Texas Instruments SN74CBT3126DBQR

Overview

SN74CBT3126DBQR from Texas Instruments is a quadruple FET bus switch IC with independent 5-Ω bidirectional analog/digital signal paths, TTL-compatible control inputs, and latch-up immunity exceeding 250 mA per JESD 17 - used in high-speed data routing for PCI, memory expansion, and logic-level translation in industrial control backplanes.

For engineers reviewing the SN74CBT3126DBQR datasheet, SN74CBT3126DBQR pinout, SN74CBT3126DBQR application, or SN74CBT3126DBQR equivalent, this page delivers verified electrical specs (ron = 5–7 Ω), timing (tpd = 0.25 ns @ 5 V), thermal data (θJA = 90°C/W), and SSOP-16 package interface details critical for signal integrity validation and PCB layout.

Technical Context

This device implements four independent NMOS transmission-gate switches, each controlled by a dedicated OE input that places the A–B path in high-impedance state when low. It operates across 4 V to 5.5 V supply range with rail-to-rail analog switching capability and supports bidirectional signal flow without direction control pins.

Designed for hot-swap and power sequencing robustness, the SN74CBT3126DBQR features pulldown-recommended OE biasing to ensure defined high-Z state during power-up/down, and its 5 pF control-input capacitance enables clean edge transitions at >100 MHz clock rates in bus isolation applications.

Key Specifications

Pinout & Package

SN74CBT3126DBQR uses a 16-pin shrink small-outline package (SSOP-DBQ), 5.0 mm × 6.2 mm body, 0.65 mm lead pitch, 1.75 mm max height, with exposed pad not present. Pin 1 index located at top-left corner; pin numbering follows counterclockwise sequence from top-left.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBT3126DBQR, SN74CBTD3384DBQR offers double channel count but sacrifices 5 V operation and TTL compatibility, while 74LVC1G3157DP provides flexible single-pole routing in 6-pin format but requires four separate placements to match quad functionality - making SN74CBT3126DBQR optimal for compact, 5 V–compatible bus segmentation.

Availability

SN74CBT3126DBQR is available at Aetrix Electronics and suitable for industrial control backplanes, PCI-based instrumentation, memory expansion modules, and logic-level translation circuits requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74CBT3126DBQR 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-reliability logic and interface solutions.

The SN74CBT3126DBQR belongs to TI's CBT (Crossbar Bus Transceiver) family - engineered for low-latency, low-distortion signal routing in high-speed digital systems where deterministic timing and rail-to-rail analog switching are essential.

FAQ

What is the maximum continuous current rating per channel for SN74CBT3126DBQR?

The SN74CBT3126DBQR supports a continuous channel current of 128 mA per switch path, as specified in the Absolute Maximum Ratings table. This value reflects the safe DC conduction limit before thermal derating applies; actual usable current depends on ambient temperature, PCB copper area, and duty cycle. The SN74CBT3126DBQR must not exceed this rating even during transient conditions to avoid permanent damage.

Does SN74CBT3126DBQR support bidirectional signal flow without direction control pins?

Yes, the SN74CBT3126DBQR implements true bidirectional analog switching - signals pass freely between A and B terminals when OE is high, regardless of source/sink orientation. No direction pin or internal logic state is required, making it ideal for passive bus isolation and level translation. This behavior is inherent to its NMOS transmission-gate architecture and confirmed in the Function Table and Logic Diagram of the SN74CBT3126DBQR datasheet.

What is the recommended OE biasing strategy for SN74CBT3126DBQR during power-up?

To guarantee high-impedance state at power-up/power-down, each OE input of the SN74CBT3126DBQR must be tied to GND through a pulldown resistor. TI specifies the minimum resistor value based on driver sourcing capability - typically 10 kΩ suffices for most microcontroller outputs. Leaving OE floating risks undefined switch states and potential bus contention, which the SN74CBT3126DBQR design explicitly guards against via this requirement.

Can SN74CBT3126DBQR operate with a 3.3 V supply voltage?

No - the SN74CBT3126DBQR has a minimum recommended supply voltage of 4 V, as stated in the Recommended Operating Conditions table. At 3.3 V, the internal FETs fail to fully enhance, resulting in excessive on-resistance (>20 Ω), degraded timing, and possible logic threshold violations. For 3.3 V systems, consider TI's SN74CBTD series or alternative families explicitly rated down to 3.0 V, not the SN74CBT3126DBQR.

Is SN74CBT3126DBQR pin-compatible with other packages in the '126 family?

No - the SN74CBT3126DBQR uses a 16-pin DBQ (shrink SSOP) package with two NC pins (9 and 16), whereas D, DB, PW, and RGY variants use 14-pin footprints. Pinouts differ: DBQ relocates GND/VCC and adds NCs, breaking mechanical and electrical compatibility. Board designs must be revised when substituting SN74CBT3126DBQR for any 14-pin variant - it is not a drop-in replacement.