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参数资料
| 型号： | ISL6844EVAL2 |
| 厂商： | Intersil |
| 文件页数： | 1/12页 |
| 文件大小： | 0K |
| 描述： | EVALUATION BOARD 2 ISL6844 |
| 标准包装： | 1 |
| 主要目的： | 特殊用途 DC/DC，以太网供电（POE） |
| 输出及类型： | 1，隔离 |
| 功率 - 输出： | 11W |
| 输出电压： | 3.3V |
| 电流 - 输出： | 3.35A |
| 输入电压： | 36 ~ 57V |
| 稳压器拓扑结构： | 回扫 |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | ISL6844 |
?
Intersil PoE Evaluation Board
Application Note
March 12, 2007
AN1192.3
Introduction
With advancements being made at a furious pace in the field
of networking, applications have started focusing on
achieving the most out of the existing infrastructure. Power
over Ethernet (PoE) is one such classic example that
integrates power and data lines. PoE consists of two power
entities: Power Sourcing Equipment (PSE) and Powered
Devices (PDs), for use with the physical layers. These utilize
the same LAN cabling (CAT-5 cables), that are used for
transmission of data, over spare twisted pair cables. Typical
applications include IP phones, WLAN access points,
security cameras and RFID tag readers, to name a few.
Scope
This document focuses on Intersil’s solution for the Powered
Device portion of the circuit, which complies with IEEE
802.3af, the standard for PoE. An inexpensive approach with
discrete circuitry has been adopted instead of an integrated
solution. With PoE soon turning into a commodity market,
low cost will be key, as compared to utilization of
sophisticated integrated solutions. The following solution has
been optimized for performance per the IEEE 802.3af
standard, with low cost and optimal performance as the
prime objectives. The evaluation board is currently available.
Powered Device (PD)
The PD needs to be able to operate with a maximum
average input power of 12.95W, and should be operational
between 36V and 57V DC. Class 0 (default) was selected for
this design, to provide the end user with maximum flexibility
with their output power requirements. Discrete classification
circuit may be added, as required, at a very low additional
cost. Other specifications selected are in line with the
requirements as specified in Table 33-12 of IEEE802.3af,
and are listed below:
Specifications Chosen for the PD Design
Operating Input Voltage range: 36V-57V DC
Max. Input Operating Current: 350mA
Max. Input Inrush Current: 400mA
Selection of the Power Topology
While selecting the topology for this application, the emphasis
was placed on two key features: optimized performance and
low cost. A simple low-power design requirement, combined
with low cost target dictated the use of a flyback converter for
this application. Given that the input power available is limited
by the PSE, high efficiency becomes an essential
requirement. The converter is being operated in the
continuous current mode to achieve this goal.
IC Selection
Intersil’s superior industry-standard ISL684x family of PWM
controllers would best serve the needs of this design. Some
key features of this family of parts include:
? Tight internal voltage reference of 1% over temperature.
? 40ns peak current sensing.
? 1A MOSFET driver
ISL6844 was selected for its large UVLO hysteresis, UVLO
start threshold, and the fact that the converter has been
designed for a maximum operational duty cycle of 50%, thus
protecting the IC by limiting the duty cycle in case of extreme
fault conditions.
Transformer Design
The design of the flyback transformer is an iterative process,
and involves the following steps:
? Calculate the energy storage needed.
? Select core geometry and material.
? Select the maximum desired flux density of operation.
? Select core size.
? Calculate the maximum flux density.
? Calculate the turns ratio.
? Select the wire gauge, number of strands, winding order
and insulation requirements.
? Estimate the losses.
? Verify the design.
Output Voltage: 3.3V
Output Current: 3.35A
Ripple: 50mV P-P
Typical Efficiency: 87%
Isolation: 1500V DC
1
While the details of the design are not discussed in this
document, as a summary, it was decided to proceed with an
EP-13 core, in order to achieve a balance of good
performance and low cost. The evaluation board provides
the end users with the option of using two other low-profile
cores for their transformer design, and can be tailored to
meet the customers’ specific requirements.
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2005-2007. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL6844EVAL3Z | 制造商:Intersil Corporation 功能描述:ISL6844 EVALUATION BOARD 3 - 8 LEAD - MSOP -ROHS COMPLIANT - Bulk 制造商:Intersil Corporation 功能描述:BOARD EVAL FOR ISL6844 |
| ISL6844IB | 功能描述:电流型 PWM 控制器 Single-End Current RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| ISL6844IB-T | 功能描述:IC REG CTRLR BST FLYBK ISO 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:100% 电源电压:8.2 V ~ 30 V 降压:无 升压:无 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:0°C ~ 70°C 封装/外壳:8-DIP（0.300"，7.62mm） 包装:管件 产品目录页面:1316 (CN2011-ZH PDF) |
| ISL6844IBZ | 功能描述:电流型 PWM 控制器 CUR MODE PWM 50% DUT Y CYCLE 14.5V UVLO RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| ISL6844IBZ-T | 功能描述:IC REG CTRLR BST FLYBK ISO 8SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
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