<div class=WordSection1> <h1>RT1985/RT1986/RT1987/RT1988 理想二极体保护开关：设计考量与应用范例</h1> <br> <p class=bady>Shihchun Liu | AN089 March 2026</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image001_zh-cn.jpg" ><img width=680 height=271 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image001_zh-cn.jpg" alt="Technical Document Image Preview"></a></p> <p class=bady>在现代电子系统中，高效的电源管理对于确保系统稳定运作与延长电池寿命至关重要。保护开关可简化不同负载的电源控制与防护，已成为关键器件之一。与分离式 MOSFET 方案相比，整合型保护开关具有体积小、保护功能强、设计简化等优势。</p> <p class=bady>立錡推出的 RT1985/RT1986/RT1987/RT1988 是高效能理想二极体保护开关，专为现代电子系统中的 USB-C/Thunderbolt 电源传输、Docking Station、Power ORing 架构所设计。本篇应用笔记将介绍产品特性、应用案例与设计重点。</p> </div> <div class=WordSection2> <br><br> <h2 id="__Bookmark__0">1 保护开关的关键功能特性 </h2> <p class=bady>RT1985/RT1986/RT1987/RT1988 具备低正向压降、可调软启动、启动短路保护及完整的异常防护功能，可有效简化电源路径管理设计并提升整体系统可靠性。相较于分离式 MOSFET 解决方案，RT1985/RT1986/RT1987/RT1988 提供更小的封装尺寸、更佳的整合性与更强的保护功能。</p> <div> <table class=TableGrid1 border=1 cellspacing=0 cellpadding=0 width=680 style='width:509.7pt;border-collapse:collapse;border:none'> <tr> <td width=90 valign=top style='width:67.15pt;border:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>Product</p> </td> <td width=126 valign=top style='width:94.85pt;border:solid windowtext 1.0pt; border-left:none;padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>Operation Vin</p> </td> <td width=161 valign=top style='width:120.8pt;border:solid windowtext 1.0pt; border-left:none;padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>Maximum Continuous Current</p> </td> <td width=146 valign=top style='width:109.35pt;border:solid windowtext 1.0pt; border-left:none;padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>OVP Threshold</p> </td> <td width=157 valign=top style='width:117.55pt;border:solid windowtext 1.0pt; border-left:none;padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpLast>Package</p> </td> </tr> <tr> <td width=90 valign=top style='width:67.15pt;border:solid windowtext 1.0pt; border-top:none;padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpFirst>RT1985</p> </td> <td width=126 valign=top style='width:94.85pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>3.4V to 23V</p> </td> <td width=161 valign=top style='width:120.8pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>8A</p> </td> <td width=146 valign=top style='width:109.35pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>Fixed</p> </td> <td width=157 valign=top style='width:117.55pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpLast>VDFN-12TL 3x3</p> </td> </tr> <tr> <td width=90 valign=top style='width:67.15pt;border:solid windowtext 1.0pt; border-top:none;padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpFirst>RT1986</p> </td> <td width=126 valign=top style='width:94.85pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>3.4V to 23V</p> </td> <td width=161 valign=top style='width:120.8pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>5.5A</p> </td> <td width=146 valign=top style='width:109.35pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>Fixed</p> </td> <td width=157 valign=top style='width:117.55pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpLast>VDFN-12TL 3x3</p> </td> </tr> <tr> <td width=90 valign=top style='width:67.15pt;border:solid windowtext 1.0pt; border-top:none;padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpFirst>RT1987</p> </td> <td width=126 valign=top style='width:94.85pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>3.4V to 32V</p> </td> <td width=161 valign=top style='width:120.8pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>8A</p> </td> <td width=146 valign=top style='width:109.35pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>Programmable</p> </td> <td width=157 valign=top style='width:117.55pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpLast>VDFN-12T1L 3x3</p> </td> </tr> <tr> <td width=90 valign=top style='width:67.15pt;border:solid windowtext 1.0pt; border-top:none;padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpFirst>RT1988</p> </td> <td width=126 valign=top style='width:94.85pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>3.4V to 53V</p> </td> <td width=161 valign=top style='width:120.8pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>8A</p> </td> <td width=146 valign=top style='width:109.35pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpMiddle>Programmable</p> </td> <td width=157 valign=top style='width:117.55pt;border-top:none;border-left: none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt; padding:0cm 5.4pt 0cm 5.4pt'> <p class=badyCxSpLast>VDFN-20TL 5.2x4</p> </td> </tr> </table> </div> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image002_zh-cn.png" ><img width=678 height=116 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image002_zh-cn.png" alt="A screenshot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=bady>图1. 保&#25252;&#24320;&#20851;的功能特性</p> <br> <h3>1.1 &#30005;源控制（开关控制）</h3> <p class=MsoNormal>保护开关不需要机械性继电器，即可简单地实现负载的电源接通与断开控制，有助于电源排序与动态功率管理。RT1985/RT1986/RT1987/RT1988 透过主动高电位（active-high）的 EN 引脚，精准控制电源通路开启时机。当 EN 为高电位且输入电压高于 UVLO 门槛时，电源通道会在给定的延迟时间后启动，并具备可控的上升电压斜率，确保上电过程稳定可。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image003_zh-cn.png" ><img width=518 height=296 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image003_zh-cn.png" alt="A screenshot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=bady><a name="_Ref197523347">图</a>2. 保&#25252;&#24320;&#20851;的啟用控制</p> <br> <h3>1.2 可程式化软启动与浪涌电流控制</h3> <p class=bady>许多保护开关透过控制闸极驱动电压来实现内建软启动功能，让输出电压与电流平滑上升。RT1985/RT1986/RT1987/RT1988 支援外部软启动电容，设计者可透过软启动电容, 设计输出电压斜率并限制浪涌电流，避免对主电源线路造成干扰，特别适用于大电容负载系统。详细设计建议请参考产品规格书。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image004_zh-cn.png" ><img width=375 height=288 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image004_zh-cn.png" alt="A diagram of a device&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=bady><a name="_Ref197523649">图</a>3. 不具备浪涌电流控制的启动</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image005_zh-cn.png" ><img width=371 height=293 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image005_zh-cn.png" alt="Technical Document Image Preview"></a></p> <p class=MsoNormal><a name="_Ref197523661">图</a>4. 具备浪涌&#30005;流控制的&#21551;&#21160;</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image006_zh-cn.png" ><img width=672 height=366 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image006_zh-cn.png" alt="A screen shot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>图5. RT1985 的&#36719;&#21551;&#21160;&#27979;&#35797;結果</p> <br> <h3>1.3 启动短路保护 (SCP)</h3> <p class=bady>在启动过程中，RT1985/RT1986/RT1987/RT1988 会持续监控输出电流。若侦测到异常的浪涌电流或硬短路（Hard Short），装置将主动关闭输出并在给定的延迟时间后自动重启（Auto Retry），即使在故障条件下也能提供安全保护。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image007_zh-cn.png" ><img width=402 height=156 id="Picture 19" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image007_zh-cn.png" alt="A black background with red and blue text&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal><a name="_Ref197523668">图</a>6. 以 MOSFET 作为保护开关的应用</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image008_zh-cn.png" ><img width=444 height=174 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image008_zh-cn.png" alt="A screenshot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>图7. 使用 RT1985/RT1986/RT1987/RT1988 作为保&#25252;&#24320;&#20851;的应用</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image009_zh-cn.png" ><img width=673 height=371 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image009_zh-cn.png" alt="A screen shot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>图8. RT1985 启动时遇短路与重新启动的测试结果</p> <br> <h3>1.4 反向电流阻断</h3> <p class=bady>在多电源备援或 ORing 系统中，防止电流回流至输入端是很重要的条件。RT1985/RT1986/RT1987/RT1988 具备 Ideal Diode 真实反向电流阻断（TRCB）功能，能稳定控制正向压降并有效防止电流自 VOUT 回灌至 VIN，是实现多源供电应用的关键技术。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image010_zh-cn.png" ><img width=535 height=248 id="Picture 20" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image010_zh-cn.png" alt="A diagram of electrical wiring&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>图9. 从输出端回灌至输入端的反向电流阻断</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image011_zh-cn.png" ><img width=655 height=365 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image011_zh-cn.png" alt="A screen shot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal><a>图</a>10. RT1985 反向电流阻断保护测试结果</p> <br> <h3>1.5 过电压保护 (OVP)</h3> <p class=bady>RT1985/RT1986/RT1987/RT1988 整合输入过电压保护功能，当输入电压超过阈值时，会自动切断电源通路，避免下游电路受损。此功能特别适用于 USB-C 与多源供电架构，能有效因应来自不稳定输入源的电压冲击。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image012_zh-cn.png" ><img width=537 height=223 id="Picture 11" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image012_zh-cn.png" alt="A black screen with red and green text&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>图11. 输入电压过高时的过电压保护机制</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image013_zh-cn.png" ><img width=658 height=349 id="Picture 15" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image013_zh-cn.png" alt="Technical Document Image Preview"></a></p> <p class=MsoNormal>图12. RT1985 过电压保护测试结果</p> <br> <h3>1.6 过温关机保护</h3> <p class=bady>高阶保护开关通常内建温度监控机制。当晶片温度超过安全阈值（约 140°C）时，RT1985/RT1986/RT1987/RT1988 会自动关闭输出，并启动错误提示，以防止永久性损坏，进一步提升系统可靠性。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image014_zh-cn.png" ><img width=579 height=214 id="Picture 12" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image014_zh-cn.png" alt="A screen shot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>图13. 异常高温状况下的过温保护机制</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image015_zh-cn.png" ><img width=621 height=336 id="Picture 38" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image015_zh-cn.png" alt="A screen shot of a graph&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal><a>图</a>14. RT1985 过温保护&#27979;&#35797;結果 </p> <br> <h3>1.7 低导通电阻 (20mΩ)</h3> <p class=bady>RT1985/RT1986/RT1987/RT1988 采用先进工艺设计，将内部 MOSFET 导通电阻 (RON) 压低至 20mΩ，降低在传输高电流时所产生的功率损耗 (P = I²R)。这不仅减少器件发热，还能提高整体散热效率。</p> <br> <h3>1.8 极低静态电流</h3> <p class=bady>RT1985/RT1986/RT1987/RT1988 具备极低的静态电流设计，意味着在无负载或轻负载条件下，IC 本身的耗电量极低，进一步优化整机功耗表现，延长电池使用，适合应用于便携式装置（如笔电、平板）。</p> <br><br> <h2 id="__Bookmark__1">2 应用范例</h2> <h3>2.1 USB-C / Thunderbolt Sink &#30005;源应用</h3> <p class=bady>保护开关在 USB-C 与 Thunderbolt 应用中扮演关键角色，不仅提供电源控制功能，也可保护系统在动态功率协商过程中避免浪涌与反灌风险。RT1985 可同时管理 Sink 与 Source 电源路径，应用于双埠 USB PD 装置中。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image016_zh-cn.png" ><img width=697 height=426 id="Picture 10" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_cn/image016_zh-cn.png" alt="Technical Document Image Preview"></a></p> <p class=MsoNormal><a name="_Ref197523675">图</a>15. RT1985 应用于双埠 USB PD 系统中的 Sink 与 Source 控制</p> <p class=MsoNormal>注：上述系统图仅供参考，实际应用需依照产品规格调整。若需协助，请联系立錡业务窗口。</p> <br> <h3>2.2 &#25193;展底座 Docking Station</h3> <p class=bady>在笔电与平板扩展底座设计中，保护开关可用于选择性启用各项 I/O 埠或周边设备，提升系统功耗效率、降低待机损耗、实现故障隔离。</p> <br> <h3>2.3 多&#30005;源 ORing 应用</h3> <p class=bady>具备真实反向电流阻断能力的保护开关，能实现可靠的多电源 ORing 应用。无论是交流转接器、电池或备援供电，皆可实现顺畅切换，确保电源不中断并提升系统稳定性。</p> <br><br> <h2 id="__Bookmark__2">3 结论</h2> <p class=bady>适当地整合保护开关可提升系统可靠性、简化电源设计，并优化整体效能。在电源架构日益复杂的今天，保护开关已成为智慧电源管理中不可或缺的一环。RT1985/RT1986/RT1987/RT1988 结合理想二极体反向阻断、可调软启动、完整保护功能与小型封装设计，是 USB-C、Docking Station 与 Power ORing 等高需求应用的理想选择，协助设计者简化开发流程、提升产品可靠度与使用者体验。</p> </div> <br><br><br> <table border="1" cellspacing="0" cellpadding="0" style="width: 637.5pt; border-collapse: collapse; border: medium none;" class="3-51"> <tbody> <tr style="height: 17pt;"> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: #009eb8; background-color: #009eb8; background-image: url(e); background-repeat: repeat; background-attachment: scroll; background-clip: border-box; background-origin: padding-box; background-size: auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;" colspan="2"> <span style="color: #ffffff;">相关资源</span> </td> </tr> <tr> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: #009eb8; background-color: #ffffff; background-image: url(e); background-repeat: repeat; background-attachment: scroll; background-clip: border-box; background-origin: padding-box; background-size: auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> 立錡科技电子报 </td> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: #009eb8; background-color: #ffffff; background-image: url(e); background-repeat: repeat; background-attachment: scroll; background-clip: border-box; background-origin: padding-box; background-size: auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> <a class="link" href="http://www.richtek.com/My%20Richtek/Newsletters" target="_blank">订阅立錡科技电子报</a> </td> </tr> <tr> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: #009eb8; background-color: #ffffff; background-image: url(e); background-repeat: repeat; background-attachment: scroll; background-clip: border-box; background-origin: padding-box; background-size: auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> 档案下载 </td> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: #009eb8; background-color: #ffffff; background-image: url(e); background-repeat: repeat; background-attachment: scroll; background-clip: border-box; background-origin: padding-box; background-size: auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> <a class="link" href=" ~/media/1813D6E14E6E49C78002C04AB8AD3B3C.ashx">PDF 下载</a> </td> </tr> </tbody> </table>

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