Texas Instruments SN74CB3Q3257PWE4

Overview

SN74CB3Q3257PWE4 from Texas Instruments is a 4-bit 1-of-2 FET multiplexer/demultiplexer bus switch optimized for high-bandwidth signal routing in low-voltage systems. It delivers rail-to-rail switching (0–5V with 3.3V V_CC), 4Ω typical on-state resistance, <0.32 ns propagation delay at 3.3V, and 5V-tolerant I/Os - enabling use in USB interface and optical networking signal gating applications.

For engineers reviewing the SN74CB3Q3257PWE4 datasheet, SN74CB3Q3257PWE4 pinout, SN74CB3Q3257PWE4 application, or SN74CB3Q3257PWE4 equivalent, key selection criteria include its 2.3–3.6V V_CC range, bidirectional zero-delay data flow, 3.5pF typical off-state I/O capacitance, and I_off-enabled partial-power-down capability for system-level power sequencing.

Technical Context

The SN74CB3Q3257PWE4 implements a charge-pump-enhanced FET switch architecture to maintain flat, low r_on across its 2.3–3.6V supply range, enabling consistent signal integrity up to 500MHz. Its dual 1-of-4 MUX/DEMUX structure uses independent OE and S inputs per channel group to support dynamic reconfiguration of 4-bit buses without timing skew.

Each of the four channels features symmetrical bidirectional I/O ports (A, B1, B2) with undershoot clamp diodes, 5V-tolerant operation regardless of V_CC state, and guaranteed isolation during power-up/down via I_off circuitry that limits backflow current to ≤1µA when V_CC = 0V.

Key Specifications

Pinout & Package

TSSOP-16 (PW) package: 5mm × 6.4mm body, 0.65mm pitch, exposed thermal pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CB3Q3257PWE4, SN74CBT3257PWR trades bandwidth and power-down safety for broader supply flexibility, while TS3A227EYZTR offers lower r_on but sacrifices pin compatibility and I_off - making SN74CB3Q3257PWE4 optimal for high-reliability, mixed-voltage, hot-pluggable 4-bit bus routing.

Availability

SN74CB3Q3257PWE4 is available at Aetrix Electronics and suitable for optical networking equipment, USB interface modules, and PBX voice bus isolation requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74CB3Q3257PWE4 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 signal-path solutions.

The SN74CB3Q3257PWE4 belongs to TI's CB3Q family of high-bandwidth FET bus switches, engineered specifically for low-distortion, rail-to-rail signal routing in broadband communications, optical infrastructure, and mixed-voltage computing systems.

FAQ

What is the maximum operating temperature for SN74CB3Q3257PWE4?

The SN74CB3Q3257PWE4 is rated for operation from –40°C to +105°C ambient temperature, as confirmed in Section 5.3 Recommended Operating Conditions of the official datasheet. This extended range supports deployment in industrial and telecom environments where thermal margins exceed standard commercial-grade limits. The TSSOP-16 package's thermal metrics (R_θJA = 112.7°C/W) ensure reliable junction temperatures under typical load conditions within this range. SN74CB3Q3257PWE4 maintains full electrical specifications across this entire span.

Does SN74CB3Q3257PWE4 support hot-swap or partial-power-down operation?

Yes, SN74CB3Q3257PWE4 explicitly supports partial-power-down via its I_off feature, limiting reverse current to ≤1µA when V_CC = 0V and VI/O = 0–5.5V. This allows safe insertion into live backplanes and prevents backfeeding between powered and unpowered subsystems. The datasheet confirms compliance with JESD78 Class II latch-up immunity (>100mA), and 5V-tolerant I/Os remain functional even during V_CC ramp-up or ramp-down. SN74CB3Q3257PWE4 is designed for such scenarios.

Can SN74CB3Q3257PWE4 interface between 1.8V and 3.3V logic domains?

Yes, SN74CB3Q3257PWE4 supports 0–5V signaling levels on its I/O ports regardless of V_CC, including 1.8V and 3.3V logic. Its 5V-tolerant I/Os accept inputs up to 7V, and rail-to-rail switching enables bidirectional translation without external level shifters. Control inputs (S, OE) accept TTL or CMOS logic thresholds compatible with both domains. SN74CB3Q3257PWE4 achieves this while maintaining 4Ω r_on and <0.32ns t_pd at 3.3V V_CC.

What is the recommended bypass capacitor for SN74CB3Q3257PWE4?

A 0.1µF ceramic capacitor is recommended directly at the V_CC pin (pin 16) of SN74CB3Q3257PWE4, placed as close as possible to minimize high-frequency noise and supply droop during fast switching events. TI's Power Supply Recommendations section specifies this value for single-supply devices like SN74CB3Q3257PWE4. For enhanced noise rejection, a parallel 1µF capacitor may be added, but the 0.1µF unit is mandatory for stable operation. SN74CB3Q3257PWE4 exhibits no internal V_CC splitting, so one capacitor suffices.

Is SN74CB3Q3257PWE4 pin-compatible with other packages in the same family?

No, SN74CB3Q3257PWE4 (TSSOP-16, PW) shares identical pinout and functionality with SN74CB3Q3257DBQR (SSOP-16), SN74CB3Q3257DGVR (TVSOP-16), and SN74CB3Q3257RGYR (VQFN-16), as verified in Figure 4-1 and Table 4-1 of the datasheet. All variants use the same 16-pin assignment: S, 1B1, 1B2, 1A, 2B1, 2B2, 2A, GND, 3A, 3B2, 3B1, 4A, 4B2, 4B1, OE, V_CC. SN74CB3Q3257PWE4 is thus a direct drop-in replacement across these packages when footprint and thermal constraints permit.