NXP Semiconductors CBTU4411EE,551

Overview

CBTU4411EE,551 from NXP Semiconductors is an 11-bit DDR2 SDRAM multiplexer/bus switch optimized for 1.7 V to 1.9 V VDD operation with SSTL_18 select inputs. It provides 1:4 channel selection across 11 host-to-DIMM data paths, features 12 Ω nominal ON-resistance, <30 ps output skew, and supports differential strobe configuration on channel 10 for DDR2 memory subsystems in 2-rank DIMM modules.

For engineers reviewing the CBTU4411EE,551 datasheet, CBTU4411EE,551 pinout, CBTU4411EE,551 application, or CBTU4411EE,551 equivalent, this device serves as a low-skew, low-propagation-delay bus switch for high-speed DDR2 data routing-requiring precise VREF biasing, VBIAS-controlled pull-down termination, and SSTL_18-compatible control timing.

Technical Context

The CBTU4411EE,551 implements a pseudo-differential SSTL_18 decoder using S0/S1 inputs referenced to VREF (0.49–0.51×VDD), enabling accurate switching time control independent of input slew rate. Its EN pin disables all 11 channels simultaneously into high-impedance, while STREN configures channel 10 for strobe-mode pull-up to 0.75×VDD when idle.

Each channel integrates a 400 Ω internal pull-down (Rpd = 280–520 Ω) tied to externally supplied VBIAS, and selectable Sn-input termination (RT = 55–105 Ω) activated by TERM. The design enforces single-active-DIMM-port operation and delivers matched rise/fall edge skew (<30 ps) critical for DDR2 400–800 Mbit/s data buses.

Key Specifications

Pinout & Package

LFBGA72 package: plastic low-profile fine-pitch ball grid array, 72-ball layout, 7 mm × 7 mm × 1.05 mm body. Ball pitch: 0.5 mm. Moisture Sensitivity Level (MSL): 3 per J-STD-020.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar DDR2 bus switch applications.

Compared with NCP4411MNR2G and PI3CH4411LEX, the CBTU4411EE,551 uniquely combines VREF-referenced SSTL_18 decode, VBIAS-programmable pull-down, and configurable strobe capability-making it the only option supporting full DDR2-compliant 2-rank DIMM timing and termination requirements.

Availability

CBTU4411EE,551 is available at Aetrix Electronics and suitable for DDR2 memory subsystems, 2-rank DIMM modules, and high-speed data bus multiplexing applications requiring stable component supply and long-term industrial lifecycle support.

Supply support for CBTU4411EE,551 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

NXP Semiconductors is a global semiconductor company specializing in secure connectivity solutions for automotive, industrial, and communication infrastructure markets.

The CBTU4411EE,551 belongs to NXP's DDR2 interface IC product line, designed specifically to solve signal integrity and routing challenges in high-density, high-speed memory subsystems operating at 200–400 MHz.

FAQ

What is the function of the VREF pin on the CBTU4411EE,551?

The VREF pin on the CBTU4411EE,551 supplies a precision reference voltage (0.49–0.51×VDD) to the pseudo-differential receivers for S0 and S1 select inputs. This ensures consistent switching thresholds and minimizes skew caused by input signal slew rate variations-critical for reliable 1:4 channel selection in DDR2 timing-critical applications. The CBTU4411EE,551 requires an externally filtered, low-noise VREF source.

How does the STREN pin affect channel 10 behavior in the CBTU4411EE,551?

When STREN is HIGH, channel 10 (HP10 and associated DIMM ports) operates in strobe mode: the unselected HP10 terminal is pulled up to 0.75×VDD via an internal resistor network, enabling differential DQS signaling. When STREN is LOW, channel 10 behaves identically to channels 0–9. This feature allows the CBTU4411EE,551 to serve both standard data and strobe routing functions without external components.

What is the purpose of the VBIAS pin on the CBTU4411EE,551?

The VBIAS pin on the CBTU4411EE,551 sets the effective resistance value of the internal 400 Ω pull-down (Rpd = 280–520 Ω) on all DIMM-port terminals (xDPn) when the switch is disabled. By applying a voltage between 0 V and 0.33×VDD to VBIAS, designers control termination strength to match DDR2 DIMM impedance requirements-ensuring clean signal decay during high-Z states without external resistors.

Can the CBTU4411EE,551 support 2-rank DDR2 SO-DIMMs?

Yes-the CBTU4411EE,551 is explicitly optimized for 1- or 2-rank DIMMs. Its 11-bit width matches DDR2 data bus requirements, its <30 ps output skew maintains timing alignment across ranks, and its VBIAS-controlled pull-down ensures proper termination when isolating Rank 0 and Rank 1 data paths. The CBTU4411EE,551 enables clean rank switching without signal integrity degradation.

What is the maximum data rate supported by the CBTU4411EE,551?

The CBTU4411EE,551 is characterized for use in DDR2 data buses operating from 400 Mbit/s to 800 Mbit/s (200 MHz to 400 MHz clock rates). Its 12 Ω ON-resistance, 50–100 ps propagation delay, and <30 ps skew meet JEDEC DDR2 timing specifications across the full commercial temperature range (0 °C to +85 °C). The CBTU4411EE,551 delivers deterministic performance at these speeds without external tuning.