Texas Instruments SN74CBTLV3857DBQR

Overview

SN74CBTLV3857DBQR from Texas Instruments is a 10-bit FET bus switch designed for 3-V to 3.6-V operation with SSTL_2-compatible enable input, 10-kΩ pulldown resistors on B-port pins, rail-to-rail switching, and I_off support for partial-power-down mode-used in DDR SDRAM data-path termination and signal isolation.

For engineers reviewing the SN74CBTLV3857DBQR datasheet, SN74CBTLV3857DBQR pinout, SN74CBTLV3857DBQR application, or SN74CBTLV3857DBQR equivalent, key selection criteria include on-state resistance (7–13 Ω), propagation delay (0.25 ns), OE AC threshold compatibility with V_REF ±350 mV, internal pullup/pulldown resistor values, and flow-through PCB layout optimization.

Technical Context

This device implements a passive FET-based bidirectional switch architecture with no internal logic or level-shifting circuitry. Each of the 10 channels operates as an analog pass gate controlled solely by the OE signal, with V_REF (0.38 × V_CC) defining SSTL_2-compatible input thresholds.

It supports rail-to-rail signal integrity across A/B ports, features integrated 10-kΩ pulldowns on all B-port terminals and a 50-kΩ pullup on OE, and guarantees isolation during power-off via I_off protection that blocks backflow current when V_CC = 0 V.

Key Specifications

Pinout & Package

SN74CBTLV3857DBQR is housed in a 24-pin QSOP (DBQ) package with 0.65-mm lead pitch and flow-through pin arrangement optimized for minimal trace stubs in high-speed DDR layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 10-bit FET bus switch applications.

Compared with SN74CBTLV3861DBQR and SN74CBT3244DBQR, the SN74CBTLV3857DBQR uniquely combines 10-bit width, V_REF-based SSTL_2 OE compatibility, and integrated B-port pulldowns-making it the only option qualified for drop-in DDR SDRAM data-path replacement without redesign.

Availability

SN74CBTLV3857DBQR is available at Aetrix Electronics and suitable for DDR SDRAM interface isolation, memory subsystem multiplexing, and partial-power-down embedded memory systems requiring stable component supply and long-term industrial availability.

Supply support for SN74CBTLV3857DBQR 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 delivering analog, embedded processing, and logic solutions with emphasis on reliability, precision, and system-level integration.

The SN74CBTLV3857DBQR belongs to TI's CBTLV (Crossbar TTL Very-Low-Voltage) logic family-designed specifically for high-speed, low-voltage DDR memory interface applications requiring minimal propagation delay and precise SSTL_2 compatibility.

FAQ

What is the function of V_REF on the SN74CBTLV3857DBQR?

V_REF sets the reference voltage (0.38 × V_CC) used to define the AC and DC input thresholds for the OE pin. It enables precise SSTL_2-compatible enable control without external resistive dividers. The SN74CBTLV3857DBQR requires V_REF to be externally supplied and decoupled to ensure stable VIH/VIL windows across temperature and voltage variations.

Does the SN74CBTLV3857DBQR support hot insertion or partial-power-down operation?

Yes-the SN74CBTLV3857DBQR features I_off protection that actively blocks current backflow when V_CC = 0 V, making it suitable for hot-plug and partial-power-down memory interfaces. This capability is verified per JESD 78 Class II latch-up testing and allows safe operation in mixed-power-domain DDR systems without additional isolation circuitry.

What is the typical on-state resistance (r_on) of the SN74CBTLV3857DBQR and how does it affect DDR design?

The SN74CBTLV3857DBQR has a typical r_on of 7 Ω at V_CC = 3 V and 24 mA drive. This low resistance eliminates the need for external series termination resistors in SSTL_2 DDR data paths, reducing component count and PCB area while maintaining signal integrity and timing margins up to 200 Mbit/s DDR rates.

Are the B-port pins of the SN74CBTLV3857DBQR internally terminated, and if so, to what value?

Yes-the SN74CBTLV3857DBQR integrates 10-kΩ pulldown resistors to GND on each B1–B10 pin. These resistors ensure defined logic-low states on the SDRAM side when the switch is disabled, preventing floating inputs and eliminating the need for external termination components in DDR memory interfaces.

Can the SN74CBTLV3857DBQR be used in place of a standard logic buffer or level shifter?

No-the SN74CBTLV3857DBQR is a passive analog FET switch, not a logic buffer or level shifter. It provides no voltage translation, signal amplification, or logic inversion. Its operation depends entirely on V_CC and signal swing; using it outside its specified 3-V to 3.6-V rail-to-rail range may degrade r_on and timing performance. The SN74CBTLV3857DBQR must be applied strictly as a bidirectional switch in compatible SSTL_2 environments.