Texas Instruments SN74CBT3245AGQNR

Overview

SN74CBT3245AGQNR from Texas Instruments is an octal FET bus switch IC designed for high-speed TTL-compatible bidirectional signal routing between two 8-bit ports (A and B). It features 5-Ω typical on-state resistance, 0.25 ns propagation delay at 5 V, and operates from −40°C to 85°C with supply voltage range 4 V to 5.5 V. It is used in memory address/data bus isolation and hot-swap interface control.

For engineers reviewing the SN74CBT3245AGQNR datasheet, SN74CBT3245AGQNR pinout, SN74CBT3245AGQNR application, or SN74CBT3245AGQNR equivalent, key selection criteria include low on-resistance for minimal signal degradation, fast enable/disable timing (1.9 ns ten / 2.1 ns tdis), TTL-compatible control inputs, VFBGA package footprint compatibility, and high-impedance isolation during power sequencing.

Technical Context

The SN74CBT3245AGQNR implements eight independent bilateral analog switches controlled by a single active-low output-enable (OE) input. When OE is low, A1–A8 are electrically connected to B1–B8 with near-zero DC offset and minimal RC delay; when OE is high, both ports present >10⁹ Ω isolation.

Its FET-based architecture eliminates DC path current and supports rail-to-rail analog/digital signal switching up to 5.5 V. The device requires no external biasing and uses standard '245-type pinout mapping - critical for drop-in replacement in legacy SOIC/SSOP designs while enabling space-constrained layouts via its 3.5 mm × 4.5 mm VFBGA (GQN) package.

Key Specifications

Pinout & Package

VFBGA-20 (GQN) package: 3.5 mm × 4.5 mm, 0.5 mm pitch, 21-terminal layout including 20 signal/Power/Ground pins and 1 exposed thermal pad (pin 21). Pin 1 marked by corner chamfer; top-side marking "CU245A".

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3245AGQNR, the TSSOP (PWR) variant offers easier handling and soldering at the expense of 2.5× larger area, while the SSOP (DBQR) delivers superior thermal performance in established layouts but demands tighter PCB fabrication tolerances.

Availability

SN74CBT3245AGQNR is available at Aetrix Electronics and suitable for industrial automation interfaces, telecom backplane interconnects, and embedded memory subsystems requiring stable component supply across extended product lifecycles.

Supply support for SN74CBT3245AGQNR 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 SN74CBT3245AGQNR belongs to TI's CBT (Crossbar Bus Transceiver) family, engineered specifically for low-latency, low-distortion digital bus switching in space-constrained, high-density systems.

FAQ

What is the maximum continuous current per channel for the SN74CBT3245AGQNR?

The SN74CBT3245AGQNR supports a maximum continuous channel current of 128 mA, as specified in its absolute maximum ratings. This rating applies under recommended operating conditions (VCC = 4 V to 5.5 V, TA = −40°C to 85°C) and ensures reliable conduction without thermal runaway. Exceeding this current may degrade on-resistance stability or accelerate wear-out mechanisms in the integrated FETs. Always verify actual load current in the target application against this limit.

Does the SN74CBT3245AGQNR require external pull-up resistors on the OE pin?

Yes - to ensure high-impedance state during power-up or power-down, OE must be tied to VCC through a pull-up resistor. The minimum value depends on the current-sinking capability of the driving source; TI recommends calculating based on worst-case IIH (input high current) and desired noise margin. For robust operation in noisy environments, a 10-kΩ resistor is commonly used. Leaving OE floating risks undefined switching states and potential bus contention.

Can the SN74CBT3245AGQNR be used for analog signal switching?

Yes - the SN74CBT3245AGQNR is a bidirectional FET switch with rail-to-rail analog capability. It supports analog signals up to VCC (5.5 V max) with minimal distortion, thanks to its low 5-Ω on-resistance and 4-pF off-capacitance. However, it lacks built-in ESD protection beyond standard HBM ratings, so external TVS diodes are recommended for analog paths exposed to connectors or cables. Its TTL-compatible control interface remains digital-only.

What is the thermal pad (pin 21) connection requirement for the SN74CBT3245AGQNR?

Pin 21 is the exposed thermal pad of the GQN package and must be soldered to a dedicated PCB copper pour connected to GND. TI specifies this connection as mandatory for both thermal performance (reducing θJA from 78°C/W to ~45°C/W in optimized layouts) and mechanical reliability. The pad should be stencil-printed with 78% solder paste coverage and include ≥4 thermal vias (0.3-mm diameter, filled/plugged) to inner ground planes. Failure to connect pin 21 compromises long-term power handling and may cause early failure under sustained 100+ mA loads.

Is the SN74CBT3245AGQNR pin-compatible with older SN74CBT3245A variants in different packages?

Yes - the SN74CBT3245AGQNR shares identical pin functions and '245-type signal ordering with DW, DB, PW, and RGY variants. Signal pins A1–A8, B1–B8, OE, VCC, and GND occupy matching relative positions across all packages. However, physical pin numbering differs due to GQN's ball-grid layout (e.g., OE is pin 11 in GQN but pin 19 in DW), so PCB layout is not interchangeable. Schematic symbol and netlist remain identical - only footprint and assembly process change.