LINEAR TECHNOLOGY LTC4257 User Guide
Summary
The LTC4257 is a professional interface controller designed for managing Power over Ethernet (PoE) connections according to the IEEE 802.3af standard. It offers comprehensive PD compatibility, handling signature detection, programmability of classification currents (Class 0-4), and system power good signaling within a single chip. This manual serves as a detailed resource for system designers building reliable Power Sourcing Equipment (PSE) solutions, including IP phones and wireless access points (WAPs). It provides full electrical specifications, application guidelines, and package options necessary for robust, cost-effective PoE management.
Manual Details
| Brand | Linear |
|---|---|
| Pages | 20 |
| File Size | 254.63 KB |
| Published | July 15, 2026 |
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Frequently Asked Questions
What is the LTC4257 designed to interface with?
It provides complete functions for signature and power Powered Devices (PDs) operating in an IEEE 802.3af PoE system.
What types of package options are available for the LTC4257?
It is available in 8-pin SO and low profile 3mm × 3mm DFN packages.
How does the unit protect against power issues?
It includes programmable classification current with thermal foldback, undervoltage lockout, and a Power Good signal onboard.
What temperature range is available for the LTC4257 in specific grades?
The 'I' grade variant operates from -40°C to 85°C, while the standard 'C' grade is rated for 0°C to 70°C.