MAX5988A

MAX5988A/MAX5988B EVALUATION KIT AVAILABLE IEEE 802.3af-Compliant, High-Efficiency, Class 1/Class 2, Powered Devices with Integrated DC-DC Converter General Description The MAX5988A/MAX5988B provide a complete powersupply solution as IEEE® 802.3af-compliant Class 1/ Class 2 Powered Devices (PDs) in a Power-over-Ethernet (PoE) system. The devices integrate the PD interface with an efficient DC-DC converter, offering a low external part count PD solution. The devices also include a low-dropout regulator, MPS, sleep, and ultra-low-power modes. The PD interface provides a detection signature and a Class 1/Class 2 classification signature with a single external resistor. The PD interface also provides an isolation power MOSFET, a 60mA (max) inrush current limit, and a 321mA (typ) operating current limit. The integrated step-down DC-DC converter uses a peak current-mode control scheme and provides an easy-toimplement architecture with a fast transient response. The step-down converter operates in a wide input voltage range from 8.8V to 60V and supports up to 6.49W of input power at 1.3A load. The DC-DC converter operates at a fixed 215kHz switching frequency, with an efficiencyboosting frequency foldback that reduces the switching frequency by half at light loads. The devices feature an input undervoltage-lockout (UVLO) with wide hysteresis and long deglitch time to compensate for twisted-pair cable resistive drop and to assure glitch-free transition during power-on/-off conditio...