<div class=WordSection1> <h1>RT1985/RT1986/RT1987/RT1988 理想二極體保護開關：設計考量與應用範例</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_tw/image001_zh-tw.jpg" ><img width=680 height=271 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image001_zh-tw.jpg" alt="Technical Document Image Preview"></a></p> <p class=bady>在現代電子系統中，高效的電源管理對於確保系統穩定運作與延長電池壽命至關重要。保護開關可簡化不同負載的電源控制與防護，已成為關鍵元件之一。與分離式 MOSFET 方案相比，整合型保護開關具有體積小、保護功能強、設計簡化等優勢。</p> <p class=bady>立錡推出的 <a name="_Hlk199348285">RT1985/</a><a name="_Hlk199346841">RT1986</a>/RT1987/RT1988 是高效能理想二極體保護開關，專為現代電子系統中的 USB-C / Thunderbolt 電源傳輸、Docking Station、Power ORing 架構所設計。本篇應用筆記將介紹產品特性、應用案例與設計重點。</p> </div> <div class=WordSection2> <br><br> <h2 id="__Bookmark__0">1 保護開關的關鍵功能特性 </h2> <p class=bady>RT1985/RT1986/RT1987/RT1988 具備低正向壓降、可調軟啟動、啟動短路保護及完整的異常防護功能，可有效簡化電源路徑管理設計並提升整體系統可靠性。相較於分離式 MOSFET 解決方案，RT1985/RT1986/RT1987/RT1988 提供更小的封裝尺寸、更佳的整合性與更強的保護功能。</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_tw/image002_zh-tw.png" ><img width=678 height=116 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image002_zh-tw.png" alt="A screenshot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=bady>圖1. 保護開關的功能特性</p> <br> <h3>1.1 電源控制（開關控制）</h3> <p class=MsoNormal>保護開關不需要機械性繼電器，即可簡單地實現負載的電源接通與斷開控制，有助於電源排序與動態功率管理。RT1985/RT1986/RT1987/RT1988 透過主動高電位（active-high）的 EN 腳位，精準控制電源通路開啟時機。當 EN 為高電位且輸入電壓高於 UVLO 門檻時，電源通道會在給定的延遲時間後啟動，並具備可控的上升電壓斜率，確保上電過程穩定可靠。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image003_zh-tw.png" ><img width=518 height=296 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image003_zh-tw.png" alt="A screenshot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=bady><a name="_Ref197523347">圖</a>2. 保護開關的啟用控制</p> <br> <h3>1.2 可調式軟啟動與浪湧電流控制</h3> <p class=bady>許多保護開關透過控制閘極驅動電壓來實現內建軟啟動功能，讓輸出電壓與電流平滑上升。RT1985/RT1986/RT1987/RT1988 支援外部軟啟動電容，設計者可透過軟啟動電容, 設計輸出電壓斜率並限制浪湧電流，避免對主電源線路造成干擾，特別適用於大電容負載系統。詳細設計建議請參考產品規格書。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image004_zh-tw.png" ><img width=375 height=288 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image004_zh-tw.png" alt="A diagram of a device&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=bady><a name="_Ref197523649">圖</a>3. 不具備浪湧電流控制的啟動</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image005_zh-tw.png" ><img width=371 height=293 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image005_zh-tw.png" alt="A screenshot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal><a name="_Ref197523661">圖</a>4. 具備浪湧電流控制的啟動</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image006_zh-tw.png" ><img width=672 height=366 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image006_zh-tw.png" alt="A screen shot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>圖5. RT1985 的軟啟動測試結果</p> <br> <h3>1.3 啟動短路保護 (SCP)</h3> <p class=bady>在啟動過程中，RT1985/RT1986/RT1987/RT1988 會持續監控輸出電流。若偵測到異常的浪湧電流或硬短路（Hard Short），裝置將主動關閉輸出並在給定的延遲時間後自動重啟（Auto Retry），即使在故障條件下也能提供安全保護。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image007_zh-tw.png" ><img width=402 height=156 id="Picture 19" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image007_zh-tw.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">圖</a>6. 以 MOSFET 作為保護開關的應用</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image008_zh-tw.png" ><img width=444 height=174 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image008_zh-tw.png" alt="A screenshot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>圖7. 使用 RT1985/RT1986/RT1987/RT1988 作為保護開關的應用</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image009_zh-tw.png" ><img width=673 height=371 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image009_zh-tw.png" alt="A screen shot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>圖8. RT1985 啟動時遇短路與重新啟動的測試結果</p> <br> <h3>1.4 反向電流阻斷</h3> <p class=bady>在多電源備援或 ORing 系統中，防止電流回流至輸入端是很重要的條件。RT1985/RT1986/RT1987/RT1988 具備 Ideal Diode 真實反向電流阻斷（TRCB）功能，能穩定控制正向壓降並有效防止電流自 VOUT 回灌至 VIN，是實現多源供電應用的關鍵技術。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image010_zh-tw.png" ><img width=535 height=248 id="Picture 20" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image010_zh-tw.png" alt="A diagram of electrical wiring&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>圖9. 從輸出端回灌至輸入端的反向電流阻斷</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image011_zh-tw.png" ><img width=655 height=365 src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image011_zh-tw.png" alt="A screen shot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal><a>圖</a>10. RT1985 反向電流阻斷保護測試結果</p> <br> <h3>1.5 過電壓保護 (OVP)</h3> <p class=bady>RT1985/RT1986/RT1987/RT1988 整合輸入過電壓保護功能，當輸入電壓超過閾值時，會自動切斷電源通路，避免下游電路受損。此功能特別適用於 USB-C 與多源供電架構，能有效因應來自不穩定輸入源的電壓衝擊。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image012_zh-tw.png" ><img width=537 height=231 id="Picture 11" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image012_zh-tw.png" alt="A black screen with red and green text&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>圖11. 輸入電壓過高時的過電壓保護機制</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image013_zh-tw.png" ><img width=658 height=349 id="Picture 15" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image013_zh-tw.png" alt="Technical Document Image Preview"></a></p> <p class=MsoNormal>圖12. RT1985 過電壓保護測試結果</p> <br> <h3>1.6 過溫關機保護</h3> <p class=bady>高階保護開關通常內建溫度監控機制。當晶片溫度超過安全閾值（約 140°C）時，RT1985/RT1986/RT1987/RT1988 會自動關閉輸出，並啟動錯誤提示，以防止永久性損壞，進一步提升系統可靠性。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image014_zh-tw.png" ><img width=579 height=217 id="Picture 12" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image014_zh-tw.png" alt="A screen shot of a computer&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal>圖13. <a>異常高溫狀況下的過溫保護機制</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image015_zh-tw.png" ><img width=621 height=336 id="Picture 38" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image015_zh-tw.png" alt="A screen shot of a graph&#10;&#10;AI-generated content may be incorrect."></a></p> <p class=MsoNormal><a>圖</a>14. RT1985 過溫保護測試結果</p> <br> <h3>1.7 低導通電阻 (20mΩ)</h3> <p class=bady>RT1985/RT1986/RT1987/RT1988 採用先進工藝設計，將內部MOSFET導通電阻（R_ON）壓低至20mΩ，有效降低在傳輸高電流時所產生的功率損耗（P = I&sup2;R）。這不僅減少元件發熱，還能提高整體散熱效率。</p> <br> <h3>1.8 極低靜態電流</h3> <p class=bady>RT1985/RT1986/RT1987/RT1988 具備極低的靜態電流設計，意味著在無負載或輕負載條件下，IC 本身的耗電量極低，進一步優化整機功耗表現，延長電池使用，適合應用於便攜式裝置（如筆電、平板）。</p> <br><br> <h2 id="__Bookmark__1">2 應用範例</h2> <h3>2.1 USB-C / Thunderbolt Sink 電源應用</h3> <p class=bady>保護開關在 USB-C 與 Thunderbolt 應用中扮演關鍵角色，不僅提供電源控制功能，也可保護系統在動態功率協商過程中避免浪湧與反灌風險。RT1985 可同時管理 Sink 與 Source 電源路徑，應用於雙埠 USB PD 裝置中。</p> <p class=bady><a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image016_zh-tw.png" ><img width=697 height=426 id="Picture 10" src="/content/dam/richtek-eds/resources/application-notes/an089/html-images-zh_tw/image016_zh-tw.png" alt="Technical Document Image Preview"></a></p> <p class=MsoNormal><a name="_Ref197523675">圖</a>15. RT1985 應用於雙埠 USB PD 系統中的 Sink 與 Source 控制</p> <p class=MsoNormal>註：上述系統圖僅供參考，實際應用需依照產品規格調整。若需協助，請聯繫立錡業務窗口。</p> <br> <h3>2.2 擴充底座Docking Station</h3> <p class=bady>在筆電與平板擴充底座設計中，保護開關可用於選擇性啟用各項 I/O 埠或週邊設備，提升系統功耗效率、降低待機損耗、實現故障隔離。</p> <br> <h3>2.3 多電源 ORing 應用</h3> <p class=bady>具備真實反向電流阻斷能力的保護開關，能實現可靠的多電源 ORing 應用。無論是交流轉接器、電池或備援供電，皆可實現順暢切換，確保電源不中斷並提升系統穩定性。</p> <br><br> <h2 id="__Bookmark__2">3 結論</h2> <p class=bady>適當地整合保護開關可提升系統可靠性、簡化電源設計，並優化整體<a>效能。在電源架構日益複雜的今天，保護開關已成為智慧電源管理中不可或缺的一環。RT1985/RT1986/RT1987/RT1988 結合理想二極體反向阻斷、可調軟啟動、完整保護功能與小型封裝設計，是 USB-C、Docking Station 與 Power ORing 等高需求應用的理想選擇，協助設計者簡化開發流程、提升產品可靠度與使用者體驗。</p> </div> <div> </div> <br><br><br> <table class="3-51" style="border: currentColor; border-image: none; width: 637.5pt; border-collapse: collapse;" border="1" cellspacing="0" cellpadding="0"> <tbody> <tr> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: rgb(0, 158, 184); height: 17pt; padding-right: 5pt; padding-left: 5pt; background-image: url(e); background-attachment: scroll; background-repeat: repeat; background-size: auto auto; background-origin: padding-box; background-clip: border-box; background-color: rgb(0, 158, 184);" colspan="2"> <span style="color: rgb(255, 255, 255);">相關資源</span> </td> </tr> <tr> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: rgb(0, 158, 184); height: 17pt; padding-right: 5pt; padding-left: 5pt; background-image: url(e); background-attachment: scroll; background-repeat: repeat; background-size: auto auto; background-origin: padding-box; background-clip: border-box; background-color: rgb(255, 255, 255);"> 立錡科技電子報 </td> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: rgb(0, 158, 184); height: 17pt; padding-right: 5pt; padding-left: 5pt; background-image: url(e); background-attachment: scroll; background-repeat: repeat; background-size: auto auto; background-origin: padding-box; background-clip: border-box; background-color: rgb(255, 255, 255);"> <a class="link" href="http://www.richtek.com/My%20Richtek/Newsletters" target="_blank"> 訂閱立錡科技電子報</a> </td> </tr> <tr style="height: 17pt;"> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: rgb(0, 158, 184); height: 17pt; padding-right: 5pt; padding-left: 5pt; background-image: url(e); background-attachment: scroll; background-repeat: repeat; background-size: auto auto; background-origin: padding-box; background-clip: border-box; background-color: rgb(255, 255, 255);"> 檔案下載 </td> <td style="border-width: 1pt 1px 1px 1pt; border-style: solid; border-color: rgb(0, 158, 184); height: 17pt; padding-right: 5pt; padding-left: 5pt; background-image: url(e); background-attachment: scroll; background-repeat: repeat; background-size: auto auto; background-origin: padding-box; background-clip: border-box; background-color: rgb(255, 255, 255);"> <a class="link" href="~/media/FA3857442E02424D88A6367CF49855EB.ashx"> PDF 下載</a> </td> </tr> </tbody> </table>

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