PI6C557-03AQE - PCIe 2.0 Spread Spectrum Clock Generator | Diodes Inc
料号： PI6C557-03AQE ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $1.42 | $1.42 |
| 10 | $1.28 | $12.80 |
| 100 | $1.04 | $104.00 |
| 500 | $0.86 | $430.00 |
| 1,000 | $0.74 | $740.00 |
PI6C557-03AQE 概述
A spread-spectrum clock generator is a timing device that intentionally modulates the output frequency around a center value at a low modulation rate. By spreading the spectral energy of the clock over a wider bandwidth, peak EMI emissions are reduced, helping designs pass regulatory compliance tests such as FCC Class B and CISPR 22. Within the broader clock-and-timing IC category, this part sits in the PCIe clock-generator subcategory alongside PLLs, frequency synthesizers, and zero-delay buffers.
Key features include a 25 MHz crystal input, two HCSL (current-mode differential) output pairs, on-chip termination support, output enable / power-down control, and selectable spread-spectrum depth. HCSL is the signaling standard required by PCIe 2.0/3.0 reference clocks and is also used in mainstream Ethernet PHYs. The internal PLL is sourced from Pericom's spread-spectrum technology and maintains low cycle-to-cycle jitter even with active modulation.
Typical applications include PCIe add-in cards (network, storage, graphics), embedded systems needing EMI-controlled 100 MHz reference clocks, Ethernet switches and NIC reference rails, and industrial PCs where the part's compliance footprint helps shorten EMI qualification cycles. The device's small 16-QSOP footprint is suitable for compact motherboard layouts.
When designing with the PI6C557-03AQE, follow PCIe CEM routing guidelines for the HCSL outputs - 85 ohm differential traces, AC coupling capacitors at the receiver, and length matching within the PCIe spec. The 25 MHz crystal must be fundamental-mode with a load capacitance appropriate for the on-chip oscillator.
直接替换替代料： PI6C557-03AQE ——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： PI6C557-03AQE （相同外形与封装尺寸） ——差异在于 Number of Outputs, Package, Function, Output Type, Number of Inputs.
快速对比工具——选择替代料号进行并排对比：
PI6C557-03AQEX
✅ 直接替换📋 参考替代料（不在目录中）
PI6C557-03ALEX
✅ 直接替换📋 参考替代料（不在目录中）
PI6C557-03BLE
✅ 直接替换📋 参考替代料（不在目录中）
PI6C557-03AQE 最大额定值与电气特性
| Product Type | Spread-Spectrum Clock Generator |
| 功能 | PCI Express / Ethernet reference clock generator |
| Input Reference | 25 MHz fundamental-mode crystal |
| Output Frequency Options | 25 / 100 / 125 / 200 MHz (selectable) |
| 输出数量 | 2 differential pairs (4 signals) |
| 输出类型 | HCSL (current-mode differential) |
| 电源电压 | 3.3 V (3.0 V to 3.6 V range) |
| PCIe Compliance | PCI Express 2.0 reference clock |
| Spread Spectrum | Selectable spread depth |
| 工作温度 | -40 C to +85 C (industrial) |
| 封装 | 16-QSOP (also listed as 16-SSOP) |
PI6C557-03AQE 引脚配置
| 引脚 1 | VDD — 3.3 V power supply |
| 引脚 2 | GND — Ground reference |
| 引脚 3 | X1 — 25 MHz crystal input 1 |
| 引脚 4 | X2 — 25 MHz crystal input 2 |
| 引脚 5 | OE — Output enable (active per datasheet) |
| 引脚 6 | S0 — Frequency select input 0 |
| 引脚 7 | S1 — Frequency select input 1 |
| 引脚 8 | GND — Ground reference |
| 引脚 9 | Q0 — HCSL output 0 (positive) |
| 引脚 10 | Q0# — HCSL output 0 (negative) |
| 引脚 11 | VDD — 3.3 V power supply (output) |
| 引脚 12 | GND — Ground reference |
| 引脚 13 | Q1 — HCSL output 1 (positive) |
| 引脚 14 | Q1# — HCSL output 1 (negative) |
| 引脚 15 | NC — Not connected (per datasheet) |
| 引脚 16 | VDD — 3.3 V power supply |
典型应用
PI6C557-03AQE 适用于 6 应用s: PCIe Add-in Card Reference Clock, Embedded System Reference Clock, Ethernet Switch / NIC Reference, Storage Controller Clock Tree, Industrial PC Motherboard, Set-Top Box / Consumer Electronics.
PCIe Add-in Card Reference Clock
The PI6C557-03AQE supplies the 100 MHz HCSL reference clock that every PCIe Gen 2 endpoint (NIC, SSD controller, GPU) requires for link training and serializer-deserializer operation. With two HCSL output pairs from one 25 MHz crystal, this Diodes device is ideal for add-in cards that drive both a local endpoint and a downstream slot. Its spread-spectrum modulation reduces conducted and radiated EMI by 7-12 dB on 100 MHz harmonics, easing FCC Class B qualification for consumer NICs and graphics cards. The 16-QSOP footprint fits compact card layouts.
推荐
Embedded System Reference Clock
Embedded boards needing an EMI-controlled 100 MHz PCIe reference clock for onboard devices (Ethernet PHY, SATA controller, M.2 slot) benefit from the PI6C557-03AQE's small footprint and spread-spectrum output. The part's 3.3 V supply is compatible with standard industrial SBC rails, and its -40 C to +85 C industrial temperature rating supports factory-floor installations. Pairing it with a 25 MHz crystal oscillator on the same board avoids the need for an external clock generator chip, simplifying BOM and shrinking PCB area in industrial PCs and IoT gateways.
推荐
Ethernet Switch / NIC Reference
Gigabit Ethernet PHYs and 10/100/1000 switches commonly require 25 MHz or 125 MHz reference clocks. The PI6C557-03AQE provides both HCSL pairs from a single 25 MHz crystal, with the 125 MHz output suited to many Ethernet PHY reference inputs and the 100 MHz pair serving downstream PCIe devices. Spread-spectrum frequency modulation is particularly valuable in multi-port enterprise switches where FCC/CE compliance at high port densities is challenging. Pin compatibility within the Diodes PI6C557-03A family allows seamless migration across products.
推荐
Storage Controller Clock Tree
NVMe SSDs, SAS/SATA controllers, and RAID HBAs each require a clean 100 MHz PCIe reference clock. The PI6C557-03AQE with its two HCSL pairs can feed both a host PCIe Gen 2 endpoint PHY and a downstream port expander, simplifying the storage controller board clock tree. Spread-spectrum modulation helps SSDs in densely packed enterprise arrays pass EMI limits without extensive shielding. The 16-QSOP industrial-grade package supports the wide temperature ranges required by data-center storage enclosures.
推荐
Industrial PC Motherboard
Industrial motherboards need a reliable PCIe reference clock for multiple add-in slots while keeping EMI emissions within industrial certification limits (EN 55022, FCC Part 15). The PI6C557-03AQE's two HCSL outputs can fan out to two PCIe Gen 2 slots from a single 25 MHz crystal, and its spread-spectrum output eases the burden on motherboard-level EMI shielding. The 16-QSOP package is compatible with automated SMT assembly lines used in industrial PC production. The same Diodes part serves Fanless industrial designs where thermal and EMI margins are tight.
推荐
Set-Top Box / Consumer Electronics
Consumer set-top boxes and HDMI-enabled media gateways integrate Ethernet and PCIe interfaces that require a 100 MHz PCIe reference clock. The PI6C557-03AQE provides two HCSL pairs from a single 25 MHz reference, allowing the same clock source to feed both the Ethernet PHY and the HDMI bridge chip. Spread-spectrum modulation is critical in CE-marked consumer devices, where rigid FCC Class B / EN 55022 limits apply. The small 16-QSOP footprint keeps BOM cost low in cost-sensitive consumer applications.
推荐
推荐产品汇总
工程参考数据： PI6C557-03AQE ——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 | PI6C557-03AQEX | PI6C557-03ALEX | PI6C557-03BLE |
|---|---|---|---|---|
| Brand | Diodes Incorporated | Diodes Incorporated | Diodes Incorporated | Diodes Incorporated |
| Package | 16-QSOP | 16-QSOP - same | 16-QSOP - same | 16-QSOP - same |
| PCIe Generation | PCIe 2.0 | PCIe 2.0 | PCIe 2.0 | PCIe 2.0 |
| Output Frequencies | 25/100/125/200 MHz | 25/100/125/200 MHz | 25/100/125/200 MHz | 25/100/125/200 MHz |
| Output Signaling | HCSL x2 pairs | HCSL x2 pairs | HCSL x2 pairs | HCSL x2 pairs |
| Supply Voltage | 3.3 V | 3.3 V | 3.3 V | 3.3 V |
| Spread Spectrum | Selectable | Selectable | Selectable | Selectable |
| Crystal Reference | 25 MHz fundamental | 25 MHz fundamental | 25 MHz fundamental | 25 MHz fundamental |
关键差异点
- Pin-to-pin drop-in within the PI6C557-03A family （对比 PI6C557-03AQEX / PI6C557-03ALEX / PI6C557-03BLE)
- Two HCSL differential outputs from one 25 MHz crystal （对比 Single-output clock generators)
- On-chip spread spectrum for EMI reduction （对比 Non-spread-spectrum 100 MHz clock generators)
设计说明
Follow PCI Express CEM routing guidelines for the 100 MHz HCSL outputs: use 85 ohm differential impedance, place AC-coupling capacitors at the receiver (within 200 mils of the receiver pin), and match intra-pair length to within 5 mils. Keep the 25 MHz crystal traces short and symmetric to the X1/X2 pins, with the crystal load capacitors placed within 50 mils. Avoid routing the HCSL outputs across any split-plane or non-continuous reference plane, which increases radiated EMI and can break PCIe link training.
Do not omit the output enable (OE) pull-up/down resistor when unused - if left floating, the HCSL outputs may be in an undefined state and produce unwanted clock activity at power-up, confusing PCIe link training. Select S0/S1 frequency-select inputs via logic-level CMOS signals; they must not be left floating. Verify the 25 MHz crystal's load capacitance rating (typically 18 pF or 20 pF) against the on-chip oscillator specification; mismatch reduces the effective pull range by tens of ppm and may violate PCIe Gen 2 ppm requirements.
Spread-spectrum modulation on the 100 MHz HCSL output typically reduces peak EMI by 7-12 dB depending on spread depth selection. Re-measure conducted and radiated emissions after PCB layout changes; spread depth above -0.5% may exceed the PCIe CEM spec for some receivers and must be validated. Pair the PI6C557-03AQE with a low-ESR decoupling capacitor (0.1 uF X7R) within 100 mils of each VDD pin to minimize supply-borne jitter. If the design is EMC-sensitive (industrial, automotive), consider shielding the clock section and using ferrite beads on the 3.3 V supply rail.
合规信息
RoHS compliant per Diodes Inc product family documentation. Industrial temperature grade -40 C to +85 C. Not AEC-Q100 qualified; choose an automotive-grade spread-spectrum clock generator for vehicle applications.
