Texas Instruments CDCR83ADBQ

Overview

CDCR83ADBQ from Texas Instruments is a Direct Rambus™ clock generator IC designed to provide synchronized 400-MHz differential clock outputs (CLK/CLKB) for RDRAM subsystems, supporting 800-MHz data transfer rates. It features PLL-based frequency multiplication (4×, 6×, 8×, 16/3×), phase alignment between REFCLK and PCLKM/SYNCLKN inputs, fail-safe power-up initialization, and operation from a single 3.3-V supply with 70-mA typical supply current at 400 MHz.

For engineers reviewing the CDCR83ADBQ datasheet, CDCR83ADBQ pinout, CDCR83ADBQ application, or CDCR83ADBQ equivalent, this page delivers verified technical context-including PLL architecture, industrial temperature support (–40°C to 85°C), DBQ-24 package mapping, cycle-to-cycle jitter <50 ps at 400 MHz, and three selectable power modes-for Rambus memory timing validation and motherboard clock subsystem design.

Technical Context

The CDCR83ADBQ implements a PLL with integrated phase aligner that detects phase difference between PCLKM and SYNCLKN inputs and dynamically adjusts BUSCLK phase to minimize skew-enabling zero-latency crossing of the SYNCLK/PCLK boundary in Rambus memory controllers. Its gear-ratio logic supports synchronous communication between ASIC and Rambus channel clock domains.

It provides user-selectable operating modes via S0–S2 control pins: Normal (phase-aligned output), Bypass (PLLCLK pass-through), Test (REFCLK output), and Output Enable (Hi-Z). Frequency multiplication is set by MULT0/MULT1, enabling BUSCLK outputs from 267 MHz to 400 MHz with REFCLK inputs from 33 MHz to 100 MHz.

Key Specifications

Pinout & Package

Packaged in a 24-pin Shrink Small-Outline Package (DBQ), the CDCR83ADBQ uses a standard SSOP footprint with 0.64-mm lead pitch and JEDEC MO-153 compliance. Thermal performance is rated at 1400 mW at TA = 25°C, derating linearly to 740 mW at 85°C.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Direct Rambus clock generation applications.

Compared with CDCR83ADBQ, CDCR83ADBQR offers identical functionality with certified green packaging, while CDC924IDBQR serves a different architectural purpose-neither is pin-compatible nor functionally substitutable without redesigning the Rambus timing subsystem.

Availability

CDCR83ADBQ is available at Aetrix Electronics and suitable for desktop motherboard design, workstation memory controller integration, and server Rambus subsystem development requiring stable component supply, long-lifecycle support, and industrial-temperature qualification.

Supply support for CDCR83ADBQ 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 specializing in analog, embedded processing, and digital signal technologies, with over 50 years of leadership in precision timing and interface solutions.

The CDCR83ADBQ belongs to TI's Direct Rambus Clock Generator (DRCG) product line, engineered specifically to meet Rambus Inc.'s DRCG validation requirements for high-speed memory subsystems in desktop, workstation, and server platforms.

FAQ

What is the primary function of the CDCR83ADBQ in a Rambus memory system?

The CDCR83ADBQ serves as the core timing engine for Direct Rambus memory subsystems, generating a 400-MHz differential BUSCLK signal and actively aligning its phase to the PCLKM and SYNCLKN inputs from the memory controller. This ensures zero-latency data transfers across clock domains. The CDCR83ADBQ achieves this through an integrated PLL and phase aligner-eliminating the need for external timing compensation circuits in systems compliant with Rambus DRCG specifications.

Does the CDCR83ADBQ support spread spectrum clocking (SSC), and how is it implemented?

Yes, the CDCR83ADBQ supports spread spectrum clocking tracking capability to reduce electromagnetic interference. Unlike standalone SSC generators, it synchronizes to an incoming modulated reference clock and tracks the modulation in real time-requiring no external modulation source or configuration registers. This feature is built into the PLL architecture and operates transparently during normal mode, directly lowering peak EMI emissions without affecting timing accuracy or system compatibility.

What are the valid frequency combinations for REFCLK and BUSCLK on the CDCR83ADBQ?

The CDCR83ADBQ supports REFCLK inputs from 33 MHz to 100 MHz and generates BUSCLK outputs from 267 MHz to 400 MHz, depending on the MULT0/MULT1 setting. Valid combinations include: 67-MHz REFCLK × 4 = 267 MHz; 50-MHz REFCLK × 6 = 300 MHz; 67-MHz REFCLK × 6 = 400 MHz; 33-MHz REFCLK × 8 = 267 MHz; 50-MHz REFCLK × 8 = 400 MHz; and 67-MHz REFCLK × 16/3 ≈ 356 MHz. All configurations maintain cycle-to-cycle jitter under 50 ps at 400 MHz.

How does the CDCR83ADBQ handle power-up sequencing and initialization reliability?

The CDCR83ADBQ incorporates a fail-safe power-up initialization state machine that guarantees deterministic behavior under all supply ramp conditions-including monotonic, non-monotonic, and partially powered scenarios. It requires no external reset signal and automatically configures internal registers and PLL lock sequence upon VDD stabilization. This ensures consistent timing alignment and eliminates boot-time clock glitches-a critical requirement for Rambus memory subsystems where misaligned startup can cause system hang or data corruption.

Can the CDCR83ADBQ be used in mobile or battery-powered applications, and what power-saving features does it offer?

Yes, the CDCR83ADBQ is explicitly designed for mobile and power-sensitive applications, offering three distinct low-power states: Normal (70 mA at 400 MHz), CLK Stop (30 mA, outputs held in defined state), and Power-down (100 µA, internal circuitry disabled). These modes are controlled via dedicated STOPB and PWRDNB pins with sub-millisecond transition times. The CDCR83ADBQ maintains full functionality and configuration retention in all states-enabling rapid wake-up without PLL relock delay, which is essential for responsive mobile platform power management.