Texas Instruments SN74CBTLV3857PWR

Overview

SN74CBTLV3857PWR from Texas Instruments is a 10-bit FET bus switch optimized for 3.3-V SSTL-2 DDR SDRAM data paths, featuring 7–13 Ω on-state resistance, rail-to-rail switching, and integrated 10-kΩ B-port pulldowns. It replaces series termination resistors in DDR memory interfaces and supports partial-power-down via Ioff.

For engineers reviewing the SN74CBTLV3857PWR datasheet, SN74CBTLV3857PWR pinout, SN74CBTLV3857PWR application, or SN74CBTLV3857PWR equivalent, key selection criteria include SSTL-2-compatible OE input (VREF ±350 mV AC threshold), 0.25 ns propagation delay, 24-pin TSSOP package, and Ioff-enabled isolation during power-down.

Technical Context

This device implements a flow-through architecture with 10 independent bidirectional FET switches, each controlled by a single active-low OE signal referenced to VREF = 0.38 × VCC. Its design eliminates external series termination in DDR SDRAM data buses by matching characteristic impedance through controlled on-resistance.

The internal 10-kΩ pulldown resistors on all B-port pins and 50-kΩ pullup on OE ensure defined logic states during initialization or high-impedance operation. Ioff functionality blocks current backflow when VCC = 0, enabling safe partial-power-down in multi-rail DDR systems.

Key Specifications

Pinout & Package

TSSOP-24 (PW) package: 7.8 mm × 4.4 mm body, 0.65 mm pitch, exposed pad not present, RoHS-compliant NiPdAu finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74CBTLV3857PWR, SN74CBT3857PWR lacks SSTL-2 support and B-port pulldowns-making it unsuitable for DDR termination replacement-while SN74LVC1G3157DCKR offers lower ron but no multi-bit integration or DDR-specific biasing, increasing layout complexity and component count in memory interface designs.

Availability

SN74CBTLV3857PWR is available at Aetrix Electronics and suitable for DDR SDRAM memory interfaces, registered DIMM buffering, and DDR2 address/control routing requiring stable component supply, consistent parametric performance, and long-term industrial availability.

Supply support for SN74CBTLV3857PWR 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 company headquartered in Dallas, Texas, delivering analog, embedded processing, and digital signal processing technologies since 1930.

The SN74CBTLV3857PWR belongs to TI's CBTLV (Crossbar TTL) family, engineered specifically for high-speed, low-voltage memory interface applications including DDR SDRAM, where precise impedance control and SSTL-2 compatibility are critical.

FAQ

What is the function of the VREF pin on the SN74CBTLV3857PWR?

The VREF pin on the SN74CBTLV3857PWR sets the reference voltage for SSTL-2-compatible OE input thresholds (VIH = VREF + 350 mV, VIL = VREF − 350 mV). It is internally generated as 0.38 × VCC but must be externally bypassed to stabilize DDR timing margins. This ensures the SN74CBTLV3857PWR synchronizes precisely with DDR clock and command signals sharing the same VREF source.

Does the SN74CBTLV3857PWR require external pull-up or pull-down resistors on its B-port pins?

No, the SN74CBTLV3857PWR includes internal 10-kΩ pulldown resistors on all B1–B10 pins, eliminating the need for external resistors in DDR SDRAM interface designs. This feature reduces BOM count and PCB area while ensuring defined logic states during initialization or high-impedance operation-key for reliable DDR memory boot sequences and hot-plug scenarios involving the SN74CBTLV3857PWR.

Can the SN74CBTLV3857PWR be used in DDR2 or DDR3 systems?

The SN74CBTLV3857PWR is specified for DDR SDRAM (200 Mbit/s double-data-rate) and compatible with DDR2 address/control signaling due to its 3.3-V operation and SSTL-2 thresholds, but it is not rated for DDR3's 1.5-V VDDQ or SSTL-15 levels. For DDR3 data paths, TI recommends newer families like the SN74AVC series. The SN74CBTLV3857PWR remains optimal for DDR and DDR2 memory subsystems where its 7–13 Ω ron and VREF-referenced OE deliver verified performance.

What is the significance of Ioff support in the SN74CBTLV3857PWR?

Ioff support in the SN74CBTLV3857PWR ensures that no damaging current flows between A and B ports when VCC = 0, enabling safe partial-power-down operation in multi-rail DDR systems. This allows memory controllers to power down the SN74CBTLV3857PWR supply independently while B-port signals remain active-critical for power-gating strategies in servers and embedded systems using the SN74CBTLV3857PWR as a DDR data switch.

How does the flow-through architecture of the SN74CBTLV3857PWR improve PCB layout?

The flow-through architecture of the SN74CBTLV3857PWR arranges A1–A10 on one side and B1–B10 on the opposite side, enabling straight-through PCB trace routing with minimal layer transitions or vias. This reduces signal path asymmetry, crosstalk, and impedance discontinuities-especially beneficial in dense DDR layouts where the SN74CBTLV3857PWR serves as a data bus bridge between controller and memory, improving timing margin and EMI performance.