Texas Instruments SN74CBTLV3857DW

Overview

SN74CBTLV3857DW from Texas Instruments is a 10-bit FET bus switch designed for 3-V to 3.6-V operation with SSTL_2-compatible OE input, 7–13 Ω on-state resistance (VCC = 3 V), 0.25 ns propagation delay, and integrated 10-kΩ B-port pulldowns-used in DDR SDRAM data path termination and signal isolation.

For engineers reviewing the SN74CBTLV3857DW datasheet, SN74CBTLV3857DW pinout, SN74CBTLV3857DW application, or SN74CBTLV3857DW equivalent, key selection criteria include SSTL_2 OE compatibility, rail-to-rail switching, Ioff partial-power-down support, and flow-through SOIC-24 layout optimization for high-speed memory interfaces.

Technical Context

This device implements a 10-channel bidirectional FET switch with single active-low OE control, enabling/disabling all A↔B paths simultaneously. Its on-resistance profile (7–13 Ω at VCC = 3 V) is calibrated to replace external series termination resistors in SSTL_2 DDR data buses.

The internal 10-kΩ pulldown resistors on all B-port pins and 50-kΩ pullup on OE ensure defined logic states during power-up/down and idle conditions. Ioff protection prevents backflow current when VCC = 0, supporting partial-power-down system architectures.

Key Specifications

Pinout & Package

SN74CBTLV3857DW uses a 24-pin SOIC (DW) package with 1.27-mm pitch, 7.5-mm body width, and thermal resistance θJA = 46°C/W - optimized for standard PCB assembly and moderate-power DDR routing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBTLV3857DW, SN74CBT3244DW lacks SSTL_2 OE support and B-port pulldowns, increasing design complexity; SN74CBTLV3245ADW provides matching OE compatibility but requires external biasing, raising BOM cost and layout effort.

Availability

SN74CBTLV3857DW is available at Aetrix Electronics and suitable for DDR SDRAM interfaces, memory module isolation, and SSTL_2 signal routing requiring stable component supply across industrial temperature ranges (−40°C to 85°C).

Supply support for SN74CBTLV3857DW 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 logic solutions, with decades of DDR interface innovation and JEDEC-compliant product development.

The SN74CBTLV3857DW belongs to TI's CBTLV logic family, engineered specifically for high-speed, low-voltage memory interconnects - delivering precise on-resistance matching, SSTL_2 signal conditioning, and robust partial-power-down behavior.

FAQ

What is the function of the VREF pin on the SN74CBTLV3857DW?

The VREF pin on the SN74CBTLV3857DW sets the reference voltage for SSTL_2–compatible OE input thresholds (VIH = VREF + 350 mV, VIL = VREF − 350 mV). It must be driven at 0.38 × VCC - typically 1.15–1.35 V across the 3–3.6 V operating range - to ensure correct OE interpretation in DDR systems. The SN74CBTLV3857DW does not generate VREF internally; an external source or resistor divider is required.

Does the SN74CBTLV3857DW support partial-power-down operation?

Yes, the SN74CBTLV3857DW supports partial-power-down operation via its Ioff feature. When VCC = 0 V, the device blocks current flow between A and B ports, preventing backdrive damage from live signals on either side. This capability is verified per JESD 78 Class II latch-up testing and is critical for hot-plug DDR memory modules and mixed-supply systems where SN74CBTLV3857DW remains unpowered while adjacent circuits operate.

What is the purpose of the internal 10-kΩ pulldown resistors on the B port of the SN74CBTLV3857DW?

The internal 10-kΩ pulldown resistors on B1–B10 of the SN74CBTLV3857DW ensure a defined logic-low state on the SDRAM side when OE is high (switch open) or during power-up/power-down sequences. This eliminates floating inputs that could cause undefined memory behavior or increased EMI, and removes the need for 10 discrete external resistors - simplifying layout and reducing BOM count in DDR SDRAM designs using SN74CBTLV3857DW.

Can the SN74CBTLV3857DW be used in place of a series termination resistor in DDR applications?

Yes, the SN74CBTLV3857DW is explicitly designed to replace discrete series termination resistors in SSTL_2 DDR data paths. Its typical on-state resistance of 7–13 Ω (at VCC = 3 V) matches the target impedance for DDR signal integrity, eliminating the need for ten separate 25-Ω resistors. This integration reduces PCB area, improves timing consistency, and lowers assembly cost - a core design objective confirmed in the SN74CBTLV3857DW datasheet.

What package type and pin count does the SN74CBTLV3857DW use?

The SN74CBTLV3857DW uses a 24-pin SOIC (DW) package with 1.27-mm lead pitch and 7.5-mm body width. This surface-mount package supports standard reflow profiles (MSL Level-1, 260°C peak), offers θJA = 46°C/W thermal performance, and features a flow-through pinout - A1–A10 on one side and B1–B10 on the opposite side - to minimize trace length in DDR routing. The DW suffix in SN74CBTLV3857DW unambiguously identifies this package variant.