Texas Instruments SN74CBT3305CD

Overview

SN74CBT3305CD from Texas Instruments is a dual 1-bit FET bus switch in SOIC-8 package, featuring 3 Ω typical ON-state resistance (ron), –2 V undershoot protection on A/B ports, and 4 V to 5.5 V VCC operation. It enables bidirectional signal gating in USB interfaces and low-distortion analog/digital bus isolation with near-zero propagation delay (0.24 ns typical).

For engineers reviewing the SN74CBT3305CD datasheet, SN74CBT3305CD pinout, SN74CBT3305CD application, or SN74CBT3305CD equivalent, key selection criteria include Ioff partial-power-down support, 5 pF typical OFF-state I/O capacitance, TTL/CMOS-compatible control inputs, and –2 V undershoot clamping for robust signal integrity in mixed-voltage systems.

Technical Context

The SN74CBT3305CD implements two independent FET-based transmission gates, each controlled by dedicated OE inputs (1OE, 2OE), enabling flexible 1-bit or combined 2-bit switching. Its active undershoot-protection circuitry monitors A/B port voltages and forces OFF-state isolation when undershoot events below –2 V occur.

Each switch supports 0–5 V signaling across all logic families (0.8 V to 5 V), operates with 3 µA max ICC, and maintains high-impedance isolation during power-down via Ioff functionality-preventing backflow current when VCC = 0 V and VI/O = 0–5.5 V.

Key Specifications

Pinout & Package

SN74CBT3305CD is housed in an 8-pin SOIC (D) package, 3.91 mm wide, 4.9 mm long, and 1.75 mm maximum height, with standard JEDEC MS-012 footprint and RoHS-compliant NiPdAu lead finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3305CD, SN74CBTD3305CD trades undershoot protection and 5 V compatibility for lower voltage operation, while 74LVC1G3157DCKR sacrifices channel count, Ioff, and transient resilience to reduce footprint-making SN74CBT3305CD the sole option meeting full USB interface, hot-swap, and mixed-voltage isolation requirements.

Availability

SN74CBT3305CD is available at Aetrix Electronics and suitable for USB interface design, industrial bus isolation, and analog multiplexing requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.

Supply support for SN74CBT3305CD 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 with emphasis on reliability, precision, and power efficiency.

The SN74CBT3305CD belongs to TI's CBT (Crossbar Bus Transceiver) family, engineered for high-speed, low-distortion signal routing in mixed-voltage digital and analog systems where signal integrity and power-domain independence are critical.

FAQ

What is the maximum undershoot voltage the SN74CBT3305CD can tolerate on its A and B ports?

The SN74CBT3305CD provides active undershoot protection up to –2 V on both A and B ports, verified per test conditions in the SCDS125B datasheet. This ensures the switch remains reliably OFF during transient negative excursions, preventing unintended conduction or latch-up. The SN74CBT3305CD achieves this via integrated clamp circuitry that senses undershoot and disables the FET path without external components.

Does the SN74CBT3305CD support partial-power-down operation, and how is it implemented?

Yes, the SN74CBT3305CD fully supports partial-power-down via its Ioff feature, which limits leakage to 10 µA max when VCC = 0 V and VI/O = 0–5.5 V. This prevents damaging backflow current from live I/O lines into a powered-down system domain. The SN74CBT3305CD achieves this through internal transistor biasing that isolates the switch channel when supply is removed, making it suitable for hot-swap and modular power architectures.

Can the SN74CBT3305CD be used for analog signal switching, and what parameters validate that capability?

Yes, the SN74CBT3305CD is qualified for analog signal switching due to its 3 Ω typical ron, 5 pF Cio(OFF), and flat frequency response up to 100 MHz. Its bidirectional, voltage-agnostic I/O (0–5.5 V) and low charge injection (<1 pC) preserve signal fidelity in sensor and audio paths. These characteristics are measured and specified in the SN74CBT3305CD electrical characteristics table, confirming suitability beyond digital bus isolation.

What is the recommended practice for OE pin handling during power-up and power-down sequences?

To ensure high-impedance state during power transitions, OE pins (1OE and 2OE) of the SN74CBT3305CD should be tied to GND via a pulldown resistor. TI specifies minimum resistor value based on driver sink capability; typical values range from 1 kΩ to 10 kΩ. This prevents floating OE states that could cause momentary ON conduction or increased ICC. The SN74CBT3305CD datasheet explicitly recommends this for robust power sequencing.

How does the SN74CBT3305CD compare to standard CMOS analog switches in terms of propagation delay and ON-resistance?

The SN74CBT3305CD delivers 0.24 ns typical propagation delay and 3 Ω typical ON-resistance-significantly lower than general-purpose CMOS analog switches (e.g., 10–50 ns tpd, 50–500 Ω ron). This performance stems from its optimized FET bus-switch architecture, not generic transmission-gate design. These values are measured and guaranteed across temperature and voltage in the SN74CBT3305CD datasheet, enabling precise timing-critical applications like USB signal gating.