BCM84898B0KFSBG: Broadcom 10GBASE-T Ethernet PHY Technical Guide

Introduction

The BCM84898B0KFSBG is a high-performance 10GBASE-T Ethernet PHY transceiver manufactured by Broadcom (now part of Avago Technologies), designed for enterprise switches, routers, network interface cards (NICs), and server connectivity applications requiring 10 Gigabit Ethernet over copper twisted-pair cabling. This single-port PHY supports IEEE 802.3an 10GBASE-T standard, providing full-duplex 10 Gbps data rates over Category 6a/7 copper cables up to 100 meters, with backward compatibility to 1000BASE-T, 100BASE-TX, and 10BASE-T for legacy network infrastructure. This technical guide covers the BCM84898B0KFSBG's key features, detailed specifications, typical applications, and design considerations for network equipment manufacturers.

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Product Overview

What is the BCM84898B0KFSBG?

Part Number Breakdown:

• BCM84898 = Product family (10GBASE-T PHY series)
• B0 = Revision/stepping identifier
• KFSBG = Package code and ordering information

Device Type: Physical Layer (PHY) transceiver IC

Primary Function: Converts digital XGMII/XAUI signals from MAC (Media Access Controller) to analog 10GBASE-T Ethernet signals for transmission over copper cabling

Key Features

1. Multi-Rate Operation:

• 10GBASE-T: 10 Gbps full-duplex (IEEE 802.3an)
• 5GBASE-T: 5 Gbps (NBASE-T, optional depending on variant)
• 2.5GBASE-T: 2.5 Gbps (NBASE-T, optional)
• 1000BASE-T: 1 Gbps (IEEE 802.3ab)
• 100BASE-TX: 100 Mbps (IEEE 802.3u)
• 10BASE-T: 10 Mbps (IEEE 802.3)

2. Interface Support:

• MAC-side: XGMII (10 Gbps), XAUI (4×3.125 Gbps), or reduced XGMII (depending on configuration)
• Line-side: RJ-45 connector via magnetics, supports Cat 6a/7 cabling

3. Power Management:

• IEEE 802.3az Energy Efficient Ethernet (EEE): Reduces power during low traffic periods
• Auto-Negotiation Power Down: Lowers power consumption during link negotiation
• Link-Down Power Saving: Minimal power when no link detected

4. Advanced Features:

• Cable diagnostics (TDR - Time Domain Reflectometry)
• Automatic MDI/MDIX crossover detection
• Comprehensive LED indicators (link, activity, speed)
• Temperature monitoring via internal sensor
• MDIO/MDC management interface (Clause 22/45)

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Technical Specifications

Electrical Characteristics

Parameter	Specification
Data Rates	10M/100M/1G/10G bps
Duplex Mode	Full-duplex (10G), half/full-duplex (10M/100M)
Supply Voltage	1.0V (core), 1.8V/2.5V (I/O), 3.3V (analog)
Power Consumption	~3-4W (10GBASE-T active)
Temperature Range	0°C to +70°C (commercial) / -40°C to +85°C (industrial, if specified)
Package	BGA (Ball Grid Array), typical 484-ball or similar

Interface Specifications

MAC-Side Interface:

• XGMII: 32-bit data path @ 312.5 MHz (10G mode)
• XAUI: 4 differential pairs @ 3.125 Gbps per lane
• GMII/MII: For 1G/100M/10M speeds (backward compatibility)

Line-Side (Copper) Interface:

• Connector: RJ-45 (via external magnetics)
• Cable Support:
  • Category 6a (augmented): 100m @ 10GBASE-T
  • Category 7: 100m @ 10GBASE-T
  • Category 6: 55m @ 10GBASE-T (reduced distance)
  • Category 5e: 1000BASE-T only (not suitable for 10G)

Management Interface:

• MDIO (Management Data I/O): IEEE 802.3 Clause 22 (legacy) and Clause 45 (extended)
• MDC (Management Data Clock): Up to 25 MHz

Performance Specifications

Metric	Value
Latency	<500 ns (typical, 10GBASE-T)
Jitter	<50 ps RMS
BER (Bit Error Rate)	<10⁻¹² (error-free transmission)
Return Loss	>10 dB (IEEE 802.3an compliant)
Insertion Loss	<2 dB @ 100m Cat 6a

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Applications & Use Cases

Application 1: Enterprise Switches

10G Aggregation Switches

Typical Deployment:

• Core/Distribution switches: Uplink ports connecting access layer switches
• Port density: 24/48-port 10GBASE-T switches
• Use case: Data center, campus networks, high-bandwidth aggregation

BCM84898 Integration:

[Switch ASIC] ──XAUI/XGMII── [BCM84898 PHY] ──RJ45── [Cat 6a Cable] ── [Server/Switch]

Benefits:

• Cost-effective 10G over copper (vs SFP+ fiber)
• RJ-45 connector compatibility (existing infrastructure)
• Power over Ethernet (PoE++) capability (with additional circuitry)

Application 2: Network Interface Cards (NICs)

Server 10G NICs

Configuration:

• Single-port or dual-port 10GBASE-T NICs
• PCIe x8/x16 host interface
• RJ-45 connectors for direct server-to-switch connectivity

BCM84898 Integration:

[Server PCIe] ── [NIC Controller] ──XGMII── [BCM84898] ── RJ45 ── Switch

Advantages:

• No fiber transceivers needed (lower cost)
• Backward compatible with 1GbE switches
• Cable management simplicity

Application 3: Routers

Enterprise/Carrier Routers

Use Cases:

• WAN aggregation routers
• Branch office routers with 10G uplinks
• Carrier-grade CPE (Customer Premises Equipment)

BCM84898 Role:

• Provides 10G copper uplink interface
• Connects to fiber aggregation switches via media converters
• Enables high-speed branch-to-datacenter connectivity

Application 4: Storage Networks

NAS/SAN Connectivity

Applications:

• Network Attached Storage (NAS) 10G ports
• Storage Area Network (SAN) copper connectivity
• Backup/replication traffic (high bandwidth)

Performance:

• 10 Gbps sustained throughput
• Low latency (<500 ns) critical for storage I/O
• Supports jumbo frames (9K MTU)

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Design Considerations

PCB Layout Guidelines

Critical Design Aspects:

1. Power Supply Decoupling:

- Place 0.1µF ceramic capacitors close to each power pin
- Add 10µF bulk capacitors per power rail
- Separate analog (3.3V) and digital (1.0V/1.8V) power planes

2. High-Speed Signal Routing:

• XGMII/XAUI differential pairs:
  • Impedance: 100Ω differential
  • Length matching: ±5 mils within pair, ±50 mils between pairs
  • Avoid vias if possible; if needed, use back-drilling
• MDI (RJ-45 signals):
  • Route as differential pairs (100Ω)
  • Minimize trace length to magnetics (<1 inch ideal)

3. Thermal Management:

• Power dissipation: 3-4W typical @ 10GBASE-T
• Cooling: Heatsink or thermal pad recommended
• PCB: 4-layer minimum (6-layer preferred for signal integrity)
• Thermal vias: Place under package for heat transfer to ground plane

4. Magnetics Selection:

• Pulse Electronics: H5025NLT (10GBASE-T magnetics with integrated termination)
• Wurth Elektronik: 7499210121 (10G Ethernet transformer module)
• Bourns: SM51630EL (10GBASE-T single-port magnetics)

Software/Firmware Considerations

PHY Configuration via MDIO:

Typical Initialization Sequence:

1. Reset PHY (MDIO write to control register)
2. Configure speed/duplex (auto-negotiation enable or force mode)
3. Enable EEE (if power saving required)
4. Configure LEDs (link, activity, speed indicators)
5. Set loopback modes (for testing, if needed)

Register Access Example (Clause 45):

// Read PHY ID Register
MDIO_READ(PHY_ADDR, DEVAD=1, REG=2) → Returns OUI (Broadcom ID)

// Enable Auto-Negotiation
MDIO_WRITE(PHY_ADDR, DEVAD=7, REG=0, VALUE=0x1200)

Driver Support:

• Linux kernel drivers: Broadcom PHY driver (bcm84881.c or similar)
• Custom firmware: MDIO register access via I2C/SPI-to-MDIO bridge

Compliance & Testing

Required Certifications:

1. IEEE 802.3 Compliance:

• 10GBASE-T interoperability testing
• Cable compliance (Cat 6a/7 certification)

2. Electromagnetic Compatibility (EMC):

• FCC Part 15 Class A/B (radiated emissions)
• EN 55032 (European EMC directive)

3. Safety:

• UL/cUL certification (if applicable)
• CE marking (European Economic Area)

Test Equipment:

• BERT (Bit Error Rate Tester): Anritsu, Keysight
• Cable certifier: Fluke DSX-5000 (Cat 6a certification)
• Oscilloscope: ≥20 GHz bandwidth for eye diagram analysis

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Comparison with Alternatives

BCM84898 vs Competing 10GBASE-T PHYs

Feature	BCM84898 (Broadcom)	Marvell 88E2110	Aquantia AQR107
Data Rates	10M/100M/1G/10G	10M/100M/1G/10G	100M/1G/2.5G/5G/10G
NBASE-T Support	Limited	No	Yes (2.5G/5G)
Power Consumption	3-4W	3.5W	2.5W (lower)
EEE Support	Yes	Yes	Yes
Package	BGA	BGA	BGA
Typical Use	Enterprise switches	NAS, switches	Consumer routers, gaming

BCM84898 Advantages:

• Proven enterprise-grade reliability (Broadcom reputation)
• Wide adoption in tier-1 networking equipment (Cisco, HP, Dell)
• Comprehensive cable diagnostics

Aquantia AQR107 Advantage:

• Lower power consumption (important for multi-port switches)
• Native NBASE-T support (2.5G/5G for Wi-Fi 6/6E access points)

Conclusion

The BCM84898B0KFSBG from Broadcom is a high-performance, enterprise-grade 10GBASE-T Ethernet PHY transceiver enabling 10 Gigabit connectivity over standard copper cabling in switches, NICs, routers, and storage networks. With support for multi-rate operation (10M/100M/1G/10G), IEEE 802.3az Energy Efficient Ethernet, comprehensive cable diagnostics, and proven reliability in tier-1 networking equipment, the BCM84898B0KFSBG provides an ideal solution for network equipment manufacturers requiring cost-effective 10G copper connectivity with backward compatibility to legacy Gigabit Ethernet infrastructure.

Key Takeaways:

✅ 10GBASE-T PHY: 10 Gbps over Cat 6a/7 copper (100m)
✅ Multi-rate: Backward compatible to 1G/100M/10M
✅ Interfaces: XGMII/XAUI (MAC-side), RJ-45 (line-side)
✅ Power: 3-4W with IEEE 802.3az EEE support
✅ Applications: Enterprise switches, server NICs, routers
✅ Features: Auto-negotiation, cable diagnostics, MDI/MDIX
✅ Design: Requires careful PCB layout, magnetics, thermal management

Sourcing BCM84898B0KFSBG or need design support? Visit AiChipLink.com for availability, pricing, and technical consultation for 10GBASE-T PHY integration.

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Written by Jack Elliott from AIChipLink.

 

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