Texas Instruments SN74CBT3345PW

Overview

SN74CBT3345PW from Texas Instruments is an 8-bit high-speed TTL-compatible bus switch with dual output-enable control, 5-Ω on-state resistance, 0.25 ns propagation delay, and standard '245 pinout - used for low-latency bidirectional data routing in industrial control backplanes and legacy parallel bus interfaces.

For engineers reviewing the SN74CBT3345PW datasheet, SN74CBT3345PW pinout, SN74CBT3345PW application, or SN74CBT3345PW equivalent, key selection criteria include its dual OE logic configuration, 4.5–5.5 V supply range, −40°C to 85°C operating temperature, TSSOP-20 package, and 128 mA continuous channel current rating.

Technical Context

The SN74CBT3345PW implements a single 8-bit bidirectional analog switch bank using NMOS pass-transistor architecture, enabling low-resistance signal paths between port A (pins 1–8) and port B (pins 13–20). Its dual OE inputs operate with active-low and active-high polarity, allowing flexible enable/disable sequencing without external logic inversion.

Switching is controlled by complementary OE signals: the switch conducts when OE is low OR OE is high; it enters high-impedance isolation when OE is high AND OE is low. This architecture supports hot-swap-capable bus arbitration and dynamic bus segmentation in multi-master systems.

Key Specifications

Pinout & Package

TSSOP-20 package (PW), 6.5 mm × 4.4 mm body, 1.2 mm max height, 0.65 mm lead pitch, exposed pad not present, JEDEC MO-153 compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3345PW, SN74CBTD3345PW adds bus-hold functionality at minor power cost but retains identical pinout and switching performance, while SN74LVC245APW offers voltage translation capability but sacrifices bidirectionality and speed - making SN74CBT3345PW optimal for 5-V, low-latency, bidirectional bus isolation.

Availability

SN74CBT3345PW is available at Aetrix Electronics and suitable for industrial backplane interfacing, legacy parallel peripheral expansion, hot-swappable module arbitration, and multi-master bus segmentation requiring stable component supply across extended product lifecycles.

Supply support for SN74CBT3345PW 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 company headquartered in Dallas, Texas, delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and consumer markets.

The SN74CBT3345PW belongs to TI's CBT (CrossBar Technology) family of high-speed bus switches, designed specifically for low-latency, bidirectional signal routing in 5-V legacy computing and industrial control systems.

FAQ

What is the function of the dual OE inputs on the SN74CBT3345PW?

The SN74CBT3345PW features two complementary output-enable inputs: OE (active-low, Pin 1) and OE (active-high, Pin 19). The switch conducts between port A and port B when either OE is low OR OE is high. It enters high-impedance isolation only when OE is high AND OE is low. This dual-control scheme allows flexible integration with existing enable logic without requiring external inverters, simplifying system-level timing and reducing component count in bus arbitration circuits.

Does the SN74CBT3345PW support 3.3-V logic levels?

The SN74CBT3345PW is specified for 4.5–5.5 V operation and features TTL-compatible input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V), making it compatible with 3.3-V CMOS outputs driving into its inputs - provided the 3.3-V device can tolerate 5-V-tolerant inputs. However, its VCC must be 5 V, so it cannot be powered from 3.3 V. For native 3.3-V operation, consider the SN74LVC245A series instead.

What is the maximum capacitive load the SN74CBT3345PW can drive while maintaining specified timing?

The SN74CBT3345PW's switching characteristics - including 0.25 ns propagation delay (tpd) and 9.1 ns enable time (ten) - are characterized at CL = 50 pF. Driving loads significantly exceeding 50 pF increases RC delay and degrades timing margins. For reliable operation beyond 50 pF, derating analysis is required; TI recommends limiting total node capacitance (including trace, stub, and load) to ≤60 pF to maintain sub-nanosecond performance in high-speed parallel bus applications using the SN74CBT3345PW.

Is the SN74CBT3345PW pin-compatible with other packages in the same family?

Yes - the SN74CBT3345PW (TSSOP-20), SN74CBT3345DW (SOIC-20), and SN74CBT3345DBR (SSOP-20) share identical pin numbering, signal assignment, and electrical specifications. All variants use the standard '245-type pinout: OE (Pin 1), A1–A8 (Pins 2–9), GND (Pin 10), VCC (Pin 11), OE (Pin 19), and B1–B8 (Pins 13–20). This allows direct mechanical and functional substitution across packages based on board space and thermal requirements, without layout or firmware changes.

What is the thermal performance of the SN74CBT3345PW in its TSSOP package?

The SN74CBT3345PW in the TSSOP-20 (PW) package has a junction-to-ambient thermal impedance (θJA) of 83°C/W, as specified in the absolute maximum ratings table. At full 128 mA channel current per switch and worst-case 5.5 V supply, power dissipation remains below 100 mW - resulting in a junction temperature rise of <8.3°C above ambient. This ensures stable operation within the −40°C to 85°C industrial temperature range without heatsinking, provided the PCB provides adequate copper pour and airflow per TI's recommended layout guidelines for PW package.