AS1138

Akros Silicon, Inc.

6399 San Ignacio Avenue, Suite 250, San Jose, CA 95119 USA

408.746.9000

www.AkrosSilicon.com

2

TABLE OF CONTENTS

GENERAL DESCRIPTION ..............................................................................................................................................................1

TYPICAL APPLICATIONS...............................................................................................................................................................1

SIMPLIFIED APPLICATION DIAGRAM ..........................................................................................................................................1

FEATURES .....................................................................................................................................................................................1

FIGURES.........................................................................................................................................................................................3

TABLES...........................................................................................................................................................................................3

PIN DIAGRAM .................................................................................................................................................................................4

PACKAGE THERMAL CHARACTERISTICS ..................................................................................................................................7

TYPICAL PERFORMANCE CHARACTERISTICS ..........................................................................................................................8

FUNCTIONAL DESCRIPTION ......................................................................................................................................................15

OVERVIEW OF POE.....................................................................................................................................................................15

AS1138 POE DESIGN...................................................................................................................................................................15

POWER FEED ALTERNATIVES FOR 10/100/1000 ETHERNET SYSTEMS ...............................................................................16

AS1138 OVERVIEW......................................................................................................................................................................17

RECTIFICATION AND PROTECTION ..........................................................................................................................................18

PD CONTROLLER ........................................................................................................................................................................18

MODES OF OPERATION .............................................................................................................................................................18

RESET...........................................................................................................................................................................................18

DETECTION MODE ......................................................................................................................................................................18

CLASSIFICATION MODE .............................................................................................................................................................18

IDLE MODE ...................................................................................................................................................................................19

ON STATE.....................................................................................................................................................................................19

LOCAL POWER MODE (LVMODE) ..............................................................................................................................................19

PD CONTROLLER POWER AND THERMAL PROTECTION.......................................................................................................21

UNDER VOLTAGE LOCK OUT (UVLO)........................................................................................................................................21

INRUSH CURRENT LIMIT / CURRENT SENSE...........................................................................................................................21

THERMAL LIMIT / PROTECTION .................................................................................................................................................21

POE POWER-ON STARTUP WAVEFORM ..................................................................................................................................22

ATDET PIN ....................................................................................................................................................................................23

DC-DC CONTROLLER..................................................................................................................................................................24

OVERVIEW ...................................................................................................................................................................................24

PROGRAMMABLE PWM FREQUENCY.......................................................................................................................................24

CURRENT-LIMIT/CURRENT SENSE ...........................................................................................................................................24

LOW LOAD CURRENT OPERATION ...........................................................................................................................................24

COMPENSATION AND FEEDBACK.............................................................................................................................................24

SOFT-START ................................................................................................................................................................................24

DC-DC CONVERTER TOPOLOGIES ...........................................................................................................................................25

ISOLATED TOPOLOGIES ............................................................................................................................................................25

NON-ISOLATED TOPOLOGIES ...................................................................................................................................................25

APPLICATION CIRCUITS .............................................................................................................................................................26

THERMAL DE-RATING AND BOARD LAYOUT CONSIDERATIONS ..........................................................................................27

PHYSICAL DIMENSIONS .............................................................................................................................................................28

CONTACT INFORMATION ...........................................................................................................................................................29

IMPORTANT NOTICES.................................................................................................................................................................29

LEGAL NOTICE.............................................................................................................................................................................29

REFERENCE DESIGN POLICY....................................................................................................................................................29

LIFE SUPPORT POLICY...............................................................................................................................................................29

SUBSTANCE COMPLIANCE ........................................................................................................................................................30