PM8800A STMicroelectronics

PM8800A Integrated IEEE 802.3af compliant PoE-PD interface and PWM controller with support of external source Features IEEE 802.3af compliant PD interface Works with power supplied from Ethernet LAN cables or from local auxiliary sources Integrated 100 V, 0.5 , 800 mA hot-swap HTSSOP16 MOSFET Integrated signature resistor Description Programmable in-rush current limit The PM8800A integrates a standard power over Programmable classification current Ethernet (PoE) interface and a current mode Programmable DC current limit up to 800 mA PWM controller to simplify the design of the High voltage start-up bias regulator power supply sections of all powered devices. Thermal shutdown protection The PoE interface incorporates all the functions required by the IEEE 802.3af including detection, Current mode pulse width modulator classification, under-voltage lockout (UVLO) and Programmable oscillator frequency in-rush current limitation. Programmable soft-start PM8800A specifically targets PD with extended Power good indication power requirement with respect to the limit 80 % maximum duty cycle with internal slope imposed by the 802.3af standard, embedding a compensation hot-swap MOSFET capable of sustaining twice the current of the 802.3af standard with a Supports both isolated and non-isolated programmable DC current limit. Applications. The integrated switching regulator has been HTSSOP16 package designed to work with power either form the Ethernet cable connection or from an external Applications power source such as AC adapter. VoIP phones, WLAN access points The DC-DC section of the PM8800A features a programmable oscillator frequency, soft-start, Security cameras slope compensation and embeds a voltage output PoE powered device appliances error amplifier allowing use in both isolated and High power (>12.95 W) powered devices non isolated configuration. Table 1. Device summary Order codes Package Packing PM8800A HTSSOP16 Tube PM8800ATR HTSSOP16 Tape and reel February 2008 Rev 2 1/35 www.st.com 35Contents PM8800A Contents 1 Typical application circuit and block diagram 4 1.1 Application circuits . 4 1.2 Block diagram . 5 2 Pins description and connection diagrams 6 2.1 Pin descriptions . 6 2.2 Thermal data . 8 3 Electrical specifications 9 3.1 Absolute maximum ratings . 9 3.2 Electrical characteristic 10 4 Device description and operation . 14 5 PD interface . 16 5.1 Detection . 16 5.2 Classification 17 5.3 Under voltage lock-out . 18 5.4 In rush current limit 18 5.5 Continuos current limitation . 20 5.6 HV regulator startup . 21 5.7 Power good indication . 22 6 PWM section 23 6.1 Error amplifier and loop compensation . 23 6.2 Oscillator and sync capability 24 6.3 Soft start 25 6.4 PWM comparator / slope compensation . 26 6.5 Current limiting . 26 6.6 Leading edge blanking . 28 6.7 Thermal protection 28 2/35