Introduction
The PD77728 device is a part of Microchip’s seventh generation IEEE® 802.3bt compliant Power over Ethernet(PoE) Power Sourcing Equipment (PSE) family. This device is a fully integrated 8-port PoE manager with integrated Field Effect Transistor (FET) switches and current sense resistors. Up to 12 devices can be cascaded to provide 48 4-pair ports. The device is available in a 56-pin 8 mm × 8 mm QFN package.

Features
The PD77728 device and PD77728 based PSE have the following key features:
• Supported Standards
– IEEE 802.3bt
• Supported PD Types
– Type 1, Type 2 PDs (802.3af, 802.3at)
– Single-Signature (Type 1–4) PDs
– Dual-Signature (Type 3 and 4) PDs
– Pre-Standard (Legacy) 4-pair PDs
– Supports non-compliant and legacy PDs
• Four Operational Modes
– Controller mode in conjunction with PD77020 PSE Power Management Controller
– Semi-Auto mode
– Managed Auto mode
– Unmanaged Auto mode
• Cascade up to 12 devices to support 96 × 2-pair ports or 48 × 4-pair ports and any 4-pair/2-pair combination
• Device Features
– Stand-Alone device supports up to 8 × 2-pair ports or 4 × 4-pair ports and any 4-pair/2-pair combination
– Per-Port integrated FET, sense resistor, and port diode
– Total port resistance of 160 mΩ
– Device power dissipation ≤ 2W at full load
– Two power rails (55V and 3.3V) for maximum power efficiency
– Guaranteed 4-pair output power of > 90W
– Over Supply Signal (OSS) support
– AutoClass support
– Supports Fast and Perpetual PoE
– MarkHold function support
– Host Interface through I2C Communication
• Real-Time Protection (RTP)
• Measurements
– Per-Port voltage and current measurement
– Accurate main power measurement
• Surge
– Surge up to 2 kV without additional components per IEC61000-4-5-2014
– Surge compliance, ITU-T K.21, GR1089, IE61000-4-5-2014, EN55024
• Up to 10 kV per IEC61000-4-5-2014
• Up to 6 kV per ITU-T K.21
• Physical Characteristics
– Ambient temperature range –40 °C to 85 °C
– 56-pin 8 mm × 8 mm QFN package with thermal pad
– MSL3, RoHS compliant

Applications
The PD77728-based PSE has the following typical applications:
• Campus switches
• Switches and routers for enterprises, small and medium businesses, Small Office Home Office (SOHO), and
commercial markets
• Switches for lighting markets
• PoE injectors