Microchip Technology SY69753ALHG

Overview

SY69753ALHG from Micrel Inc. is a 3.3V clock and data recovery (CDR) IC for SONET/SDH OC-3/STS-3 systems, supporting 125Mbps and 155Mbps NRZ data streams with on-chip VCO-based PLL lock, differential PECL I/O, and link fault detection. It operates across –40°C to +85°C and delivers recovered clock (RCLK/TCLK) and retimed data (RDOUT) outputs in a 32-pin EPAD-TQFP package.

For engineers reviewing the SY69753ALHG datasheet, SY69753ALHG pinout, SY69753ALHG application, or SY69753ALHG equivalent, this device serves as a low-power CDR solution requiring precise jitter tolerance, reference clock selection (via DIVSEL1/DIVSEL2), carrier detect (CD) control, and dual-loop PLL architecture for robust lock acquisition in telecom line interfaces.

Technical Context

The SY69753ALHG implements two independent PLLs: one receiver PLL for clock/data recovery from RDINP/RDINN inputs, and one frequency synthesis PLL using REFCLK as reference to generate TCLK. The VCO center frequency ranges from 720MHz to 1250MHz, with ±5% tolerance and 15µs typical acquisition lock time.

It supports selectable divide ratios (8×, 10×, 16×, 20×) between REFCLK and RCLK/TCLK via TTL DIVSEL1/DIVSEL2 inputs, and allows dynamic clock source selection (recovered RCLK vs. synthesized TCLK) via CLKSEL. Link fault indication (LFIN) asserts HIGH when RDIN is within ±1000ppm of the PLL's tracking range and CD is HIGH.

Key Specifications

Pinout & Package

SY69753ALHG is housed in a 32-pin EPAD-TQFP (package code H32-1) with exposed thermal pad, θJA = 20°C/W at 500lfpm airflow. Power pins are segregated (VCC, VCCA, VCCO) and share same 3.3V rail; analog ground (GNDA) and digital ground (GND) are separated for noise isolation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar clock and data recovery applications.

Compared with SY87701AL and SY89322V, SY69753ALHG uniquely integrates carrier detect control, industrial-grade low-power CDR, and SONET-optimized loop response-making it the sole fit for cost-sensitive, fixed-rate OC-3 line interface designs requiring guaranteed lock stability and minimal external components.

Availability

SY69753ALHG is available at Aetrix Electronics and suitable for SONET OC-3 line cards, Ethernet media converters, and proprietary 120–180Mbps serial links requiring stable component supply, long-term lifecycle support, and Pb-free compliance.

Supply support for SY69753ALHG 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

Micrel Inc. was a fabless semiconductor company specializing in high-performance analog, RF, and timing solutions before its acquisition by Microchip Technology in 2015. Its legacy timing products remain widely deployed in telecom infrastructure.

The SY69753ALHG belongs to Micrel's Clock and Data Recovery product line, designed specifically for SONET/SDH OC-3/STS-3 applications requiring low-jitter, low-power, and robust lock-holdover performance in industrial environments.

FAQ

What is the primary function of the SY69753ALHG in a SONET OC-3 system?

The SY69753ALHG performs clock recovery and data retiming on 155Mbps NRZ serial data streams in SONET OC-3 systems. It synchronizes an on-chip VCO to the incoming RDIN signal, generating a low-jitter recovered clock (RCLK) and aligned data output (RDOUT) for downstream framer or mapping logic. Its dual-PLL architecture and ±1000ppm tracking window ensure reliable lock under real-world jitter and wander conditions encountered in optical transport networks.

How does the CD (Carrier Detect) pin affect SY69753ALHG operation?

The CD pin on the SY69753ALHG controls recovery enablement: when HIGH, the receiver PLL actively tracks RDIN; when LOW, the SY69753ALHG forces RDOUT and LFIN LOW and locks the PLL to REFCLK instead of RDIN. This behavior provides deterministic fail-safe operation during loss-of-signal events-essential for SONET AIS generation and system-level fault containment without requiring external logic.

What are the key differences between SY69753ALHG and SY87701AL?

SY69753ALHG is a fixed-rate (125/155Mbps), low-power CDR with integrated carrier detect (CD) and SONET-optimized loop response, while SY87701AL is a wide-range AnyRate® CDR (28–1300Mbps) consuming more current and lacking CD input. SY69753ALHG uses simpler loop filter components and offers 30% lower ICC, making it preferable for cost- and power-constrained OC-3 line cards where rate flexibility is unnecessary.

Can SY69753ALHG operate with different reference clock frequencies?

Yes-the SY69753ALHG supports four selectable reference-to-output divide ratios (8×, 10×, 16×, 20×) via TTL inputs DIVSEL1 and DIVSEL2. For example, a 15.625MHz REFCLK yields 125Mbps (8×), while 19.44MHz yields 155.52Mbps (8×). This configurability allows use with common telecom crystal oscillators without requiring custom frequency sources.

What package type and thermal characteristics apply to SY69753ALHG?

SY69753ALHG uses a 32-pin EPAD-TQFP (H32-1) with exposed thermal pad. Its thermal resistance is θJA = 20°C/W at 500lfpm airflow and θJC = 4°C/W, enabling efficient heat dissipation in compact line-card layouts. The package supports Pb-free (NiPdAu) finish and industrial temperature operation (–40°C to +85°C), verified per Micrel's August 2007 datasheet M9999-082107-E.