【经验】USB转UART接口器件CP2102N在使用过程中的过流保护

时间： 2022-03-09 来源：世强

技术问答

笔者参与开发的项目中使用USB转UART接口器件 CP2102N作为USB转串口的处理芯片，用于实现上位机USB与电路板串口TTL的通信功能，但是在使用过程中易出现由于误操作造成电源与地短路烧坏芯片的问题。通过在电源输入端加入一个LITTELFUSE 自恢复保险丝 1210L050，实现过流保护的功能。并且1210L050电路简单，只需要串入电源输入端，器件成本较低。

其中自恢复保险丝在USB转串口调试电路板中的位置如下：

图1 原理图

从原理图上也可以看到，解决CP2102N由于误操作导致短路的问题，只需要在电源的输入端串入一个自恢复保险丝。其中Littelfuse自恢复保险丝1210L050相关参数如下：

图2保险丝参数

保险丝的保持电流是0.5A，与常规USB输出的最大电流一致。1210L050的动作电流是1A，当短路造成瞬间电流过大就会断开电源的输入。其中两个器件在PCB上的图片如下图所示：

图3 PCB图片

图4 芯片局部特写

为了进一步验证短路保护的功能，用示波器探头测量电源经过自恢复保险丝的测试点，并将数字电流表串入电源输入端。手动将板子上5V电压与地电路，观察电压的波形如下：

图5 电压测量

从测试波形可以看出短路时由于自恢复保险丝的过流保护会断开电源的输入，此时测量的电压就是低电平；当短路动作撤销时就会恢复通路状态保证电源的输入。反复多次测量后电压无异常，芯片的通信功能也正常。

本文主要描述了通过使用Littelfuse自恢复保险丝1210L050解决了CP2102N使用过程中由于误操作造成的电源对地短路，造成烧毁芯片的问题。该方案具有电路简单，成本低的优势；以上几点大家使用过程中可供参考。

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Littelfuse（力特）正温度系数（PTC）热敏电阻选型指南

目录- 特性和术语应用和电路保护典型设计选择工作表表面贴装型径向引线型轴向引线型

型号- 30R135UU,72R300XF,1210L075/24PR,30R090UU,600R160-R1UR,1206L025YR,1812L,1812L350SL,1812L010/60DR,0603L050SLYR,2016L075/60,600R160-RAF,72R160XMR,0603L010YR,60R185XMR,1210L150TH,0805L110SLYR,16R1100G,1210L450SLWR,0402L050SLKR,0603L150SL,30R160UPR,1812L020PR,1206L110/12SL,2920L300DR,1206L175SLYR,72R090X,16R400GPR,16VT210SU,0805L260SLTH,1210L175WR,1812L200/12,LORHO,250S130¨CRCDR,30R300U,1812L200/16,16R1000GF,0805L100,16R250GU,20LR450,250R145-RA,2016L075/60MR,30R090,250R145-RAU,0402L020SL,2920L500/16,1206L260SLTHYR,1812L110/33MR,250S130¨CRC,250S130¨CRB,250S130¨CRA,16R135B,60R110XU,250S130V,2920L330/24MR,0603L075SL,0805L110,1206L175PR,250R145-RB,0603L,1206L012WR,16R500GU,24LT100,1812L150/12DR,1812L200/16DR,16R185BU,1210L380SL,600R160-RAUR,250S130¨CRBDR,30R800UH,15ST175U,250R145ZR,600R160F,16R1000G,16R110BPR,1206L380SLTHYR,16R250GPR,250R120-R3U,600R150-RA,600R150-RB,60R250,60R010,1812L075/33,250R120-R3,250R120-R2,250R120-R1,1210L200,1812L260/16MR,30R250UPR,72R135XMR,16R600GDR,1210L400SL,1206L300SLTHYR,30R700UMR,1206L450SL,250R120-RF,1206L200SLYR,250R120-RC,250R120-RA,0603L035YR,250R120-R2U,0603L175SL,1210L300SLYR,16R800GMR,60R375XH,16R110B,1812L190SLPR,16R1100GF,250R120TU,0805L075SLYR,16R1200G,250R120-RFZR,0402L,2920L200DR,2920L300,600R150F,2920L700SL,250R120-R1U,30R700UF,1210L075YR,2920L700SLPR,1210L110/16WR,60R110,1210L175SLYR,0805L010/24,16R600GU,2920L075/60MR,30R400U,60R050X,72R,60R,0402L010SLKR,72R090XPR,1206L050/15,1206L150SLYR,72R185XMR,2920L260PR,72R250XMR,1206L450SLWR,60R010XU,16VT210S,30R185,1812L075/24,1206L110SL,16R700GKLMR,1206L110TH,60R075X,LT SERIES,0603L100SLYR,1812L370SLPR,16R160BU,0805L110SL,60R025XPR,60R160X,0805L200SLTHYR,30R090UPR,2920L260/24,15LR380U,2920L,2920L185DR,16R500GPR,250R120T,60R090XPR,250R120U,30R300UU,1812L270SLPR,60R300X,1812L300SLPR,30R600U,72R075XU,0603L075SLYR,15LR260U,2016L,0402L020SLKR,06R075BU,06SL370GM,1206L075/16WR,1812L260SL,60R020XPR,20LR730,250R180MR,2920L330/24,06R155BPR,06SL190G,72R040XU,16R400G,1210L110THYR,2920L030DR,1812L160PR,2920L260/24DR,1812L075/33DR,1812L260TH,1210L035YR,1812L270SL,16R135BPR,1206L020YR,1206L075/13.2,30R250,0805L200SLTH,1812L050PR,600R150-RBF,0402L035SLKR,30R600UF,1210L350SL,16R300G,1206L075/13.6,72R075XPR,15LR260,15LR380,16R300GPR,30R185UPR,16R700GF,1812L014DR,60R160XMR,250R145U,0805L,1206L075SL,30R090U,2920L150DR,0805L050WR,1206L150TH,1812L200/12DR,0402L035SL,600R150-RAF,250R145T,1206L150SL,72R300XMR,1206L400SLWR,72R160XF,1812L150/24MR,30R500U,72R030XPR,2920L075DR,1206L075TH,1210L010WR,1812L350SLPR,LR,LT,1812L160/12DR,1812L150/24,60R025XU,2920L400/15MR,16R700GMR,0805L150SLYR,72R050XU,30R,16R1100GMR,60R010XPR,60R090,2920L200/24,1206L035YR,250R145-RBU,1206L050/15YR,16R800GF,1812L150/12,2920L400/15,VT SERIES,30R700U,1210L175SL,250R145TZR,0603L020YR,250S130¨CRADR,30R400UF,0805L300SL,1812L020/60,2016L050,1210L260SL,2016L050MR,16R250BU,1210L110/12WR,1812L010/60,06R120BPR,1812L075PR,30R400UMR,72R065XPR,60R135XF,SL SERIES,0805L010/24YR,16R250BPR,1812L370SL,30R160UU,20LR450U,0603L050SL,60R090X,1206L035/16,1210L020WR,1210L110/16,600R160-R1F,0402L010SL,250S130DR,60R185,24LT100U,72R020XPR,1206L150THWR,1210L380SLYR,1206L175SL,16R700GKL,72R300X,2920L050DR,2016L030,60R090XU,1210L110/12,2016L150,250R120ZR,16R185BPR,60R017XPR,1812L75/33,60R110XMR,1206L035/16YR,60R075XPR,60R025X,15ST175,250R180TMR,1812L150ZR,2920L050,1210L005WR,72R375X,1812L260THDR,1812L200THPR,72R050XPR,1812L125/16,12VL175XLU,0805L010YR,30R500UF,1812L75/24,16R700G,16R700GKLF,60R135X,2920L185,60R110X,1210L075,1812L160/12,16R900GF,1812L110,600R150-RBZR,600R,1812L125/6,60R040XPR,250R120-R1ZR,250R120-RFU,16R600G,2920L030,2920L150,30R800U,2016L100,1812L035/30DR,1812L075/24DR,16R135BU,250R120,30R185UU,SL,1812L010DR,2920L125PR,1206L200,1206L050YR,30R185U,ST,0603L150SLYR,1206L380SLTH,60R160XF,72R020X,30R600UMR,1812L300SL,60R050XU,0805L075SL,0805L260SLTHYR,72R250X,06SL370G,30R300,2016L075/060,1210L175,72R020XU,1812L260SLPR,250R180TF,16R1400GH,16R090BU,250R120-RAZR,0805L150SL,1812L050/30PR,30R160U,1210L260SLYR,60R065XPR,0805L020YR,1210L,1206L350SLTHYR,60R017X,1206L075SLYR,1206L110THYR,72R040XPR,2920L250DR,30R500,1210L110TH,1812L110/24DR,250R120-RCU,2016L200,0603L050YR,0805L300SLWR,1812L200,06R155BU,72R250XF,250R145,60R017XU,1812L020/60DR,1812L035/30,0603L050,1812L125/6PR,30R400,1206L400SL,60R030XPR,1210L350SLWR,60R300XF,VL,1206L260SLTH,06R120BU,72R065XU,1812L300MR,1210L400SLWR,VT,1210L450SL,16R,2920L500/16MR,1206L300SLTH,2920L075,250R120-RAU,72R030XU,250S130-RC,250S130-RB,16R110BU,250S130-RA,1812L300,2920L100PR,250S130,30R110UPR,30R250U,1206L110/12SLYR,0805L175SLYR,72R135X,0805L075WR,1206L016,16R500G,1206L150/12SL,0603L175SLYR,30R250UU,30R900U,16R900GMR,72R185XF,16R090B,1206L012,1206L075/13.2WR,600R150-RAZR,72R110X,1210L075/24,72R025X,0805L050,60R065XU,72R075X,1210L300SL,72R160X,0603L020,250R080ZR,72R090XU,1210L200SLYR,250R120TZR,60R185X,0603L025,0805L100WR,06R120B,2920L200/24DR,250R180,30R135U,60R040X,1206L025,06SL190GM,600R160-RA,72R135XF,06R075BPR,1206L020,1210L005,600R160UR,250R145-RBZR,12VL175XL,6

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