Texas Instruments SN74CBTD3305CD

Overview

SN74CBTD3305CD from Texas Instruments is a dual 1-bit FET bus switch IC with integrated level shifting and −2-V undershoot protection, operating from 4.5 V to 5.5 V VCC. It enables bidirectional 5-V-to-3.3-V signal translation, features 3 Ω typical ON-state resistance, 5 pF OFF-state I/O capacitance, and supports 0–5-V signaling across 0.8-V to 5-V logic families. It is used in USB interface isolation and memory interleaving where low-distortion, near-zero-delay signal gating is required.

For engineers reviewing the SN74CBTD3305CD datasheet, SN74CBTD3305CD pinout, SN74CBTD3305CD application, or SN74CBTD3305CD equivalent, key selection criteria include its dual independent OE control, −2-V undershoot tolerance on A/B ports, Ioff partial-power-down support, 0.15 ns propagation delay, and SOIC-8 package compatibility with industrial temperature range (−40°C to 85°C).

Technical Context

This device implements two independent TTL-compatible FET transmission gates, each with separate output-enable (1OE/2OE) inputs and active undershoot-protection circuitry that clamps A/B port voltages down to −2 V while maintaining OFF-state isolation. The integrated series diode between VCC and input enables 5-V-to-3.3-V level shifting without external components.

It operates in partial-power-down mode via Ioff, preventing backflow current when VCC = 0 V, and maintains high-impedance isolation between A and B ports during power-up/down when OE is pulled low. Control inputs accept TTL or 5-V/3.3-V CMOS logic levels, and data I/Os tolerate 0–5.5-V signals regardless of VCC state.

Key Specifications

Pinout & Package

SN74CBTD3305CD is housed in an 8-pin SOIC (D) package, 3.94 mm wide × 4.9 mm long × 1.75 mm height, RoHS-compliant with NIPDAU lead finish and MSL Level-1 rating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBTD3305CD, SN74CBT3244D offers higher channel density but requires external level shifters and lacks undershoot hardening, while SN74LVC1G3157DCKR sacrifices robustness and voltage flexibility for smaller footprint and lower static current - making SN74CBTD3305CD optimal for mixed-voltage, high-reliability digital gating.

Availability

SN74CBTD3305CD is available at Aetrix Electronics and suitable for USB interface isolation, memory interleaving, bus isolation, and low-distortion signal gating requiring stable component supply, full traceability, and long-term industrial lifecycle support.

Supply support for SN74CBTD3305CD 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 logic solutions, with decades of expertise in high-speed interface and power management ICs.

The SN74CBTD3305CD belongs to TI's 74CBT family of advanced bus switches, engineered specifically for robust, low-latency signal routing in mixed-voltage digital systems with stringent ESD and undershoot requirements.

FAQ

What is the maximum undershoot voltage the SN74CBTD3305CD can withstand on its A and B ports?

The SN74CBTD3305CD provides active undershoot protection up to −2 V on both A and B ports when the switch is in the OFF state. This is achieved through internal sensing circuitry that maintains isolation during negative transients, preventing false turn-on or latch-up. The specification is validated per test conditions in the datasheet (VCC = 5.5 V, switch OFF), and applies directly to the SN74CBTD3305CD under recommended operating conditions.

Does the SN74CBTD3305CD support level shifting from 3.3-V inputs to 5-V outputs?

No, the SN74CBTD3305CD supports only 5-V-to-3.3-V level shifting via its integrated series diode between VCC and the input path. It does not provide upward translation. When a 3.3-V signal is applied to the A or B port, the output reflects that voltage bidirectionally without boosting. The SN74CBTD3305CD is designed for downward translation only, and its VI/O range (0–5.5 V) ensures compatibility with 3.3-V logic driving into a 5-V system, but no voltage gain occurs.

Can the SN74CBTD3305CD be used in partial-power-down mode, and how is it implemented?

Yes, the SN74CBTD3305CD supports partial-power-down mode via its Ioff feature. When VCC = 0 V, the device limits OFF-state current to ≤10 μA, blocking reverse current flow from live I/O lines into the unpowered VCC rail. This behavior is intrinsic to the FET architecture and requires no external circuitry. For reliable operation, OE pins should be tied to GND through a pulldown resistor during power transitions to ensure high-impedance states - a requirement confirmed in the SN74CBTD3305CD datasheet's power-up/down guidance.

What is the typical ON-state resistance (ron) of the SN74CBTD3305CD, and how does it affect signal integrity?

The SN74CBTD3305CD has a typical ON-state resistance of 3 Ω at VCC = 4.5 V, measured between A and B terminals under 30 mA current. This low ron minimizes voltage drop (<90 mV at 30 mA) and power dissipation (<2.7 mW), preserving signal amplitude and reducing jitter in high-speed digital paths. Combined with 5 pF OFF-state capacitance, this enables clean edge transitions and minimal inter-symbol interference - critical for SN74CBTD3305CD deployments in USB and memory bus applications.

Is the SN74CBTD3305CD pin-compatible with other devices in the 74CBT family, such as the SN74CBTD3306?

No, the SN74CBTD3305CD is not pin-compatible with the SN74CBTD3306. While both are dual bus switches in SOIC-8 packages, the SN74CBTD3306 uses inverted OE logic (active-low) and different pin assignments: its 1OE and 2OE are on pins 1 and 4, whereas SN74CBTD3305CD places them on pins 1 and 6. The pinout mismatch means direct replacement would require PCB redesign. Always verify pin mapping using the official SN74CBTD3305CD and SN74CBTD3306 datasheets before substitution.