12V/8A有源鉗位正激轉換器、符合IEEE 802.3bt標準的以太網供電（PoE）參考設計

STEVAL-POE005V1

設計簡介

This reference design represents a 12 V, 8 A converter solution ideal for various applications including building safety and security or surveillance, with a PoE-PD interface and a DC-DC active clamp forward converter.

The PoE-PD interface is based on the PM8805 system in package device with two active bridges and an IEEE 802.3bt compliant Powered Device (PD) interface. It can be used in all medium-to-high power 2P and 4P high efficiency PoE and PoE+ applications.
The DC-DC active clamp forward converter is designed around the PM8804 PWM controller, which is an integrated solution for smart and efficient 48?V converters, featuring a programmable oscillator for the switching frequency, adjustable slope compensation, dual complementary low-side drivers with programmable dead time, programmable soft start, soft turn off and a programmable current sense blanking time.

主要特性

Features of the PM8805 PoE-PD interface:
- System in package integrating a double active bridge, a hot-swap MOSFET and a PoE-PD
- Supports legacy high power, 4-pair applications
- 100 V N-ch MOSFETs with 0.2 Ω total path resistance for each active bridge
- Identifies which kind of PSE (standard or legacy) is connected to, and provides successful IEEE802.3 af /at /bt classification indication as combination of the T0, T1 and T2 signals (open drain)
- Smart operational mode selection through the STBY, FAUX and RAUX control signals
- QFN 56 8x8mm package with 43 pins and 6 exposed pads
Features of the PM8804 PWM controller:
- PWM peak current mode controller
- Input operating voltage up to 75 V
- Internal high voltage start up regulator with 20 mA capability
- Programmable fixed frequency up to 1 Mhz
- Soft start up with adjustable time
- Soft turn off (optionally disabled)
- Dual 1?A_PK, low side complementary gate drivers
- GATE2 optionally turned off for reduced consumption
- 80% maximum duty cycle with internal slope compensation
- QFN 16 3x3mm package with exposed pad

參考設計下載

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