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The MAX5987AETE+T is a Power over Ethernet (PoE) PD interface controller with integrated switching regulator from Maxim Integrated (now part of Analog Devices).

Key Specifications:

• Manufacturer: Maxim Integrated (Analog Devices)
• Part Number: MAX5987AETE+T
• Package: 16-TQFN (3x3mm)
• Input Voltage Range (PoE): 36V to 57V (IEEE 802.3af/at compliant)
• Output Voltage: Adjustable (via external resistor)
• Integrated Switching Regulator: Yes (DC-DC converter)
• IEEE 802.3af/at Compliance: Yes
• Detection & Classification: Supports PD detection and classification
• Operating Temperature Range: -40°C to +85°C
• Efficiency: Up to 90%
• Protection Features: Overcurrent, overtemperature, undervoltage lockout (UVLO)

Features:

• Single-chip IEEE 802.3af/at compliant PD interface
• Integrated switching regulator for high efficiency
• Programmable output voltage
• Supports both 2-event and 4-event classification
• Thermal shutdown protection
• Low-power dissipation
• RoHS compliant

This device is designed for PoE-powered devices (PDs) such as IP cameras, wireless access points, and VoIP phones.

# MAX5987AETE+T: Power over Ethernet (PoE) PD Controller

## Practical Application Scenarios

The MAX5987AETE+T from Maxim Integrated is a highly integrated Power over Ethernet (PoE) Powered Device (PD) controller designed for IEEE 802.3af/at compliance. Its primary applications include:

1. IP Cameras and Surveillance Systems

The MAX5987AETE+T efficiently manages power delivery in PoE-enabled IP cameras, eliminating the need for separate power supplies. Its wide input voltage range (36V to 57V) and robust thermal performance make it ideal for outdoor deployments.

2. Wireless Access Points (WAPs) and IoT Devices

The controller supports both low-power (802.3af, 12.95W) and high-power (802.3at, 25.5W) modes, enabling flexible deployment in Wi-Fi routers, sensors, and smart building systems.

3. VoIP Phones and Industrial Equipment

With built-in detection, classification, and undervoltage lockout (UVLO), the MAX5987AETE+T ensures reliable power negotiation in mission-critical applications like VoIP handsets and factory automation controllers.

4. Medical and Portable Devices

The IC’s low quiescent current and compact TQFN package suit battery-backed or PoE-powered medical monitors, where space and efficiency are critical.

## Common Design-Phase Pitfalls and Avoidance Strategies

1. Inadequate Thermal Management

*Pitfall:* High-power PoE applications can cause excessive heat dissipation, leading to premature failure.

*Solution:* Ensure proper PCB layout with thermal vias and a copper pour under the IC. Use external MOSFETs with low RDS(ON) to minimize power losses.

2. Incorrect Signature Resistor Selection

*Pitfall:* Non-compliant signature resistors (e.g., outside 24.9kΩ ±1%) may cause the Power Sourcing Equipment (PSE) to reject the PD.

*Solution:* Use precision resistors and verify compliance with IEEE 802.3af/at standards during prototyping.

3. Poor EMI Performance

*Pitfall:* Radiated emissions from switching circuits can disrupt nearby sensitive electronics.

*Solution:* Implement proper filtering (e.g., ferrite beads, LC filters) and follow Maxim’s layout guidelines for minimizing loop areas.

4. Faulty Classification

*Pitfall:* Incorrect class setting (e.g., Class 0 vs. Class 4) may lead to insufficient power allocation.

*Solution:* Configure the CLASS pin correctly and validate power negotiation using a PSE tester.

## Key Technical Considerations for Implementation

1. Input Voltage Range

The MAX5987AETE+T operates from 36V to 57V, accommodating both 802.3af (44V–57V) and 802.3at (50V–57V) voltage ranges. Ensure the input withstands transients up to 80V.

2. External MOSFET Selection

Choose MOSFETs with low gate charge (Qg) and RDS(ON) to optimize efficiency. A 100V-rated MOSFET is recommended for margin.

3. Isolation Requirements