Texas Instruments SN74CBT3245CDBQR

Overview

SN74CBT3245CDBQR from Texas Instruments is an 8-bit bidirectional FET bus switch IC with near-zero propagation delay (0.15 ns typical at 5 V), 3 Ω typical ON-state resistance, and undershoot protection up to −2 V on both A and B ports. It operates from 4 V to 5.5 V, supports 0–5 V signaling across multiple logic families (TTL, 1.2 V–5 V CMOS), and enables low-distortion signal gating in high-speed digital interconnects.

For engineers reviewing the SN74CBT3245CDBQR datasheet, SN74CBT3245CDBQR pinout, SN74CBT3245CDBQR application, or SN74CBT3245CDBQR equivalent, this device is selected for bus isolation, memory interleaving, and USB interface signal routing where minimal insertion loss, rail-to-rail voltage translation, and partial-power-down robustness are required.

Technical Context

The SN74CBT3245CDBQR implements eight independent FET transmission gates controlled by a single active-low OE input. When enabled (OE = low), it establishes low-impedance bidirectional paths between corresponding A1–A8 and B1–B8 terminals, with r_on = 3 Ω typical ensuring minimal RC delay and signal distortion.

Its I_off feature blocks backflow current during partial power-down, while integrated undershoot-protection circuitry clamps A/B port voltages down to −2 V without latch-up-verified per JESD 78 Class II (>100 mA) and ESD-rated to 2000 V HBM.

Key Specifications

Pinout & Package

SN74CBT3245CDBQR uses a 20-pin SSOP (DBQ) package, 7.4 mm × 5.6 mm body, 0.65 mm pitch, 2.0 mm max height, with exposed thermal pad not present (unlike QFN). Pin 1 index located at top-left corner with beveled edge marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3245CDBQR, SN74CBTD3384CDBQR offers higher channel count but sacrifices undershoot protection and voltage flexibility, while 74LVC245APW,118 adds direction logic overhead and latency-making SN74CBT3245CDBQR optimal for low-skew, mixed-voltage, bidirectional isolation.

Availability

SN74CBT3245CDBQR is available at Aetrix Electronics and suitable for USB interface design, memory interleaving architectures, and industrial bus isolation requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN74CBT3245CDBQR 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 decades of expertise in high-speed logic and interface solutions.

The SN74CBT3245CDBQR belongs to TI's CBT (Crossbar Bus Transceiver) family, engineered for ultra-low-latency, low-distortion signal routing in high-speed digital systems where traditional logic buffers introduce unacceptable timing or loading penalties.

FAQ

What is the maximum data rate supported by the SN74CBT3245CDBQR?

The SN74CBT3245CDBQR does not specify a maximum data rate in its datasheet because it functions as a passive FET switch-not a serial transceiver. Its 0.15 ns propagation delay and 5.5 pF off-capacitance enable reliable operation with NRZ signals up to 500 Mbps in typical PCB layouts. Actual usable rate depends on trace impedance, load capacitance, and signal integrity margins-not an inherent limit of the SN74CBT3245CDBQR itself.

Can the SN74CBT3245CDBQR operate with 3.3 V logic levels on the A/B ports while powered at 5 V?

Yes. The SN74CBT3245CDBQR explicitly supports 0–5 V signaling on A/B ports regardless of VCC (4–5.5 V). This allows direct interfacing between 3.3 V peripherals and 5 V controllers without level shifters. The device's FET architecture ensures rail-to-rail voltage translation, and its 5.5 pF C_io(OFF) prevents loading-induced timing errors-key for mixed-voltage designs using SN74CBT3245CDBQR.

Is a pull-up resistor required on the OE pin of the SN74CBT3245CDBQR?

Yes. To ensure high-impedance state during power-up or brownout, OE must be tied to VCC through a pull-up resistor. TI recommends ≥10 kΩ for standard CMOS drivers. Without it, OE may float, causing undefined switch states and potential bus contention. This requirement applies to every SN74CBT3245CDBQR unit in system-level designs to guarantee deterministic behavior at power-on reset.

Does the SN74CBT3245CDBQR support hot-swap or live-insertion applications?

Yes-the SN74CBT3245CDBQR supports partial-power-down via its I_off feature (10 µA max at VCC = 0 V), which blocks current backflow when VCC is unpowered. Combined with −2 V undershoot protection and JESD 78 Class II latch-up immunity (>100 mA), it safely isolates live backplanes or hot-pluggable modules. However, external current limiting remains necessary for sustained overvoltage beyond absolute max ratings.

How does the undershoot protection circuitry in the SN74CBT3245CDBQR work?

The SN74CBT3245CDBQR integrates dedicated undershoot-protection circuitry on each A and B port that detects voltage excursions below −2 V and forces the internal FETs into a guaranteed OFF state-even if OE is asserted. This prevents false conduction, latch-up, or damage during ESD events or inductive transients. The protection is active independently per port and requires no external components, making SN74CBT3245CDBQR robust in electrically noisy environments like factory automation or automotive gateways.