Texas Instruments SN74CBT3257CPWRG4

Overview

SN74CBT3257CPWRG4 from Texas Instruments is a 4-bit 1-of-2 FET multiplexer/demultiplexer with bidirectional signal routing, 3 Ω typical ON-state resistance, <0.24 ns propagation delay at 4 V, and −2 V undershoot protection on A/B ports. It operates from 4 V to 5.5 V and supports 0–5 V logic levels across USB interface and bus isolation applications.

For engineers reviewing the SN74CBT3257CPWRG4 datasheet, SN74CBT3257CPWRG4 pinout, SN74CBT3257CPWRG4 application, or SN74CBT3257CPWRG4 equivalent, key selection criteria include Ioff partial-power-down capability, 5.5 pF typical OFF-state B-port capacitance, TTL/CMOS-compatible control inputs, and TSSOP-16 package compatibility with high-density PCB layouts.

Technical Context

The SN74CBT3257CPWRG4 implements four independent analog/digital SPDT switches controlled by a shared select (S) input and global output-enable (OE). Each switch uses low-threshold FETs with active undershoot-protection circuitry that clamps A/B port voltages down to −2 V while maintaining OFF-state isolation.

Its Ioff specification ensures no backflow current during partial power-down, and its 0–5 V data I/O tolerance enables level-shifting between mixed-voltage domains (e.g., 1.8 V MCU ↔ 3.3 V peripheral), with control inputs compatible with both TTL and 5 V/3.3 V CMOS logic thresholds.

Key Specifications

Pinout & Package

TSSOP-16 package (PW), 5.0 mm × 4.4 mm footprint, 1.2 mm max height, 0.65 mm lead pitch, exposed pad not present.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar FET multiplexer applications.

Compared with SN74CBTD3384PWR and 74LVC1G3157DP,125, the SN74CBT3257CPWRG4 uniquely balances 4-channel density, −2 V undershoot hardening, and 0–5 V interoperability - making it optimal for USB docking, modular I/O, and multi-rail embedded signal routing where reliability and voltage flexibility are prioritized over minimal channel count or ultra-low ICC.

Availability

SN74CBT3257CPWRG4 is available at Aetrix Electronics and suitable for USB interface design, industrial bus isolation, low-distortion analog gating, and multi-voltage logic translation requiring stable component supply and long-term manufacturability.

Supply support for SN74CBT3257CPWRG4 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 high-reliability interface IC development.

The SN74CBT3257CPWRG4 belongs to TI's CBT (Crossbar Bus Transceiver) family, engineered for high-speed, low-distortion signal routing in mixed-voltage systems where robustness against transients and precise timing control are essential.

FAQ

What is the maximum undershoot voltage the SN74CBT3257CPWRG4 can withstand on its A and B ports?

The SN74CBT3257CPWRG4 provides active undershoot protection up to −2 V on both A and B ports, as verified in the absolute maximum ratings and undershoot characteristics section of the official datasheet. This protection remains effective regardless of VCC state and ensures the switch stays reliably OFF during negative transients, which is critical in USB hot-plug scenarios. The SN74CBT3257CPWRG4 achieves this via integrated clamping circuitry that responds dynamically to sub-ground excursions without compromising isolation.

Does the SN74CBT3257CPWRG4 support level-shifting between different logic families?

Yes, the SN74CBT3257CPWRG4 supports true bidirectional level-shifting across 0.8 V, 1.2 V, 1.5 V, 1.8 V, 2.5 V, 3.3 V, and 5 V logic domains. Its 0–5.5 V data I/O voltage range and TTL/CMOS-compatible control inputs (VIH = 2 V min, VIL = 0.8 V max) allow direct connection between disparate voltage rails without external biasing. The SN74CBT3257CPWRG4 maintains signal integrity through low ron and matched ON-resistance, making it suitable for I²C expansion and mixed-voltage MCU-peripheral interfaces.

What is the thermal performance of the SN74CBT3257CPWRG4 in its TSSOP-16 package?

The SN74CBT3257CPWRG4 in the PW (TSSOP-16) package has a thermal impedance θJA of 108°C/W, as specified in the absolute maximum ratings table. This value assumes standard JEDEC high-K test board conditions. For sustained operation near maximum ratings, localized copper pour and thermal vias under the package body are recommended. The SN74CBT3257CPWRG4 does not include an exposed thermal pad, so heatsinking relies on PCB layout optimization rather than package-level conduction.

Can the SN74CBT3257CPWRG4 be used in analog signal paths such as audio or sensor conditioning?

Yes, the SN74CBT3257CPWRG4 is qualified for analog signal routing due to its low 3 Ω typical ON-state resistance, 16.5 pF Cio(ON), and flat frequency response. Its FET-based architecture ensures symmetrical conduction and minimal THD, supporting line-level audio gating and precision sensor signal switching. The SN74CBT3257CPWRG4 maintains channel-to-channel crosstalk below −60 dB at 1 MHz and exhibits no DC offset - validated in electrical characteristics and switching waveform measurements.

How does the Ioff feature of the SN74CBT3257CPWRG4 protect systems during partial power-down?

The Ioff feature limits current to ≤10 µA when VCC = 0 V, preventing backflow from live I/O lines into a powered-down supply domain. This protects downstream circuitry from latch-up, unintended biasing, or damage during hot-swap, firmware update, or modular power sequencing. The SN74CBT3257CPWRG4 achieves this via internal transistor cutoff and isolation structures confirmed in JESD 78 Class II latch-up testing (>100 mA), ensuring robust operation in industrial and automotive subsystems with staggered power domains.