原标题：TI TIDA－010034 IP网络照相机IEEE802.3attype－1PoE参考设计

　　TI公司的TIDA-010034是用于IP网络照相机的IEEE802.3at type-1 PoE和12V点负载(POL)的参考设计.该参考设计是基于TI公司的DaVinci™数字媒体处理器或不同应用处理器的采用PoE或12V适配器端到端的IP网络照相机供电树.该供电树也能驱动IP网络照相机的不同外设如图像传感器,马达控制,以太网PHY,RS-485接口,IR LED照明,音频,运动检测和告警接口.参考设计TIDA-010034具有无光耦反激DC/DC控制器的TPS23755 IEEE802.3at PoE PD,用于type-1 PoE的完整的IEEE802.3at PD解决方案,集成了带初级边调整(PSR)的反激控制器,频率抖动和高级启动,PoE供电反激功率级12V输出的效率为89%,具有平滑转换的次级侧适配器优先级控制,具有两种功率树:1)高频,12V到PoL,采用中等输入范围的降压转换器,2)低成本,12V到5V到PoL,材用低输入范围降压转换器.两种功率树具有FPWM模式,具有用于处理动态负载切换的快速瞬态响应和电压轨上的低输出电压波纹如MPU核和DDR RAM所要求的那样.本文介绍了参考设计TIDA-010034主要特性和主要系统指标,框图和测试建立图,电路图,材料清单和PCB设计图.

　　Power over Ethernet (PoE) enables power to bedelivered over the same ethernet cable as data with nodanger of cross-talk, interference, or corruption of thedata streams. This reference design showcases endto-end power tree for an IP network camera poweredusing PoE or 12-V adapter based on TI’s DaVinci™Digital Media Processor or different applicationprocessor. The power tree also derives rails requiredfor different peripherals of an IP network camera like:Image sensor, motor control, Ethernet PHY, RS485interface, IR LED illumination, audio, motion sensingand the alarm interface.

　　An IP based Ethernet network infrastructure is often already in place, which means the IP camera caneasily be connected to the nearest network connection. Simply setup the IP address and you’re up andrunning! Adding more IP cameras to a system is as easy as the first one. The ability to provide electricalpower to an IP camera is an important aspect of IP video surveillance that is not available in analogsecurity camera deployments. Analog cameras require some external power supply to meet the powerrequirements of the cameras. With the facility of Power over Ethernet (PoE) - supplying power directlyover the network cable - an external power supply is optional, making installation much easier. DeployingIP cameras, whether indoor or outdoor, requires Power over Ethernet (PoE). Power over Ethernettechnology saves time and cost of installing separate power cabling, AC outlets and wall warts, as well aseliminates the need for a dedicated UPS for individual devices. Most IP cameras in the market come withdual or triple power supply options for greater flexibility in terms of utilizing existing AC or DC powerinfrastructure in the buildings. The multiple power supply input options (PoE + DC input, PoE + AC input　orPoE + DC + AC) also provides redundant power supply protection ensuring 24/7 reliability.

　　The IEEE802.3at type-1 PoE and 12-V adapter input to point-of-load reference design for IP networkcamera is a high efficiency, low cost and small form-factor complete power tree for an IP network camera.

　　This reference design presents two most popular power tree implementations – first, PoE + 12V to POLsdirectly using mid-VIN range synchronous buck converters optimized for highest efficiency and second,PoE + 12V to 5V and then to POLs using one mid-VIN range buck converter followed by several low-VINrange buck converters optimized for low cost and reasonably high efficiency. This reference design takescare of complete power supply of an IP network camera based on the TI’s DaVinci™ Digital Media　Processor and different peripheral functions. This reference design system can also be adopted withminimal modifications for IP network cameras based on similar application processors. The power modulealso consists of rails required for different peripherals of an IP network camera like: Image sensor, motorcontrol, Ethernet PHY, RS485 interface, IR LED illumination, audio, motion sensing and the alarminterface.

　　At a high level, this reference design consists of a Power-over-Ethernet (PoE) Powered Device (PD) withintegrated DC/DC, Synchronous Buck Converters with Switch and low noise, high PSRR LDOs togenerated different voltage rails required for an IP network camera. The Power-over-Ethernet (PoE)Powered Device (PD) is IEEE 802.3at Type-1 PD supporting up to 13-W with integrated current-mode DCDCcontroller optimized for flyback topology. The synchronous step-down buck converters with forcedPWM feature in SOT-563 package have been optimized for reduces output voltage ripple, fast transient　response, high efficiency and compact solution size. This reference design provides a complete set ofdownloadable documents such as a comprehensive design guide, schematic, Altium PCB layout files, billof materials (BOM), test results, and Gerber files that help system designers in the design anddevelopment of their end-equipment systems. The following subsections describe the various blocks withinthe reference design system and what characteristics are most critical to best implement the corresponding function.

　　参考设计TIDA-010034主要特性:

　　• TPS23755 IEEE802.3at PoE PD with no-optoflyback DC-DC controller

　　– Complete IEEE802.3at PD solution for type-1PoE

　　– Integrated flyback controller with primary sideregulation (PSR), frequency dithering and advanced startup

　　– 12-V output, 89% efficiency of the PoE-poweredflyback power stage

　　– Secondary side adapter priority control withsmooth transition

　　• No diode ORing: 88% less power dissipation inadapter input path with TPS2121 power MUX forsecondary side ORing

　　• Two power tree implementations:

　　– For high efficiency: 12-V to PoL, using mid inputrange buck converters

　　– For low cost: 12-V to 5-V to PoL, using lowinput range buck converters

　　• Both power trees use buck converters with FPWMmode enabling:

　　– Fast transient response for handling dynamicload switching on rails suppling power to MPUcore and DDR RAM

　　– Low output voltage ripple on voltage rails withtighter tolerances like MPU core and DDR RAM

　　参考设计TIDA-010034应用:

　　• IP network camera

　　•Daylight sensor

　　参考设计TIDA-010034主要系统指标:

　　图1.参考设计TIDA-010034框图

　　图2.参考设计TIDA-010034测试建立图

　　图3.参考设计TIDA-010034外形图

　　参考设计TIDA-010034材料清单: