Texas Instruments SN74CBT3345CPWR

Overview

SN74CBT3345CPWR from Texas Instruments is an 8-bit bidirectional FET bus switch IC with dual OE control, 3 Ω typical ON-state resistance, near-zero propagation delay (0.15 ns at 5 V), and undershoot protection up to −2 V on A/B ports. It enables voltage-level agnostic signal gating in USB interfaces and memory interleaving applications.

For engineers reviewing the SN74CBT3345CPWR datasheet, SN74CBT3345CPWR pinout, SN74CBT3345CPWR application, or SN74CBT3345CPWR equivalent, key selection criteria include Ioff partial-power-down support, 0–5-V data I/O compatibility, dual active-high/active-low enable logic, and TSSOP-20 thermal performance (θJA = 83°C/W).

Technical Context

The SN74CBT3345CPWR implements eight independent transmission-gate switches controlled by complementary OE inputs: OE high *or* OE low enables bidirectional conduction between A1–A8 and B1–B8; both OE low and OE high forces high-impedance isolation. Its FET-based architecture eliminates DC path current and supports rail-to-rail analog/digital signal pass-through.

Undershoot protection circuitry actively clamps A/B port voltages down to −2 V during off-isolation, preventing false turn-on and latch-up. The device meets JESD 78 Class II latch-up immunity (>100 mA) and JESD 22 ESD ratings (2000-V HBM, 1000-V CDM), enabling robust operation in hot-plug and mixed-voltage systems.

Key Specifications

Pinout & Package

TSSOP-20 package (PW), 6.95 mm × 4.4 mm × 1.2 mm height, 0.65 mm pitch, 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 SN74CBT3345CPWR, SN74CBTD3305PWR trades undershoot resilience for higher density, while TS3A24159RGTR sacrifices channel count and Ioff for lower resistance and footprint - neither offers identical 8-bit + dual-OE + −2 V protection + Ioff combination.

Availability

SN74CBT3345CPWR is available at Aetrix Electronics and suitable for USB interface design, memory interleaving systems, and industrial bus isolation requiring stable component supply and long-term manufacturability.

Supply support for SN74CBT3345CPWR 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 over 90 years of innovation in high-reliability components.

The SN74CBT3345CPWR belongs to TI's CBT (Crosspoint Bus Transceiver) family, engineered for high-speed, low-distortion signal routing in mixed-voltage digital systems where timing precision and power-state robustness are critical.

FAQ

What is the maximum allowable undershoot voltage at the A/B ports of the SN74CBT3345CPWR?

The SN74CBT3345CPWR provides active undershoot protection up to −2 V on both A and B ports when the switch is in the OFF state. This is verified per the absolute maximum rating VI/O = −0.5 V to 7 V and confirmed in the undershoot characteristics table (VOUTU min = 2 V, VOH−0.3 V). Operation below −2 V risks violating the −0.5 V absolute minimum and may damage internal clamp structures. The SN74CBT3345CPWR must not be exposed to sustained voltages less than −0.5 V.

Does the SN74CBT3345CPWR support partial-power-down mode, and how is it implemented?

Yes, the SN74CBT3345CPWR supports partial-power-down mode via its Ioff feature. When VCC = 0 V, the device limits back-current to ≤10 µA even if A/B ports are biased at up to 5.5 V. This is achieved through internal transistor cutoff and isolation circuitry, ensuring no damaging current flows into the unpowered VCC rail. The SN74CBT3345CPWR maintains high-impedance isolation during this condition, making it suitable for systems with staggered power sequencing.

What are the recommended pull-up/pull-down resistors for OE and OE pins during power-up of the SN74CBT3345CPWR?

TI recommends tying OE to VCC through a pull-up resistor and OE to GND through a pulldown resistor to guarantee high-impedance state at power-up. Minimum resistor values depend on driver strength: for standard CMOS drivers, 10 kΩ is typical. The SN74CBT3345CPWR datasheet specifies that OE should be pulled to VCC and OE to GND to avoid undefined states during VCC ramp. These resistors ensure the switch remains OFF until firmware asserts valid enable logic, preventing bus contention during boot.

Can the SN74CBT3345CPWR be used to switch analog signals, and what is its bandwidth limitation?

Yes, the SN74CBT3345CPWR is specified for both digital and analog applications due to its low ron (3 Ω typ), flat on-resistance vs. voltage curve, and rail-to-rail 0–5.5 V I/O capability. Bandwidth is limited by the RC time constant formed by ron and load capacitance: with 5.5 pF Cio(OFF) and 3 Ω ron, the −3 dB point exceeds 10 GHz. Real-world analog bandwidth is governed by PCB layout and external load; for audio or sensor signals (<200 kHz), the SN74CBT3345CPWR introduces negligible distortion or attenuation.

What is the thermal resistance (θJA) of the SN74CBT3345CPWR in its TSSOP-20 package?

According to the TI datasheet SCDS129A, the SN74CBT3345CPWR in the PW (TSSOP-20) package has a junction-to-ambient thermal resistance (θJA) of 83°C/W under standard JEDEC test conditions (JESD 51-7). This value assumes a 2-layer board with 1-in² copper pad. Actual θJA in end equipment depends on PCB copper area, airflow, and nearby heat sources. The SN74CBT3345CPWR's low ICC (3 µA max) minimizes self-heating, making thermal derating rarely necessary in typical applications.