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<div class="WordSection1"> <h1>DCR温度补偿</h1> <p><br></p> <h2 id="__Bookmark__0">摘要</h2> <p>DCR电流检测技术,因其具有无损耗之优点,是一个能获得正确电感电流讯息的好方法。然而,金属铜本身具有正温度系数,所以电感的 DCR 值会随温度变化而改变。而随温度变化的DCR 值,就会使控制器检测到不正确的电流信号。 常用的解决方式是在电流检测回路中加上 DCR 温度网络,以避免此温度效应。故此,本应用须知将介绍 DCR 温度补偿的基本概念和电路实现的方法。</p> <p class="MsoNormal"><br><br></p> <h2 id="__Bookmark__1">1.为何需要DCR温度补偿网络</h2> <p>图一所示为一 DCR 电流检测网络。当时间常数相等,也就是 C<sub>x</sub>R<sub>x</sub> = L / DCR 时,如式(1)所示,V<sub>CX</sub>电压可用来取得电感电流信号。然而, DCR 值会以正比随温度增加,如式(2)所示,其中参数 TC<sub>DCR</sub> 是铜的温度系数,且是一正数。当电路在重载条件下工作时,电感的温度也会随之增加。这使得稳压器会因随温度改变的 DCR 值,检测到错误的负载电流值,进而回报不正确的电流讯息。此外,也会使得输出电压无法达到其该有的值,也因此就无法满足在 V<sub>CORE</sub> 应用中所需要的适应性电压定位 (AVP) 下垂的负载线规格。所以,在此探讨的温度补偿网络就是为了解决这个问题。</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image001_zh-cn.jpg"> <img id="圖片 1" alt="Technical Document Image Preview" height="46" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image001_zh-cn.jpg" width="321"></a></p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image002_zh-cn.jpg"> <img id="圖片 3" alt="Technical Document Image Preview" height="138" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image002_zh-cn.jpg" width="234"></a></p> <p class="MsoNormal">图一、DCR电流检测网络</p> <p class="MsoNormal"><br><br></p> <h2 id="__Bookmark__2">2. DCR 温度补偿之架构</h2> <p>DCR温度补偿网络的目的就是使 DCR 值不随温度改变,因此使得 V<sub>CX</sub> 电压只和电感电流有关。因为 DCR 是一具有正温度系数的电阻,所以就必须在电流检测回路中插入一个有负温度系数的电阻性网络,以补偿 DCR 随温度的变化。当有 Y个温度点需要进行补偿,补偿网络就需要 Y 个电阻和一个负温度系数(NTC)的热敏电阻,如此才能在这 Y 个温度点时,DCR 值的温度变化均可被抵消。然而,不同的电流检测架构,DCR温度补偿网络的设计方式也不同。图二和图三分别显示了总和电流检测架构 (sum current sensing topology) 和差分电流检测架构 (differential current sensing topology) 的温度补偿网络,及其电路示意图。总和电流检测架构示范的是有三个温度点作补偿的补偿网络,而差分电流检测架构则示范的是有两个温度点作补偿的补偿网络。式(3)和式(4)可分别作为这两个电流检测架构的设计原则。</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image003_zh-cn.jpg"> <img id="圖片 8" alt="Technical Document Image Preview" height="87" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image003_zh-cn.jpg" width="344"></a></p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image004_zh-cn.jpg"> <img id="圖片 9" alt="Technical Document Image Preview" height="470" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image004_zh-cn.jpg" width="658"></a></p> <p class="MsoNormal">图二、总和电流检测架构之DCR温度补偿网络</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image005_zh-cn.jpg"> <img id="圖片 10" alt="Technical Document Image Preview" height="547" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image005_zh-cn.jpg" width="672"></a></p> <p class="MsoNormal">图三、差分电流检测架构之DCR温度补偿网络</p> <p class="MsoNormal"><br><br></p> <h2 id="__Bookmark__3">3. DCR 温度补偿网络之公式推导</h2> <p>在本节中,将以总和电流检测架构为例,说明如何推导出温度补偿网络。如式(3),藉由 V<sub>sum</sub> 电压及一个适当的比例,即可得到正确负载电流的讯息;此比例为R<sub>sum</sub> 和(R<sub>x</sub>+R<sub>s</sub>)之比,如式 (5)所示。以 RT8893 例,此值必须设为4,才能有正常的操作。</p> <p> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image006_zh-cn.jpg"> <img id="圖片 12" alt="Technical Document Image Preview" height="41" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image006_zh-cn.jpg" width="233"></a></p> <p>而为了消除温度对 DCR 的影响,必须在 R<sub>sum</sub> 网络中插入一个 NTC 热敏电阻,使得 V<sub>sum</sub> 电压不会随温度改变。 NTC热敏电阻和温度之间的关系如式(6),其中 β 是 NTC 的温度系数;不同的 NTC 热敏电阻,β 值也会不同。</p> <p> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image007_zh-cn.jpg"> <img id="圖片 13" alt="Technical Document Image Preview" height="37" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image007_zh-cn.jpg" width="286"></a></p> <p>如果是有三个温度点(TL、TR和TH)需要进行补偿,则在此三个温度点,V<sub>sum</sub> 电压必须相同;也就是如式(7)之右侧所示之结果,与温度无关。R<sub>sum</sub>(T) 为内含 NTC 热敏电阻的热补偿网络之等效电阻,其表示式为式(8)。</p> <p> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image008_zh-cn.jpg"> <img id="圖片 14" alt="Technical Document Image Preview" height="96" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image008_zh-cn.jpg" width="348"></a></p> <p>因此,由以上公式,R<sub>sum</sub> 网络之各参数可分别由公式(9),(10),和(11)得出。详细之推导,可参阅附录 I。</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image009_zh-cn.jpg"> <img id="圖片 15" alt="Technical Document Image Preview" height="123" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image009_zh-cn.jpg" width="348"></a></p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image010_zh-cn.jpg"> <img id="圖片 16" alt="Technical Document Image Preview" height="77" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image010_zh-cn.jpg" width="566"></a></p> <p>在经过温度补偿电路之后,V<sub>SUM</sub> 在这三个温度点的误差(例如:20°C, 60°C, 和 100°C)应当为零,如图四所示。</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image011_zh-cn.jpg"> <img id="圖片 11" alt="Technical Document Image Preview" height="455" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image011_zh-cn.jpg" width="680"></a></p> <p class="MsoNormal">图四、DCR温度补偿后之V<sub>SUM</sub>误差 </p> <p class="MsoNormal"><br><br></p> <h2 id="__Bookmark__4">4. DCR 温度补偿网络的设计范例</h2> <p>以下设计方法所选用的是总和电流检测架构,并以 RT8893 作为设计范例;所订的规格是根据英特尔VR12.5的设计需求。</p> <div> <table border="1" cellpadding="0" cellspacing="0" class="MsoTableLightListAccent5" style="width: 40.24%; border-collapse: collapse; border: none" width="40%"> <tr> <td colspan="2" style="width: 100.0%; border: solid #4BACC6 1.0pt; border-bottom: none; background: #4BACC6; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="100%"> <p class="MsoNormal">VCORE 规格</p> </td> </tr> <tr> <td style="width: 62.16%; border: solid #4BACC6 1.0pt; border-right: solid #009EB8 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="62%"> <p class="MsoNormal">输入电压</p> </td> <td style="width: 37.84%; border: solid #4BACC6 1.0pt; border-left: none; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="37%"> <p class="MsoNormal">10.8V to 13.2V</p> </td> </tr> <tr> <td style="width: 62.16%; border-top: none; border-left: solid #4BACC6 1.0pt; border-bottom: none; border-right: solid #009EB8 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="62%"> <p class="MsoNormal">相位数</p> </td> <td style="width: 37.84%; border: none; border-right: solid #4BACC6 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="37%"> <p class="MsoNormal">3</p> </td> </tr> <tr> <td style="width: 62.16%; border: solid #4BACC6 1.0pt; border-right: solid #009EB8 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="62%"> <p class="MsoNormal">Vboot</p> </td> <td style="width: 37.84%; border: solid #4BACC6 1.0pt; border-left: none; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="37%"> <p class="MsoNormal">1.7V</p> </td> </tr> <tr> <td style="width: 62.16%; border-top: none; border-left: solid #4BACC6 1.0pt; border-bottom: none; border-right: solid #009EB8 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="62%"> <p class="MsoNormal">VDAC(MAX)</p> </td> <td style="width: 37.84%; border: none; border-right: solid #4BACC6 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="37%"> <p class="MsoNormal">1.8V</p> </td> </tr> <tr> <td style="width: 62.16%; border: solid #4BACC6 1.0pt; border-right: solid #009EB8 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="62%"> <p class="MsoNormal">ICCMAX</p> </td> <td style="width: 37.84%; border: solid #4BACC6 1.0pt; border-left: none; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="37%"> <p class="MsoNormal">90A</p> </td> </tr> <tr> <td style="width: 62.16%; border-top: none; border-left: solid #4BACC6 1.0pt; border-bottom: none; border-right: solid #009EB8 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="62%"> <p class="MsoNormal">ICC-DY</p> </td> <td style="width: 37.84%; border: none; border-right: solid #4BACC6 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="37%"> <p class="MsoNormal">60A</p> </td> </tr> <tr> <td style="width: 62.16%; border: solid #4BACC6 1.0pt; border-right: solid #009EB8 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="62%"> <p class="MsoNormal">ICC-TDC</p> </td> <td style="width: 37.84%; border: solid #4BACC6 1.0pt; border-left: none; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="37%"> <p class="MsoNormal">55A</p> </td> </tr> <tr> <td style="width: 62.16%; border-top: none; border-left: solid #4BACC6 1.0pt; border-bottom: none; border-right: solid #009EB8 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="62%"> <p class="MsoNormal">负载线</p> </td> <td style="width: 37.84%; border: none; border-right: solid #4BACC6 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="37%"> <p class="MsoNormal">1.5mΩ</p> </td> </tr> <tr> <td style="width: 62.16%; border: solid #4BACC6 1.0pt; border-right: solid #009EB8 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="62%"> <p class="MsoNormal">快速电压回转率</p> </td> <td style="width: 37.84%; border: solid #4BACC6 1.0pt; border-left: none; padding: 0cm 5.4pt 0cm 5.4pt" valign="top" width="37%"> <p class="MsoNormal">12.5mV/µs</p> </td> </tr> <tr style="height: 13.5pt"> <td style="width: 62.16%; border-top: none; border-left: solid #4BACC6 1.0pt; border-bottom: solid #4BACC6 1.0pt; border-right: solid #009EB8 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt; height: 13.5pt" valign="top" width="62%"> <p class="MsoNormal">最大开关频率</p> </td> <td style="width: 37.84%; border-top: none; border-left: none; border-bottom: solid #4BACC6 1.0pt; border-right: solid #4BACC6 1.0pt; padding: 0cm 5.4pt 0cm 5.4pt; height: 13.5pt" valign="top" width="37%"> <p class="MsoNormal">300kHz</p> </td> </tr> </table> </div> <p>在 Shark Bay VRTB 桌上型平台指南中,输出滤波器的设计需求如下所示:</p> <p>输出电感:360nH/0.72mΩ <br>输出大型电容:560µF/2.5V/5mΩ(max) 4 至 5 个 <br>输出陶瓷电容:22µF / 0805 (在上层最多可放 18 个) <br><br></p> <p>步骤1:决定电感的参数</p> <p>决定电感值。<br>输出电感:360nH/0.72mΩ<br>决定DCR温度系数,TC<sub>DCR</sub>。<br>TC<sub>DCR</sub> = 3930ppm <br>因此,受温度影响的电感 DCR值,可由式(2)算出。下面的计算范例是 60°C 的 DCR 值。</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image012_zh-cn.jpg"> <img id="圖片 21" alt="Technical Document Image Preview" height="33" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image012_zh-cn.jpg" width="365"></a><br> <br></p> <p>步骤2:决定热补偿的NTC参数</p> <p>选用型号 NCP15WL104J03RC 的 NTC热敏电阻;该电阻值为100kΩ,且 β 值是 4485。利用式(6),可以计算在不同温度下的 NTC 电阻值;NTC热敏电阻操作于 60°C 时,其电阻值可计算如下:</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image013_zh-cn.jpg"> <img id="圖片 22" alt="Technical Document Image Preview" height="35" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image013_zh-cn.jpg" width="300"></a><br> <br></p> <p>步骤3:设计 DCR 电流检测网络及 R<sub>x</sub>、R<sub>s</sub> 和 R<sub>sum</sub> 之值</p> <p>如何决定 DCR 电流检测网络中之电容 C<sub>x</sub> 及电阻 R<sub>x</sub> 和 R<sub>s</sub> ,可参阅应用须知AN033 「不同DCR电流检测架构之比较」。<br>C<sub>x</sub> = 1µF, R<sub>s</sub> = 3.41kΩ, and R<sub>x</sub> = 590Ω <br>在RT8893,R<sub>sum</sub> 和 (R<sub>x</sub>+R<sub>s</sub>) 之比值必须设为4,才能有正常的操作。<br>R<sub>sum</sub> = 4•(R<sub>x</sub>+R<sub>s</sub>) = 16kΩ <br><br></p> <p>步骤4:设计R<sub>sum</sub> 之电阻网络</p> <p>选定三个作温度补偿之温度点。<br>选择(TH,TR,TL)=(100,60,20)<br>例如,R<sub>sum</sub> 在 60°C 下的值可由式(7)获得:</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image014_zh-cn.jpg"> <img id="圖片 17" alt="Technical Document Image Preview" height="41" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image014_zh-cn.jpg" width="372"></a></p> <p>因此,参数α<sub>1</sub>,α<sub>2</sub>,及Κ<sub>R</sub>可以计算如下:</p> <p> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image015_zh-cn.jpg"> <img id="圖片 19" alt="Technical Document Image Preview" height="171" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image015_zh-cn.jpg" width="405"></a></p> <p class="MsoNormal">再藉由公式(9),(10),和(11),可因此而算出R<sub>sump</sub>,R<sub>sums2</sub>和R<sub>sums1</sub>。</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image016_zh-cn.jpg"> <img id="圖片 24" alt="Technical Document Image Preview" height="125" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image016_zh-cn.jpg" width="386"></a></p> <p class="MsoNormal"><br><br></p> <h2 id="__Bookmark__5">5. 实验结果</h2> <p>图五显示了有 DCR 温度补偿之 DCLL 和 DIMON 回报结果。从实验结果来看,DCLL和DIMON回报结果都在容忍范围内。然而,若无 DCR 温度补偿,则在重载条件下,DIMON 回报结果会是高估的,因而造成 DCLL 会无法满足负载线规格,见图六。</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image017_zh-cn.gif"> <img id="圖片 50" alt="Technical Document Image Preview" height="262" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image017_zh-cn.gif" width="415"></a></p> <p class="MsoNormal">(a) DCLL </p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image018_zh-cn.jpg"> <img id="圖片 51" alt="Technical Document Image Preview" height="250" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image018_zh-cn.jpg" width="399"></a></p> <p class="MsoNormal">(b)DIMON 回报<br>图五、有 DCR 温度补偿之 DCLL 和 DIMON 回报结果</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image019_zh-cn.jpg"> <img id="圖片 52" alt="Technical Document Image Preview" height="255" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image019_zh-cn.jpg" width="407"></a></p> <p class="MsoNormal">(a) DCLL </p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image020_zh-cn.jpg"> <img id="圖片 53" alt="Technical Document Image Preview" height="257" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image020_zh-cn.jpg" width="410"></a></p> <p class="MsoNormal">(b)DIMON 回报<br>图六、无DCR温度补偿之 DCLL 和 DIMON 报告结果<br><br> </p> <h2 id="__Bookmark__6">6. 结论</h2> <p>本应用须知提供了DCR温度补偿电路的设计方法及实用的设计公式;经由适当的设计,它可以有效地减少因温度变化而对 DCR 值产生的影响,因此能在 DCR 电流检测应用中,提供正确的电流讯息。</p> <p class="MsoNormal"><br><br></p> <h2 id="__Bookmark__7">7. 参考数据</h2> <p>[1] 立锜科技 RT8884B 规格书。<br>[2] 立锜科技 RT8893 规格书。<br>[3] Intel, VR12.5 Pulse Width Modulation (PWM) 规格<br>[4] 立锜科技之应用须知AN033 「不同DCR电流检测架构之比较」。</p> <p class="MsoNormal"><br><br></p> <h2 id="__Bookmark__8">附录I. DCR温度补偿网络之公式推导</h2> <p>将三个温度点(TL,TR,TH)都代入式(8),即可得式(12)至式(14)。而式(15)和式(16)可分别由式(12)- 式(13)和式(13)- 式(14)得出。</p> <p> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image021_zh-cn.jpg"> <img id="圖片 25" alt="Technical Document Image Preview" height="311" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image021_zh-cn.jpg" width="506"></a></p> <p>定义 k<sub>R</sub>=R<sub>sump</sub>+R<sub>sums2</sub>,则可进一步将式(15)和式(16)表示为式(17)和式(18)。</p> <p> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image022_zh-cn.jpg"> <img id="圖片 26" alt="Technical Document Image Preview" height="272" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image022_zh-cn.jpg" width="619"></a></p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image023_zh-cn.jpg"> <img id="圖片 27" alt="Technical Document Image Preview" height="274" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image023_zh-cn.jpg" width="631"></a></p> <p>式(19)可由式(18)/ 式(17)导出。</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image024_zh-cn.jpg"> <img id="圖片 28" alt="Technical Document Image Preview" height="170" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image024_zh-cn.jpg" width="469"></a></p> <p>从式(18),可得R<sub>sump</sub>,如式(20)。</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image025_zh-cn.jpg"> <img id="圖片 29" alt="Technical Document Image Preview" height="61" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image025_zh-cn.jpg" width="471"></a></p> <p>然后,可得 R<sub>sums2</sub>,如式(21)。</p> <p> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image026_zh-cn.jpg"> <img id="圖片 30" alt="Technical Document Image Preview" height="71" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image026_zh-cn.jpg" width="467"></a></p> <p>R<sub>sums1</sub>可因此推导而得,如式(22)。</p> <p class="MsoNormal"> <a class="fancybox" href="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image027_zh-cn.jpg"> <img id="圖片 31" alt="Technical Document Image Preview" height="113" src="/content/dam/richtek-eds/resources/application-notes/an026/html-images-zh_cn/image027_zh-cn.jpg" width="466"></a></p> <p class="MsoNormal"><br><br></p> <div> <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 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 auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> 立锜科技电子报 </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 auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> <a class="link" href="http://www.richtek.com/My%20Richtek/Newsletters" target="_blank">订阅立锜科技电子报</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 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 auto; padding-right: 5pt; padding-left: 5pt; height: 17pt;"> <a class="link" href="http://www.richtek.com/Design%20Support/Technical%20Document/~/media/AN%20PDF/AN026_CN.ashx">PDF 下载</a> </td> </tr> </tbody> </table> </div> <p class="MsoNormal"><br><br></p> </div>
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