MAX5935 + max5940 + max5014 : A Power Over Ethernet solution
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Maxim Integrated Products introduces a Power Over Ethernet solution based on MAX5935 + MAX5940 + MAX5014.
PSE Side, POE Controller
The MAX5935 quad network power controller is designed for use in IEEE 802.3af-compliant power sourcing equipment (PSE). The device provides power devices (PD) discovery, classification, current limit, and both DC and AC load disconnect detections. The MAX5935 can be used in either endpoint PSE (LAN switches/routers) or midspan PSE (power injector) applications.
The MAX5935 can operate autonomously or be controlled by software through an I2C-compatible interface. Separate input and output data lines (SDAIN and SDAOUT) allow usage with optocouplers. The MAX5935 is a slave device. Its four address inputs allow 16 unique MAX5935 addresses. A separate active-low INT output and four independent shutdown inputs (active-low SHD_) allow fast response from a fault to port shutdown. A active-low RESET input allows hardware reset of the device. A special Watchdog feature allows the hardware to gracefully take over control if the software crashes. A cadence timing feature allows the MAX5935 to be used in midspan systems.
The MAX5935 is fully software configurable and programmable. A class-over-current detection function enables system power management to detect if a PD draws more current than the allowable amount for its class. Other features are input under/overvoltage lockout, overtemperature protection, output voltage slew-rate limit during startup, power-good, and fault status. The MAX5935's programmability includes gate charging current, current-limit threshold, startup timeout, overcurrent timeout, autorestart duty cycle, PD disconnect AC detection threshold, and PD disconnect detection timeout.
The MAX5935 is available in a 36-pin SSOP package and is rated for both extended (-40°C to +85°C) and commercial (0°C to +70°C) temperature ranges.
PD Side, POE Controller + DC/DC Converter
The MAX5940A/MAX5940B/MAX5940C/MAX5940D provide complete interface function for a powered device (PD) to comply with the IEEE® 802.3af standard in a power-over-ethernet system. MAX5940A/MAX5940B/MAX5940C/MAX5940D provide the PD with a detection signature, a classification signature, and an integrated isolation switch with programmable inrush current control. These devices also feature power-mode undervoltage lockout (UVLO) with wide hysteresis and power-good outputs. The MAX5940A/MAX5940B are available with an absolute maximum rating of 80V and the MAX5940C/MAX5940D are rated for an absolute maximum rating of 90V.
An integrated MOSFET provides PD isolation during detection and classification. All devices guarantee a leakage current offset of less than 10µA during the detection phase. A programmable current limit prevents high inrush current during power-on. The device features power-mode UVLO with wide hysteresis and long deglitch time to compensate for twisted-pair cable resistive drop and to assure glitch-free transition between detection, classification, and power-on/-off phases.
The MAX5940A/MAX5940C provide an active-high (PGOOD) open-drain output and a fixed UVLO threshold. The MAX5940B/MAX5940D provide both active-high (PGOOD) and active-low (active-low PGOOD) outputs and have an adjustable UVLO threshold with the default value compliant to the 802.3af standard. All devices are designed to work with or without an external diode bridge.
The MAX5940A/MAX5940B/MAX5940C/MAX5940D are available in 8-pin SO packages and are rated over the extended temperature range of -40°C to +85°C.
The MAX5014/MAX5015 integrate all the building blocks necessary for implementing DC-DC fixed-frequency isolated power supplies. These devices are current-mode controllers with an integrated high-voltage startup circuit suitable for isolated telecom/industrial voltage range power supplies. Current-mode control with leading-edge blanking simplifies control-loop design and internal ramp compensation circuitry stabilizes the current loop when operating at duty cycles above 50% (MAX5014). The MAX5014 allows 85% operating duty cycle and could be used to implement flyback converters, whereas the MAX5015 limits the operating duty cycle to less than 50% and can be used in single-ended forward converters. A high-voltage startup circuit allows these devices to draw power directly from the 18V to 110V input supply during startup. The switching frequency is internally trimmed to 275kHz ±10%, thus reducing magnetics and filter component costs.
The MAX5014/MAX5015 are available in 8-pin SO packages. An evaluation kit (MAX5015EVKIT) is also available.