Texas Instruments SN74CBT3257CDRG4

Overview

SN74CBT3257CDRG4 from Texas Instruments is a 4-bit 1-of-2 FET multiplexer/demultiplexer with bidirectional signal flow, 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 signaling across mixed-voltage systems including USB interface and I²C bus expansion.

For engineers reviewing the SN74CBT3257CDRG4 datasheet, SN74CBT3257CDRG4 pinout, SN74CBT3257CDRG4 application, or SN74CBT3257CDRG4 equivalent, key selection criteria include its I_off-enabled partial-power-down capability, 5.5 pF typical OFF-state B-port capacitance, TTL/CMOS-compatible control inputs, and SOIC-16 package compatibility with industrial bus isolation designs.

Technical Context

The SN74CBT3257CDRG4 implements four independent analog/digital SPDT switches controlled by a shared select (S) and output-enable (OE) input. Each switch uses low-threshold FETs with active undershoot-protection circuitry that clamps A/B port voltages down to −2 V while maintaining high-impedance isolation when disabled.

Its I_off feature guarantees no backflow current during partial power-down, and its 0–5 V data I/O tolerance enables seamless interfacing between 1.8 V, 2.5 V, 3.3 V, and 5 V domains without level shifters-critical for mixed-signal bus gating in embedded controllers and peripheral hubs.

Key Specifications

Pinout & Package

SN74CBT3257CDRG4 is housed in a 16-pin SOIC (D) package measuring 9.9 mm × 3.91 mm × 1.45 mm (max height), with standard 1.27 mm pitch, RoHS-compliant NiPdAu lead finish, and moisture sensitivity level (MSL) 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3257CDRG4, SN74CBTD3384CDW offers higher channel density but sacrifices voltage flexibility and transient robustness, while TS3A226AEYFFR delivers lower resistance at the expense of 5 V compatibility and undershoot protection-making SN74CBT3257CDRG4 the optimal choice for industrial USB and mixed-rail bus isolation.

Availability

SN74CBT3257CDRG4 is available at Aetrix Electronics and suitable for USB interface design, industrial bus isolation, and mixed-voltage sensor interfacing requiring stable component supply, long-term manufacturability, and TI-qualified production lots.

Supply support for SN74CBT3257CDRG4 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 SN74CBT3257C family was engineered for high-speed, low-distortion signal routing in mixed-voltage digital systems-targeting USB, I²C, and industrial control applications demanding robust transient immunity and seamless voltage domain bridging.

FAQ

What is the maximum signal frequency supported by SN74CBT3257CDRG4?

The SN74CBT3257CDRG4 supports signal frequencies up to 500 MHz in practical applications due to its 3 Ω typical ON-state resistance and 5.5 pF OFF-state B-port capacitance, yielding a bandwidth exceeding 1 GHz in low-impedance configurations. Measured propagation delay remains below 0.24 ns, making it suitable for USB 2.0 (480 Mbps) and fast I²C (1 MHz) signal routing without degradation.

Does SN74CBT3257CDRG4 require external pull-up resistors on OE or S pins?

Yes-TI recommends tying OE to V_CC through a pull-up resistor during power-up/down to guarantee high-impedance state initialization; minimum value depends on driver sink strength but typically ranges from 4.7 kΩ to 10 kΩ. The S pin may be driven directly from CMOS/TTL outputs without pull-ups when actively controlled.

Can SN74CBT3257CDRG4 be used in analog signal paths such as audio or sensor conditioning?

Yes-SN74CBT3257CDRG4 is specified for both digital and analog applications. Its flat r_on (3 Ω typ), low charge injection (<10 pC), and 5.5 pF OFF-capacitance support audio line switching and precision sensor multiplexing up to 100 kHz with minimal THD and crosstalk, provided signal swing stays within 0–5 V and current remains ≤±128 mA.

Is SN74CBT3257CDRG4 compatible with lead-free reflow profiles?

Yes-SN74CBT3257CDRG4 carries MSL Level-1 rating (unlimited floor life) and is qualified for peak reflow temperatures up to 260°C per JEDEC J-STD-020. Its NiPdAu lead finish ensures reliable solder joint formation under standard lead-free reflow profiles, including ramp-soak-reflow cycles with 60–90 second exposure above 217°C.

How does the undershoot protection circuit in SN74CBT3257CDRG4 operate during hot-plug events?

The undershoot protection circuit in SN74CBT3257CDRG4 actively monitors A/B port voltages and disables internal FET conduction if either drops below −2 V-even when OE is asserted-preventing false turn-on and latch-up. This occurs independently of control logic, ensuring robustness during USB cable insertion, ESD discharge, or power sequencing mismatches.