Renesas 9DB633AGLFT

Overview

9DB633AGLFT from Renesas (formerly IDT) is a six-output, 0.7V current-mode differential HCSL zero-delay buffer optimized for PCIe Gen3 clock distribution. It supports 100 MHz input frequency, delivers <50 ps cycle-to-cycle jitter and <50 ps output-to-output skew, and operates across -40°C to +85°C with 3.3 V supply. It serves as a fanout buffer in server motherboard clock trees.

For engineers reviewing the 9DB633AGLFT datasheet, 9DB633AGLFT pinout, 9DB633AGLFT application, or 9DB633AGLFT equivalent, key selection criteria include PCIe Gen3 phase jitter compliance (<1.0 ps RMS), SMBus-controllable PLL bandwidth (0.4–4 MHz), dual OE# pins for ExpressCard power gating, and 28-pin TSSOP packaging with 0.65 mm pitch.

Technical Context

The 9DB633AGLFT implements a dual-mode PLL architecture-configurable via SMBus or pin strapping-to either clean incoming jitter (PLL mode) or pass through with minimal delay (bypass mode). Its PLL bandwidth is selectable between low (0.4–1 MHz) and high (2–4 MHz) ranges to suppress peaking in downstream CDRs while tracking spread-spectrum inputs.

It features six independent 0.7V HCSL differential output pairs, each with matched slew rate (±20%) and crossing voltage variation <140 mV. Input accepts 0.7V differential SRC clock; IREF pin sets output current via external 475 Ω resistor for 100 Ω differential termination.

Key Specifications

Pinout & Package

28-pin TSSOP package (4.4 mm × 9.7 mm body, 0.65 mm pitch), RoHS-compliant, tape-and-reel delivery (9DB633AGLFT).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PCIe clock buffer applications.

Compared with 9DB633AGLFT, the 9DB632AGLFT offers identical performance in a 4-output form factor with full pin compatibility, while the PI6C557-03LEX trades configurability and output count for smaller size and lower BOM cost-making it suitable only for non-critical, fixed-configuration PCIe clock trees.

Availability

9DB633AGLFT is available at Aetrix Electronics and suitable for server motherboard design, PCIe add-in card development, and industrial embedded systems requiring stable component supply and long-term lifecycle support.

Supply support for 9DB633AGLFT 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

Renesas Electronics Corporation is a global semiconductor leader delivering trusted embedded solutions for automotive, industrial, infrastructure, and IoT applications.

The 9DB633AGLFT belongs to Renesas' high-performance clock buffer product line, engineered specifically for PCIe Gen3–Gen5 reference clock distribution with ultra-low jitter, spread-spectrum compatibility, and industrial temperature resilience.

FAQ

What is the maximum input frequency supported by the 9DB633AGLFT in PLL mode?

The 9DB633AGLFT supports up to 110 MHz input frequency in PLL mode, as specified in the Electrical Characteristics table (Fipll max = 110 MHz). This accommodates PCIe Gen3 reference clocks (100 MHz) with margin for system-level variations and future-proofing. The device also operates down to 33 MHz, enabling backward compatibility with PCIe Gen1/Gen2 and other legacy clock sources. All specifications assume VDD = 3.3 V ±5% and ambient temperature within -40°C to +85°C.

Does the 9DB633AGLFT require external termination resistors for its HCSL outputs?

No, the 9DB633AGLFT does not require external series or parallel termination resistors for standard PCIe HCSL loads. Its 0.7V current-mode outputs are designed to drive 50 Ω single-ended (100 Ω differential) traces directly. The IREF pin sets output current via a single external 475 Ω resistor to ground, calibrating drive strength for precise 100 Ω differential impedance matching-eliminating per-output resistor networks and saving PCB area. This simplifies layout and improves signal integrity.

How does the SMBus interface of the 9DB633AGLFT enhance system-level clock management?

The SMBus interface of the 9DB633AGLFT enables dynamic, real-time control of PLL bandwidth and individual output enable/disable states without hardware modifications. For example, firmware can switch between high- and low-bandwidth PLL modes based on detected spread-spectrum modulation, or disable unused outputs to reduce power consumption in partial-link configurations. This capability is critical in adaptive server platforms where thermal and power budgets must be tightly managed-making the 9DB633AGLFT more flexible than pin-strapped-only alternatives.

What is the function of the vOE1# and vOE4# pins on the 9DB633AGLFT?

The vOE1# and vOE4# pins on the 9DB633AGLFT are active-low, internally pulled-down output enable controls that gate two independent groups of differential outputs: vOE1# controls DIF_0/DIF_1 pairs, and vOE4# controls DIF_4/DIF_5 pairs. Each pin supports hardware-level, glitch-free clock gating-essential for ExpressCard hot-plug compliance and power sequencing in PCIe add-in cards. Their internal 120 kΩ pull-down resistors ensure safe default-disabled state at power-up, eliminating risk of unintended clock injection during boot.

Is the 9DB633AGLFT compatible with PCIe Gen4 or Gen5 reference clock requirements?

The 9DB633AGLFT is explicitly designed and characterized for PCIe Gen3 (100 MHz, <1.0 ps RMS phase jitter) and backward-compatible with Gen1/Gen2. While its 110 MHz input limit and jitter performance meet Gen3 specs, it is not validated or guaranteed for Gen4 (125 MHz) or Gen5 (156.25 MHz) frequencies. Renesas does not specify additive jitter, duty cycle distortion, or phase noise behavior at those higher rates. For Gen4/Gen5 designs, newer devices such as the 9DBL0xxx family or Renesas' P1023/P1025 series should be selected-never assume upward compatibility without explicit manufacturer validation for the 9DB633AGLFT.