SY87729LHY - 365MHz Fractional-N Clock Synthesizer | Microchip
料号： SY87729LHY ✓ 量产中SY87729LHY 概述
A fractional-N synthesizer is a clock and timing IC that synthesizes programmable frequencies from a stable reference. Its hierarchy is fractional-N synthesizer > PLL-based clock generator > clock synthesizer > clock and timing IC > semiconductor. This technology is particularly useful when a system needs a precise communications reference without relying on a separate crystal oscillator for every output frequency. Differential PECL outputs provide complementary signals suited to high-speed digital clocking and optical-transponder systems.
The SY87729LHY operates from a 3.3V supply and synthesizes frequencies from 10MHz to 365MHz using a single reference source. The verified search material specifically describes a 27MHz reference input and a maximum output of 365MHz. It generates the correct differential PECL reference required by the Micrel SY87721L combined clock-and-data-recovery and clock-multiplier-unit device, whose associated data rate range extends from 10Mbps to 2.7Gbps.
Fractional-N synthesis permits accurate generation of transport-related reference frequencies with or without forward-error correction. This is valuable in systems requiring standards-compliant downstream data units even when the associated upstream interface produces no signal. Exact phase-noise, jitter, reference-input, output-frequency, and divider specifications are not included in the supplied excerpts and must be confirmed in the manufacturer datasheet before final timing-budget approval.
Typical uses include optical transponders, SONET-compatible transport equipment, Ethernet-compatible clocking systems, and other communications links driven by the SY87721L. In these applications, the synthesizer establishes the local reference required by the downstream CDR/CMU, while the 365MHz upper output range provides headroom for demanding clock rates. Board-level signal integrity and differential clock routing remain essential because high-speed edge quality is not determined by output frequency alone.
Designers should place the input, output, and bypass connections as shown in the manufacturer application guidance, maintain short return paths, and use controlled-impedance routing for differential PECL pairs. The exposed pad should be connected to the ground plane according to the datasheet thermal and layout instructions. Because detailed termination and decoupling values were not supplied here, those values must be taken directly from the SY87729L manufacturer datasheet rather than inferred.
This product summary combines verified manufacturer and distributor information, pricing available as of 2026-10-28, same-family replacement information, and practical guidance for evaluating the SY87729LHY. It highlights where verified data is complete and marks unresolved electrical, environmental, pin-level, and lifecycle details rather than presenting unsupported assumptions as specifications.
直接替换替代料： SY87729LHY ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
本系列中的变体
可与以下型号直接替换的同系列型号： SY87729LHY （相同外形与封装尺寸） ——差异在于 Package.
SY87729LHI
✅ 直接替换联系询价
SY87729LHY 规格参数
| Device Type | Fractional-N frequency synthesizer and clock synthesizer |
| 电源电压 | 3.3 V |
| Supply Voltage Range | 3.15 V to 3.45 V |
| Output Frequency Range | 10 MHz to 365 MHz |
| Reference Input Frequency | 27 MHz |
| Output Logic | Differential PECL |
| Architecture | Rate-independent fractional-N synthesizer |
| 引脚数 | 32 pins |
| 封装 | 32-pin TQFP with exposed pad |
| 安装类型 | Surface mount |
| Compatible Clock and Data Recovery Device | SY87721L |
| Associated Data Rate Range | 10 Mbps to 2.7 Gbps |
| RoHS Compliance | unknown |
| REACH Compliance | unknown |
| AEC-Q100 Qualification | not_applicable |
SY87729LHY 32-pin tqfp with exposed pad 引脚配置指南
SY87729LHY（32-pin tqfp with exposed pad 封装）的引脚配置。 引脚编号、功能和连接图在制造商数据手册中定义。请参阅该手册以了解确切的封装尺寸和焊接指南。
暂无详细引脚数据： SY87729LHY.
请参阅 数据手册 以查看完整引脚配置。
典型应用
SY87729LHY 适用于 6 应用s: Optical Transponder Timing, SONET-Compatible Transport Systems, Ethernet-Compatible Clocking, High-Speed Backplane Clocking, Clock Multiplier and CDR Support, Instrumentation Clock Reference.
Optical Transponder Timing
The SY87729LHY fits optical transponder timing because it generates an exactly correct reference for standards-compliant downstream protocol data units, even when the upstream interface produces no signal. Its fractional-N architecture uses a 27MHz reference to produce differential PECL outputs across 10MHz to 365MHz. This is useful where the transponder must maintain a valid local reference independent of incoming traffic. The principal design check is the complete communications timing budget, including reference jitter, PECL termination, and the exact protocol frequency required by the associated CDR/CMU.
推荐
SONET-Compatible Transport Systems
The SY87729LHY is suitable for transport-clock subsystems that require a programmable, standards-compliant reference derived from one oscillator. Its 3.3V operation and 10MHz-to-365MHz synthesis range cover the clocking role described for the SY87721L in communications equipment. Using one synthesized differential PECL reference can simplify clock distribution compared with maintaining multiple unrelated oscillators. Designers must still verify the required transport rate, jitter contribution, reference accuracy, and whether forward-error correction changes the synthesized frequency requirement.
推荐
Ethernet-Compatible Clocking
The SY87729LHY can provide the differential reference clock required by communications clocking chains based on the SY87721L. Its fractional-N synthesis supports exact generation of transport-related frequencies from a single 27MHz source, while the 365MHz maximum output provides substantial range for high-rate designs. In an Ethernet-oriented subsystem, the device may simplify the relationship between an external reference and a downstream CDR/CMU. Before deployment, verify the required line rate, recovery range, jitter budget, and implementation standards supported by the complete transceiver architecture.
推荐
High-Speed Backplane Clocking
The SY87729LHY is applicable where a board requires a locally generated differential PECL reference for high-speed digital timing. A 27MHz reference can be synthesized into outputs spanning 10MHz to 365MHz, providing flexibility across multiple communication modes within the same design. Differential routing helps correlate the two clock edges when the receiver is appropriately terminated and the PCB meets impedance requirements. The design must account for insertion loss, skew between the differential pair, return loss, and reference-jitter accumulation; those detailed values were not present in the supplied excerpts.
推荐
Clock Multiplier and CDR Support
The SY87729LHY was designed to generate the reference frequency used by the SY87721L combined clock-and-data-recovery and clock-multiplier-unit device. That relationship makes it suitable for systems operating from 10Mbps to 2.7Gbps when the downstream architecture uses this Micrel timing chain. The synthesizer separates reference generation from clock multiplication and recovery, allowing the reference to remain correct even during upstream signal absence. Board-level validation should confirm lock range, loop bandwidth, jitter transfer, and startup behavior for the selected SY87721L configuration.
推荐
Instrumentation Clock Reference
The SY87729LHY can serve as a programmable clock source in laboratory or industrial instrumentation that requires multiple derived frequencies from a common 27MHz reference. Its 10MHz-to-365MHz fractional-N output range provides flexibility for driving compatible timing and communications blocks, while the differential PECL interface can offer useful noise and edge behavior on a controlled board. The principal limitations are that exact output-divider settings, channel configuration, jitter, and output-drive specifications must be taken from the manufacturer datasheet rather than inferred from the output-frequency range.
推荐
推荐产品汇总
工程参考数据： SY87729LHY ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | SY87729LHI |
|---|---|---|
| Package | 32-pin TQFP with exposed pad | TQFP - same package and terminal compatibility |
| Brand | Microchip Technology | Microchip Technology |
| Device Function | 3.3V fractional-N frequency synthesizer | Fractional-N clock synthesizer with consistent main performance characteristics |
| Drop-In Compatibility | Primary ordering target | Compatible according to supplied cross-reference evidence |
关键差异点
- Integrated fractional-N synthesis for communications references （对比 SY87729LHI)
- Exact reference generation during upstream signal absence （对比 SY87729LHI)
- Broad synthesized output range from one reference （对比 SY87729LHI)
设计说明
Route each differential PECL output as a tightly coupled impedance-controlled pair with a continuous reference plane beneath it. Minimize stubs, vias, and unnecessary branch loads because discontinuities can degrade edge quality and return loss. The supplied sources do not specify the required characteristic impedance, so the PCB stackup and interface standard must be established from the manufacturer datasheet and receiver requirements rather than assumed.
Follow the manufacturer’s recommended supply decoupling and exposed-pad grounding arrangement. The verified operating range is 3.15V to 3.45V, so routing and transient margins should be evaluated across that full range rather than only at nominal 3.3V. Place bypass capacitors close to the supply pins and provide a low-impedance ground return to control supply noise, although exact capacitance values are not present in the supplied excerpts.
Build a complete jitter budget that includes the 27MHz reference, the fractional-N synthesizer, the SY87721L clock-and-data-recovery path, and the downstream receiver. Verify differential skew and termination against the complete communications system because a 365MHz output capability alone does not guarantee compliance with a specific protocol. Request the manufacturer’s phase-noise and output-jitter curves before defining the final timing margin.
Do not treat SY87729LHY-TR as a distinct functional upgrade merely because it appears in cross-reference results; the supplied evidence indicates the same core device with a different ordering or shipping configuration. Likewise, do not assume SY87729LHI is qualified for every SY87729LHY application without checking temperature grade, screening, and approved-part requirements. These suffix distinctions can affect procurement even when the footprint is unchanged.
合规信息
The supplied verified web excerpts do not state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status. The SY87729L is a communications clock-generation IC rather than an automotive-qualified device, so AEC-Q100 is marked not applicable; all other unsupported compliance claims remain unknown.
