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目录
一,产品概述(General Description)  The JTM1489 is a wide input range step down DC/DC converrter from a high voltage input supplly.Opperating withh an input voltage rannge of 8V ～30V The JTM1489 achhieves 4.2A continuous output currennt with exxcellent loaad and linne reggulation. Thee synchronoous architeccture providees for highly efficcient designns. Constantt current annd connstant voltaage mode operation provide faast transient respoonse and eaases loop staabilization The JTM1489 features a dual-channneling CV/C moode control ffunctions. It operates in the Constant outtput Current mode or Constant ouutput Voltagge moode. The oveer current protection cuurrent value is sett by current sensing resisters. The JTM1489 requires a minimum number of reaadily availabble standarrd external componentts. Othher featuress include caable drop coompensation, andd thermal sh 二.产品特点(Features) ØWidee Input Voltaage Range: 8V ～ 30V ØUp too 93% Efficiency Ø No LLoop Compeensation Reqquired Ø Duall-channelingg CC/CV conntrol Ø Cablle drop Commpensation from 0Ω to 0.3Ω Ø Proggrammable CC Current Ø Therrmal Shutdoown Ø Overr current prootection Ø UVLO protectionn Ø Available in SOPP8-PP Package 三,应用范围 (Applications) Ø Car Charger / Addaptor Ø LED Driver Ø Pre-Regulator foor Linear Ree Ø Distrributed Power Systems Ø Batteery Chargerr 四.技术规格书下载（产品PDF）
 六.电路原理图  七,功能概述 Input Supply Voltage ...................................................................................................– 0.3V ～ 35V PDRI PIN Voltage.…………………………………………………………………………..– 0.3V ～ 35V EN, FB, NDRI Voltages............................................................ .... .... .... ..................... – 0.3V ～ 6V SW Voltage .......................................................................................................– 0.3V ～ (VIN + 1V) Operating Temperature Range(Note 2)…………………………………………….......–40℃ ～ +85℃ Junction Temperature…………………………………………………………………………..……+150℃ Storage Temperature Range................................................................................. – 65℃ ～ +150℃ Lead Temperature (Soldering, 10 sec)................................................................................... +265℃ 八JTM1489双路输出 2.4A 车载充电器应用指南 8.1应用电路  8.2简要说明 (1) 电路应用简单，外部元器件较少，系统成本低，可靠性高。 (2) 输出短路保护功能，内置过温保护，输入过压保护，过流保护可调，输出电流：Ics1=100mV/R2，Ics2=100mV/R3 输出带有线缆补偿功能：ΔVout(V) = R5(kΩ) · Iout(A)/2000 (3) 输入电压范围：8-30V DC。SOP-8 封装。 8.3DEMO 板 PCB 图  8.4DEMO 板测试  8.5 注意事项
（1）PCB 布局时 VIN，GND，SW，VOUT 等功率直线尽量要粗，短，直。
（2）FB 脚走线尽量远离 SW 信号，并且取样走线需要从输出电容正极接点取。外围最好使用地线包围。 （3）输入电容要靠近芯片 VIN 和 GND 引脚，输入地，输出地，芯片地线尽量靠近。 （4）外挂 NMOS 和 PMOS 引脚散热焊盘覆铜面积越大越好，以利散热。
8.6EMC 改善措施
（1）Layout：要保证功率环路面积小，地面积大，输入电容靠近芯片，SW 引线尽量短。（2）可在 SW 到地间加一个吸收电路：10 欧姆+1NF 来吸收开关尖峰。 九,相关芯片选择指南
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