge-pump gate drive maintains flat r_on (3–8 Ω) across 2.3–3.6 V V_CC and –40°C to 85°C, supporting voltage-agnostic signal pass-through without directionality constraints.

Each switch exhibits near-zero propagation delay due to low r_on–C_io product (3 Ω × 3.5 pF), while I_off circuitry blocks reverse current flow during power-down, ensuring system-level robustness in hot-swap and multi-rail environments.

Key Specifications

Pinout & Package

SN74CB3Q3305 is packaged in an 8-pin TSSOP (PW) with 3.00 mm × 6.10 mm body size, lead-free (NIPDAU) finish, and moisture sensitivity level 1 (260°C peak reflow).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBTLV3305PWR and TS3A24159RGTR, the SN74CB3Q3305 uniquely combines 5-V I/O tolerance with charge-pump-stabilized r_on and I_off-enabled isolation - making it the only option among the three suitable for mixed-rail infrastructure equipment requiring hot-swap resilience and wide voltage interoperability.

Availability

SN74CB3Q3305 is available at Aetrix Electronics and suitable for optical networking backplanes, USB 2.0 interface isolation, and WiMAX baseband multiplexing requiring stable component supply across extended production lifecycles.

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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.

The SN74CB3Q3305 belongs to TI's CB3Q family of high-bandwidth FET bus switches, engineered specifically for voltage-flexible, low-distortion signal routing in broadband infrastructure and data-intensive computing systems.

FAQ

What is the maximum signal frequency supported by the SN74CB3Q3305?

The SN74CB3Q3305 supports a maximum signal bandwidth of 500 MHz, verified under typical operating conditions (V_CC = 3.3 V, T_A = 25°C). This rating assumes optimal PCB layout - including controlled-impedance traces, minimized stub lengths, and proper grounding - as parasitic capacitance and inductance directly impact achievable frequency performance. The SN74CB3Q3305 achieves this via low 3.5 pF OFF-state capacitance and 3 Ω typical ON-resistance.

Does the SN74CB3Q3305 support level translation between 1.8-V and 5-V logic domains?

Yes, the SN74CB3Q3305 supports bidirectional level translation between 1.8-V and 5-V domains when powered from 2.5 V or 3.3 V. With V_CC = 2.5 V, it accepts 0–3.3 V on I/O ports; with V_CC = 3.3 V, it handles 0–5 V. Its 5-V-tolerant I/O structure and charge-pump gate drive ensure consistent r_on and signal fidelity across these combinations - confirmed in TI's SCDS141D datasheet Section 8.3.

How does the SN74CB3Q3305 behave during power-down sequences?

During power-down, the SN74CB3Q3305 enters a high-impedance state with I_off ≤ 1 µA, preventing back-current flow from live I/O lines into the unpowered device. This I_off feature - specified in Section 6.5 of the SN74CB3Q3305 datasheet - ensures safe partial-power-down operation in multi-rail systems, such as optical line cards where digital and analog sections power up/down independently.

Can the SN74CB3Q3305 replace mechanical relays in signal routing applications?

The SN74CB3Q3305 is not a relay replacement but a solid-state alternative for low-voltage, high-speed signal routing - offering nanosecond switching, no contact wear, and integration advantages. Unlike relays, it cannot handle high voltages (>5.5 V) or high currents (>±64 mA per channel). Its value lies in replacing discrete MOSFET-based switches or older TTL bus switches in applications like USB, PCIe Gen1, and SFP+ where speed, size, and reliability outweigh high-power handling needs.

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

Texas Instruments specifies a 0.1 µF ceramic capacitor placed as close as possible to the V_CC pin of the SN74CB3Q3305, with short, low-inductance traces to GND. This is required to suppress high-frequency noise generated by fast switching transitions and maintain stable charge-pump operation. Layout guidance in Section 11 of the SN74CB3Q3305 datasheet emphasizes minimizing loop area to preserve signal integrity at 500 MHz.