LM2596-开关稳压电源
(5)12V直流电转3.3V稳压直流电的电路图及说明..
概述：LM2596系列开关电压调节器是降压型电源管理单片集成电路，能够输出3A的驱动电流，同时具有很好的线性和负载调节特性。
固定输出版本有3.3V、5V、12V，还有一个输出可调版本。
添加少量的外部元件就可以使用该电压调节器。
该器件内部集成有频率补偿和固定频率发生器。
开关频率为150KHz，与低频开关调节器相比较，可以使用更小规格的滤波元件。
其封装形式包括标准的5脚TO-220封装和5脚TO-263表贴封装。
由于该器件可以使用通用的标准电感，这更优化了LM2596的使用，极大地简化了开关电源电路的设计。
该器件还有其他一些特点：在特定的输入电压和输出负载的条件下，输出电压的误差可以保证在±4%的范围内，振荡频率误差在±15%的范围内；可以用仅80μA的待机电流，实现外部断电；具有自我保护电路（一个两级降频限流保护和一个在异常情况下断电的过温完全保护电路）。
特征：※ 3.3V、5V、12V的固定电压输出和可调电压输出※可调输出电压范围1.2V～37V，±4%※封装形式：TO-220（T）和TO-263（S）※保证输出负载电流3A※输入电压可高达40V※仅需4个外接元件※很好的线性和负载调节特性※150KHz固定频率的内部振荡器※TTL关断能力※低功耗待机模式，I Q的典型值为80μA※高转换效率※使用容易购买的标准电感※具有过热保护和限流保护功能应用：※简易高效率降压调节器※在卡上的开关电压调节器※正到负电压转换器专利号：5382918典型电路（固定输出电压版本）：封装和型号：※弯曲交叉的引脚，通孔封装，5脚TO-220 (T)订货型号：LM2596T-3.3, LM2596T-5.0,LM2596T-12 or LM2596T-ADJ ※表面贴封装，5脚TO-263 (S)订货型号：LM2596S-3.3, LM2596S-5.0, LM2596S-12 or LM2596S-ADJ极限条件：最大供电电压45VON /OFF 管脚输入电压-0.3≤V≤+25V反馈脚电压-0.3≤V≤+25V输出电压到地（稳态）-1V功率消耗内部限定储存温度-65°C 到+150°CESD易感性（人体模式）2KV焊接温度T封装(锡焊, 10秒) +260°C最大结温+150°C运行条件：温度范围－40°C≤T J≤+125°C供电电压 4.5V 到40VLM2596-3.3电参数说明：标准字体对应的项目适合于TJ=25℃时，粗体字对应的项目适合于全温度范围符号意义测试条件典型值(注3)极限值(注4)单位(极限)系统参数(注5) 测试电路图 1V OUT输出电压 4.75V ≤ V IN≤ 40V,0.2A ≤ I LOAD≤ 3A 3.33.168/3.1353.432/3.465VV(min)V(max)η效率V IN = 12V,I LOAD = 3A73 %LM2596-5.0电参数说明：标准字体对应的项目适合于TJ=25℃时，粗体字对应的项目适合于全温度范围符号意义测试条件典型值(注3)极限值(注4)单位(极限)系统参数(注5) 测试电路图 1V OUT输出电压7V ≤ V IN ≤ 40V,0.2A ≤ I LOAD≤ 3A 5.04.800/4.7505.200/5.250VV(min)V(max)η效率V IN = 12V,I LOAD = 3A80 %LM2596-12电参数说明：标准字体对应的项目适合于TJ=25℃时，粗体字对应的项目适合于全温度范围符号意义测试条件典型值(注3)极限值(注4)单位(极限)系统参数(注5) 测试电路图 1V OUT输出电压15V ≤ V IN≤ 40V,0.2A ≤ I LOAD≤ 3A 12.011.52/11.4012.48/12.60VV(min)V(max)η效率V IN = 25V,I LOAD = 3A90 %LM2596-ADJ电参数说明：标准字体对应的项目适合于TJ=25℃时，粗体字对应的项目适合于全温度范围符号意义测试条件典型值(注3)极限值(注4)单位(极限)系统参数(注5) 测试电路图 1V FB反馈电压 4.5V ≤ V IN≤ 40V,0.2A ≤ I LOAD≤ 3AV OUT设计为3V，电路图 1 1.2301.193/1.1801.267/1.280VV(min)V(max)η效率V IN = 12V, V OUT =3V, I LOAD = 3A73 %所有输出电压版本电参数说明：标准字体对应的项目适合于TJ=25℃时，带下划线的粗斜体字对应的项目适合于整个温度范围。
开关电源稳压控制器
R2=R1(
VOUT － 1) VREF
VREF=1.23V 为了使电路稳定/选 R1 阻值为 1K，误差精度为 1%。 CIN —470μF 50V COUT —220μF 35V （Nichicon PL 系列铝电解电容） R1 —1KΩ，1%。 D1 —5A 40V IN5825（肖特基整流二极管） L1 —68μH CFF —参照应用说明 注 1：反馈线要远离电感，电路中的粗线一定要短，最好用地线屏蔽 注 2：R2 应尽量靠近反馈脚
特点
※ ※ ※ ※ ※ ※ ※ ※ ※ ※ 3.3V、5V、12V 固定输出版和输出可调版 负载电流达到 3A 输入电压达到 40V 外围只需四个元件 电压调整率和电流调整率非常小 内置固定频率为 150kHz 的振荡器 TTL 电平关断功能 待机电流仅为 75μA 转换效率高 内置过热保护电路和限流保护电路
AE2596 (LM2596)技术说明书
管脚图
5-Lead TO-220 (T) 5-Lead TO-263 (S)
1,3,5 2,4
5 4 3 2 1
5 4 3 2 1
管脚设置
序号 管脚符号 说明 1 VIN 直流输入 2 Output 直流输出 3 GND 电源地 4 Feedback 反馈端 使能端 5
应用领域 ※ 高效降压型调节器 ※ 在线式开关调节器 ※ 负电压转换器 典型应用图(固定电压输出模式)
Feedback
DC12V
+Vin
Cin 680uF
1
AE2596
5.0
4
Output
L1 33uH D1 IN5824
5.0V
2 3
GND
5
ON/OFF
LM2596中文资料
LM2596S-3.3, LM2596S-5.0,LM2596S-12， LM2596S-ADJ为TO-263封装（SMT）。
η
效率
VIN=12V，ILOAD=3A
73
LM2596□—5.0 （见注 14）
VOUT
输出电压
5.0 7V≤VIN≤40V， 0.2A≤ILOAD≤3A
η
效率
VIN=12V，ILOAD=3A
80
3.168/3.135 3.432/3.465
V V（min） V（max） %
4.800/4.750 5.200/5.250
2 30
A A(min) A(max) μA(max) mA mA(max)
IQ
静电流
见注 9
5 10
mA mA(max)
ISTBY
待机静电流
ON/OFF 脚=5V（OFF）（9）
80
μA
200/250
μA(max) ３
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LM2596 开关电压调节器 SEPTEMBER， 2004
ILOAD=500mA。 （见注 14）
361 符号
参量
cu 器件参数
.m Ib
反馈偏置电流
wwwfO
振荡器频率
条件
LM2596□—XX
典型值（2） 极限值（3）
单位
只适用于输出可调节的情况，VFB=1.3V
lm2596中文资料
VIN=25V，VOUT =3V， ILOAD=3A
η
效率
VIN=25V，VOUT =15V，ILOAD=3A
电气特性（所有输出）
典型值（2） 极限值（3）
单位
12.0
88 1.230
73 90
11.52/11.40 12.48/12.60
V V（min） V（max） %
1.193/1.180 1.267/1.280
2000
V
气流焊（60 秒）
215
℃
焊接时的管脚
TO-263
温度
红外线焊接（10 秒）
245
℃
TO-220
波峰焊/电烙铁焊接（10 秒）
260
℃
最高结温
150
℃
工 作条 件
温度范围 电源电压
-40～125
℃
4.5～40
V
注 1：人体放电模式相当于一个 100PF 的电容通过一个 1.5K 的电阻向每个管脚放电。
电气特性
说明：标准字体对应的项目适合于 TJ=25℃时，带下划线的粗斜体字对应的项目适合于整个温度范围； 系统参量(4) 测试电路见图 1
符号
参量
条件
典型值（2）
极限值（3）
单位
LM2596□—3.3 （见注 14）
VOUT
输出电压
3.3 4.75V≤VIN≤40V，
0.2A≤ILOAD≤3A
η
效率
A(max)
50
μA(max)
2 30
mA mA(max)
5 10
mA mA(max)
80
μA
200/250
μA(max) ˏ
LM2596开关电源 多路开关电源 DC-DC降压电源 固定可调输出 原理图和PCB
LM2596开关电源多路开关电源DC-DC降压电源固定/可调输出原理图和PCB基本原理开关电源的基本原理就不做赘述，有兴趣的可以看下我们TPS5430正负电源的原理简介即可。
芯片选型LM2596最大负载电流能到3A，有多个规格可选，3.3V、5V、12V以及可调输出等，ADJ输出范围是1.2V到Vin-1V，最大可支持40V输入，也有特殊规格比如LM2596-HVS，可达60V 的输入的电压，但是容易买到假芯片。
这个大家都懂的。
我们可以大致看出芯片的价格相对比较便宜，所以在普通使用场合，该芯片的性价比还是可以的。
原理图&3D-PCB在原理图方面基本没有这个特别介绍，主要是布局以及PCB布线的讲解。
具体讲解1、原理图需要注意电容以及二极管的方向，至于耐压、封装以及选型问题可以参考TPS5430开关电源分析。
2、这边截取了一路的布局以及走线作为示意。
首先C10和C12为电源输入滤波，应该尽量靠近芯片输入端，其次是输入的线应该尽量的粗，才能满足大电流。
3、芯片的第5脚是GND脚，需要在旁边放两个接地的过孔，这样有利于电流的释放接入背面的GND平面。
4、由于输出电流大是芯片发热就会比较厉害，所以在芯片散热焊盘的地方打了12个过孔方便散热。
5、其次是在接近输出端子的地方加一个C16电容可以进一步的减小纹波。
6、需要特别注意的是D5二极管为整流二极管，正向端接GND必须要良好接地，也就是需要过孔或者较粗的线接到输入电源的GND。
模块原理图-PDF、原理图库、PCB库下载以下为原文地址，https:///Elecdemo/article/details/103276839下载需要积分，仅供参考。
官方网址。
LM2596芯片简介
编辑本段LM2596芯片简介LM2596系列是美国国家半导体公司生产的3A电流输出降压开关型集成稳压芯片，它内含固定频率振荡器（150KHZ），和基准稳压器（1.23v），并具有完善的保护电路：电流限制、热关断电路等。
利用该器件只需极少的外围器件便可构成高效稳压电路。
提供有：3.3V、5V、12V及可调（-ADJ）等多个电压档次产品。
此外，该芯片还提供了工作状态的外部控制引脚。
LM2596芯片LM2596系列开关稳压集成电路的主要特性如下：1、最大输出电流：3A2、最高输入电压：40V3、输出电压：3.3V、5V、12V及（ADJ）等，最大输出电压37V4、震荡频率：150KHZ5、转换效率：75%~88%（不同电压输出时的转换效率不同）6、工作温度范围：-40℃~+125℃7、工作模式：低功耗/正常两种模式。
可外部控制8、工作模式控制：TTL电平相容9、所需外部组件：仅四个（不可调）；六个（可调）10、器件保护：热关断及电流限制11、封装形式：5脚（TO-220(T)；TO-263(S))编辑本段LM2596内部框图LM2596芯片内部框图。
注：此图为TO-220封装形式的内部框图。
LM2596内部包含150KHZ振荡器、1.23v基准稳压电路、热关断电路、电流限制电路、放大器、比较器和内部[1]稳压电路等。
为了产生不同的输出电压通常将比较器的负端接基准电压（1.23V ），正端接分压电阻网络。
其中R1=1KΩ，R2分别为1.7KΩ（3.3v），3.1KΩ（5V），8.8KΩ（12V）、0（-ADJ）。
将输出电压的分压电阻网络的输出同内部基准稳压值1.23V进行比较，若电压有偏差，则可用放大器控制内部振荡器的输出占空比，从而使输出电压保持稳定。
编辑本段LM2596经典应用实例具体应用时可根据需要选择：LM2596-5V、LM2596-3.3等。
要获得+1.8V、+5V输出电压时请选用A图，要获得+3.3V输出电压时请选用B图。
lm2596中文资料
VFB
反馈电压
0.2A≤ILOAD≤3A
VOUT 调为 3V， 电路图见图 1
η
效率
VIN=25V，VOUT =3V， ILOAD=3A
VIN=25V，VOUT =15V，ILOAD=3A
电气特性（所有输出）
典型值（2） 极限值（3）
单位
12.0
88 1.230
73 90
11.52/11.40 12.48/12.60
特点
※ 3.3V、5V、12V 的固定电压输出和可调电压输出 ※ 可调输出电压范围 1.2V～37V±4% ※ 输出线性好且负载可调节 ※ 输出电流可高达 3A ※ 输入电压可高达 40V ※ 采用 150KHz 的内部振荡频率，属于第二代开关电压调节器，功耗小、效率高 ※ 低功耗待机模式，IQ 的典型值为 80μA ※ TTL 断电能力 ※ 具有过热保护和限流保护功能 ※ 封装形式：TO-220（T）和 TO-263（S） ※ 外围电路简单，仅需 4 个外接元件， 且使用容易购买的标准电感
５
TO-263 封装（S）尺寸图
单位：英寸/毫米
TO-220 封装（T）尺寸图
单位：英寸/毫米
６
设计步骤及实例
固定输出调节器的设计步骤
条件：VOUT=3.3（或 5 、或 12）V , VIN（max）为最大直流输入电压, ILOAD（max）为最大负载电流 步骤： 1. 电感的选择（L1） A． 要根据图 4、图 5 和图 6 所示的数据选择电感的适当值（分别对应输出电压为 3.3V、5V 和 12V），对于所有的
符号
参量
器件参数
Ib
反馈偏置电流
fO
振荡器频率
VSAT
lm2596-3.3__LM2596-ADJ_LM2596-12_LV2596-3.3_中文资料
见注 9
5 10
mA mA(max)
ISTBY
待机静电流
ON/OFF 脚=5V（OFF）（9）
80
μA
200/250
μA(max)
３
符号
参量
条件
θJC
θJA
θJA
热阻
θJA
θJA
ON/OFF 控制 （ 测试电路见图 1）
TO-220 或 TO-263 TO-263（10） TO-263（11） TO-263（12） TO-263（13）
V V(max)
最大工作周期（ON） DC
最小工作周期(OFF）
见注 7 见注 8
100
%
0
%
ICL
极限电流
峰值电流（6，7）
4.5 3.6/3.4
A A(min)
6.9/7.5
A(max)
输出为 0V（6，8）
50
μA(max)
IL
输出漏电流
输出为-1V（9）
2 30
mA mA(max)
IQ
静电流
特点
※ 3.3V、5V、12V 的固定电压输出和可调电压输出 ※ 可调输出电压范围 1.2V～37V±4% ※ 输出线性好且负载可调节 ※ 输出电流可高达 3A ※ 输入电压可高达 40V ※ 采用 150KHz 的内部振荡频率，属于第二代开关电压调节器，功耗小、效率高 ※ 低功耗待机模式，IQ 的典型值为 80μA ※ TTL 断电能力 ※ 具有过热保护和限流保护功能 ※ 封装形式：TO-220（T）和 TO-263（S） ※ 外围电路简单，仅需 4 个外接元件， 且使用容易购买的标准电感
ON/OFF 脚逻辑输入
LM2596 DC_DC
本作品驱动6舵机和直流电及多个模块，输出电流很大，耗电量也大。
一般的7805稳压电路根本就不能驱动。
最终方案采用可充电式锂电池作为主电源，再选用四个基于LM2596 的DC-DC模块来供电。
采用此种供电方式效率高且输出的电压很稳定，有效为各个模块提供电压。
为了使舵机更有力地操作，我们选用LM2596-调压到6v控制。
LM2596-adj使用原理：
如上图所示：有V o=Vref(1+R2/R1)
当Vref=1.23V
有R2=R1（Vo/Vref-1）
其中Vref为DC/DC开关稳压器内部自带的基准电压或者用户外接的基准电压，R1、R2构成输出电压采样电路，用于设置输出电压的大小。
当输出电压Vout因负载变化而变化时，反馈电压Vf也随着变化，DC/DC稳压器内部的控制电路根据反馈电压Vf（采样电压）与Vref 差值的大小来适当调整功率变换电路的控制参数（如PWM的占空比等），使输出电压稳定在一个固定的值，达到稳压的目的。
恒流源和恒压源在电路上的差别反应在两者的采样电路采集的对象不一样。
恒压源为了保持输出电压的恒定，需要实时对输出电压跟踪、控制，在负载变化的情况下使输出电压不随负载的变化而变化，而恒流源是指在负载变化的情况下，稳压器能根据负载的变化相应调整输出电压，保持输出电流不变，恒流源采样电路采集的是输出的电流信号，但实际上采集的是经过I/V转换后反应电流大小的电压信号，因此，把输出的电流信号转换成电压信号，输入到DC/DC 开关稳压器的反馈引脚，就能实现恒压源到恒流源的转变。
所以适当调节R2，可以调节输出电压。
LM2596全中文资料
LM2596全中文资料随着电子技术的发展，各种电子设备越来越多，而其中一个重要的电源管理模块就是开关电源。
在电子设备中，开关电源起着将交流电转换为直流电的作用，提供稳定可靠的电力供应。
而LM2596是一种常见的开关稳压模块，它被广泛应用于各种电子设备中，提供高效、稳定的电源管理解决方案。
LM2596是一款具有高效率、低功耗和稳定性的降压型开关稳压模块。
它能够将输入电压转换为相对稳定的输出电压，通常被用于降低电源电压供应至微控制器、电路板、传感器等部件。
同时，LM2596还具备短路保护、过热保护等功能，以确保电子设备的安全运行。
LM2596采用了开关型调制控制技术，能够在不同负载情况下自动调整开关频率和占空比，以保持输出电压稳定。
它的输入电压范围广，可以适应不同的电源输入，包括交流电和直流电。
而输出电压可通过外部电阻分压调整，从而满足不同电子设备的需求。
除了稳压功能，LM2596还具备过流保护功能。
当电流超过设定值时，它会自动切断输出，避免因电流过大而损坏电子设备。
同时，LM2596还配备了过热保护功能，当温度超过一定范围时，它会自动降低工作频率或停止工作，以防止过热引起故障。
LM2596作为一种常见的开关稳压模块，其技术参数和应用案例都有详尽的中文资料可供参考。
对于初学者而言，这些资料不仅提供了LM2596的基本工作原理和使用方法，还介绍了它在各种电子设备中的具体应用场景和性能要求。
其中，电路图、元器件清单和详细的步骤说明，使得初学者能够更好地理解和使用LM2596。
此外，还有一些中文论坛和社区提供了关于LM2596的技术讨论和使用心得的帖子。
这些帖子通常包含了实际应用中遇到的问题和解决方案，对于学习和掌握LM2596的使用具有很大帮助。
在这些中文论坛中，你可以与其他电子爱好者交流经验，共同探讨LM2596的使用技巧。
综上所述，LM2596作为一种常见的开关稳压模块，提供了高效、稳定的电源管理解决方案。
LM2596开关电源调节器(中文)
A(max) μA(max)
2
mA
30
mA(max)
5
mA
10 80
mA(max) μA
200/250
μA(max) ３
电子发烧友 电子技术论坛
LM2596 开关电压调节器 SEPTEMBER， 2004
管脚图
极限参数
名称
范围
最大电源电压
45
脚输入电压
-0.3～25
“反馈”脚电压
-0.3～25
到地的输出电压（静态）
-1
功耗
由内部限定
储存温度
-65～150
静电释放（人体放电 1）
2000
气流焊（60 秒）
215
焊接时的管脚
TO-263
红外线焊接（10 秒）
245
温度
TO-220
波峰焊/电烙铁焊接（10 秒）
符号
参量
条件
典型值（2）
极限值（3）
单位
LM2596□—3.3 （见注 14）
VOUT
输出电压
3.3 4.75V≤VIN≤40V，
0.2A≤ILOAD≤3A
η
效率
VIN=12V，ILOAD=3A
Байду номын сангаас73
LM2596□—5.0 （见注 14）
VOUT
输出电压
5.0 7V≤VIN≤40V， 0.2A≤ILOAD≤3A
特点
※ 3.3V、5V、12V 的固定电压输出和可调电压输出 ※ 可调输出电压范围 1.2V～37V±4% ※ 输出线性好且负载可调节 ※ 输出电流可高达 3A ※ 输入电压可高达 40V ※ 采用 150KHz 的内部振荡频率，属于第二代开关电压调节器，功耗小、效率高 ※ 低功耗待机模式，IQ 的典型值为 80μA ※ TTL 断电能力 ※ 具有过热保护和限流保护功能 ※ 封装形式：TO-220（T）和 TO-263（S） ※ 外围电路简单，仅需 4 个外接元件， 且使用容易购买的标准电感
LM2596S-ADJ DCDC电源管理芯片应用资料-奥伟斯
Switching Voltage RegulatorsFeatures∙ 3.3V, 5V, 12V, and adjustable output versions ∙ Adjustable version output voltage range, 1.2V to 37V ± 4% max over line and load conditions ∙ Guaranteed 3A output load current ∙ Input voltage range up to 40V ∙ Requires only 4 external components ∙ Excellent line and load regulation specifications ∙ 150kHz fixed frequency internal oscillator ∙ TTL shutdown capability ∙ Low power standby mode, I Q typically 100μA∙ Thermal shutdown and current limit protectionJM2596-xxTO-220-5LJM2596T-XXTO-263-5LJM2596S-XXORDERING INFORMATIONJM2596S-12 JM2596S-3.3 JM2596S-5.0 JM2596S-ADJ JM2596T-12 JM2596T-3.0 JM2596T-5.0 JM2596T-ADJFunctions∙ Simple high-efficiency step-down regulator ∙ On-card switching regulators ∙ Positive to negative converterDescriptionThe JM2596 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down switching regulator, capable of driving a 3A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V and an adjustable output version.Requiring a minimum number of external components, these regulators are simple to use.The JM2596 series operates at a switching frequency of 150kHz. Available in standard 5-lead TO-220 package.Other features include a guaranteed ± 4% tolerance on output voltage under specified input voltage and output load conditions, and ± 15% on the oscillator frequency. External shutdown is included, featuring typically 100μA standby current. Self protection features include a two stage frequency reducing current limit for output switch and an over temperature shutdown for completeprotection under fault conditions. The over temperature shutdown level is about 145o C with 5oC hysteresis.说明JM2596系列稳压器是单片集成电路，为降压开关稳压器提供所有的有源功能，能够以优良的线路和负载调节驱动3A负载。
LM2596构成的可调限流稳压器
LM2596构成的可调限流稳压器
LM2596简介
LM2596系列稳压芯片，是德州仪器（TI）生产的3A降压开关型稳压芯片。
LM2596性能特点：
•内含固定频率振荡器（150KHZ）和基准稳压器（1.23v）
•具有完善的保护电路、电流限制、热关断电路等
•仅需极少的外围器件便可构成高效稳压电路
•提供3.3V、5V、12V及可调（-ADJ）等多个电压档次
LM2596构成的可调限流稳压器
LM2596的常规应用，不具备电流限制功能，在一些电子设计和辅助设备上，对限流功能有一定的需求，虽然厂家给出的标准应用电路无法完成这一功能，我们可以通过适当的添加功能电路，让它实现限流功能。
如下图：
LM2596构成的可调限流稳压器
上图的功能网友已经验证过，出于严谨，小编在此不做工作原理的分析，‘机电匠’有机会对电路功能做验证实验的时候，再通过视频文章向大家呈现。
lm2596中文资料
lm2596中文资料1. 概述lm2596是一款高效率开关电源稳压器芯片，广泛应用于电子设备中对直流电压进行稳定调整的场合。
本文档将详细介绍lm2596的特性、工作原理、应用场景以及使用注意事项。
2. 特性•宽输入电压范围：4V-40V•可调输出电压范围：1.23V-37V•高效率：可达到92%•最大输出电流：3A•过热保护功能3. 工作原理lm2596采用了开关稳压器的工作原理，通过周期性地开关和断开电流流通路径，将输入电压转换为稳定的输出电压。
其主要原理如下：1.输入电压通过电感和开关管传导到输出端，同时电容储存能量。
2.控制器检测输出电压，如果低于设定值，则控制开关管开启，使电流通过电感传输到输出端，提供稳定的输出电压。
3.如果输出电压高于设定值，则控制开关管关闭，切断电流流动。
这种周期性的开关和断开电路，可以通过控制开关管的开启时间和关闭时间，来调整输出电压的稳定性和精确度。
4. 应用场景lm2596广泛应用于各种需要稳定直流电压的场合，以下是lm2596常见的应用场景：4.1 电子设备稳压电源lm2596可以根据需要调整输出电压，可以在电子设备中作为稳压电源芯片使用。
它可以将输入电压调整为稳定的输出电压，以供电子设备正常运行。
4.2 LED照明由于lm2596具有高效率和可调输出电压的特性，非常适合用于LED照明应用。
lm2596可以将输入电压调整为适合LED灯的电压，提供稳定的电源以驱动LED照明。
4.3 高频电源lm2596的高效率和宽输入电压范围，使其非常适合用于高频电源应用。
lm2596可以将输入电压转换为稳定的高频输出，满足高频电源的需求。
5. 使用注意事项在使用lm2596时，请注意以下事项：1.输入电压不要超过40V，否则可能导致芯片过载损坏。
2.充分考虑散热问题，尽量避免芯片过热，建议在芯片周围预留散热空间。
3.在使用lm2596时，应按照芯片的使用说明进行正确的电路设计和连接。
LM2596开关电压调节
2.0
V(min)
5
μA
15
μA(max)
0.02
μA
5
μA(max)
注 2： 典型值是指在 25℃下的数值，代表最常见的情况。 注 3： 所有的极限参数都必须适合于室温（用正常字体表示）和极限温度（用带下划线的粗斜体字表示），所有室
温下的极限参数都是经过测试得出的，所有的极限温度下的极限参数都可以通过使用相关的标准静态质量控 制方法来加以保证。 注 4：二极管、电感、输入和输出端的电容以及调节输出电压的电阻等外接元件可能会影响开关调节器的系统性 能。当 LM2596 用在如图 1 所示测试电路中时，其系统性能如电气特性中系统参量所示。 注 5：当第二级电流极限功能启动时，开关频率会有所下降， 下降的程度取决于过电流的严重程度。 注 6：输出管脚不连接电感、电容或二极管。 注 7：把反馈管脚和输出管脚断开，把反馈管脚连到 0V，以强制输出开关晶体管导通。 注 8：把反馈管脚和输出管脚断开，把反馈管脚连到 12V（当 VOUT=3.3V、5V 或 ADJ 时）或 15V（当 VOUT=12V 时）， 以强制输出开关晶体管截止。 注 9：VIN=40V 注 10：环境热阻（不外加散热片）是指 TO-220 封装的 LM2596 垂直焊接在覆盖有面积约为 1 平方英寸铜箔的 PCB 上所对应的值。 注 11：TO-263 封装的 LM2596 垂直焊接在覆盖有面积约为 0.5 平方英寸铜箔的单面 PCB 上所对应的环境热阻。 注 12：TO-263 封装的 LM2596 垂直焊接在覆盖有面积约为 2.5 平方英寸铜箔的单面 PCB 上所对应的环境热阻。 注 13：TO-263 封装的 LM2596 垂直焊接在覆盖有面积约为 3 平方英寸铜箔的双面 PCB 上所对应的环境热阻，而 PCB 的另一面覆盖有面积约为 16 平方英寸铜箔。 注14： LM2596T-3.3, LM2596T-5.0, LM2596T-12， LM2596T-ADJ为TO-220封装（DIP）； LM2596S-3.3, LM2596S-5.0,LM2596S-12， LM2596S-ADJ为TO-263封装（SMT）。
lm2596中文资料_数据手册_参数
中文资料 LM2596电源降压调整器
LM2596电源降压调整器（150KHz，3A）英文文章名：LM2596 SIMPLE SWITCHER® Power Converter 150 kHz3A Step-Down Voltage Regulator文章出处：版本号：DS012583 日期：2002年5月摘录人：黄明强摘录日期：2007年5月3日是否好买估计：生产中心正在使用价格：概述：LM2596系列开关电压调节器是降压型电源管理单片集成电路，能够输出3A的驱动电流，同时具有很好的线性和负载调节特性。
固定输出版本有3.3V、5V、12V，还有一个输出可调版本。
添加少量的外部元件就可以使用该电压调节器。
该器件内部集成有频率补偿和固定频率发生器。
开关频率为150KHz，与低频开关调节器相比较，可以使用更小规格的滤波元件。
其封装形式包括标准的5脚TO-220封装和5脚TO-263表贴封装。
由于该器件可以使用通用的标准电感，这更优化了LM2596的使用，极大地简化了开关电源电路的设计。
该器件还有其他一些特点：在特定的输入电压和输出负载的条件下，输出电压的误差可以保证在±4%的范围内，振荡频率误差在±15%的范围内；可以用仅80μA的待机电流，实现外部断电；具有自我保护电路（一个两级降频限流保护和一个在异常情况下断电的过温完全保护电路）。
特征：※ 3.3V、5V、12V的固定电压输出和可调电压输出※可调输出电压范围1.2V～37V，±4%※封装形式：TO-220（T）和TO-263（S）※保证输出负载电流3A※输入电压可高达40V※仅需4个外接元件※很好的线性和负载调节特性※150KHz固定频率的内部振荡器※TTL关断能力※低功耗待机模式，I Q的典型值为80μA※高转换效率※使用容易购买的标准电感※具有过热保护和限流保护功能应用：※简易高效率降压调节器※在卡上的开关电压调节器※正到负电压转换器专利号：5382918典型电路（固定输出电压版本）：封装和型号：※弯曲交叉的引脚，通孔封装，5脚TO-220 (T)订货型号：LM2596T-3.3, LM2596T-5.0,LM2596T-12 or LM2596T-ADJ ※表面贴封装，5脚TO-263 (S)订货型号：LM2596S-3.3, LM2596S-5.0, LM2596S-12 or LM2596S-ADJ 极限条件：最大供电电压45VON /OFF 管脚输入电压-0.3≤V≤+25V反馈脚电压-0.3≤V≤+25V输出电压到地（稳态）-1V功率消耗内部限定储存温度-65°C 到+150°CESD易感性（人体模式）2KV焊接温度T封装(锡焊, 10秒) +260°C最大结温+150°C运行条件：温度范围－40°C≤T J≤+125°C供电电压 4.5V 到40VLM2596-3.3电参数说明：标准字体对应的项目适合于TJ=25℃时，粗体字对应的项目适合于全温度范围LM2596-5.0电参数说明：标准字体对应的项目适合于TJ=25℃时，粗体字对应的项目适合于全温度范围LM2596-12电参数所有输出电压版本电参数说明：标准字体对应的项目适合于TJ=25℃时，带下划线的粗斜体字对应的项目适合于整个温度范围。
LM2596降压电源实测记录
用LM2596自己制作稳压电源过程记录由于本人需要一个28V降到12V和一个28V降到5V，电流在2A左右的二个电源。
为了方便先在淘宝上买了二块做好的，价格便宜，才10元一块。
但是没用多久，就坏了。
本人估计可能是模块用的芯片不好，而我又是24小时连续使用。
所以决定自己做二个试试一：选择元件，都在淘宝上购买，选NS全新进口的LM2596T-12,二块。
LM2595T-5,二块。
输入电容用全新进口黑金刚63V1000UF,输出电容买了220UF,330UF,470UF,耐压35V,50V,63V.买了多种好测试时用。
电感买环型磁芯最大电流3A的9X12尺寸的33UH,47UH,68UH多个。
二极管用MBR2060CT耐压60V电流20A肖特基快速整流二极管，够大的。
线路接线如下：由于接线比较简单，很快就搞定了，现开始测试电路。
先测试12V输出的：元件参数：CIN,1000UF,COUT330UF,L1,33UH.由于本人只是业余制作，只有数字万用表二台，只能测试电流，电压。
负载用12V的白炽灯泡，输入电压输入电流输入功率输出电压输出电流输出功率效率37V 0.684A 25.308W 12V 1.77A 21.24W 84%25V 0.428A 10.7W 12V 0.735A 8.82W 83%24.5V 1.335A 32.7W 11.9V 2.39A 28.44W 87%输出5V的测试：元件，CIN1000UF,COUT330UF,L1,33UH.输入电压输入电流输入功率输出电压输出电流输出功率效率37V 0.222A 8.214W 5V 1.19A 5.95W 73%37V 0.407A 15.1W 5V 2.22A 11.1W 74%12V 1.161A 13.93W 4.99V 2.21A 11.03W 79%以上测试数据跟厂家给出的数据比较接近，整个电路还可以的，当把电流升到3A时，连续通电8小时左右，芯片基本上工作稳定。
lm2596升压电路原理
lm2596升压电路原理
LM2596升压电路的原理主要基于开关型电源的工作方式。
开关型电源通过控制开关管的开通和关断，将输入电压转换成脉冲电压，并通过变压器等元件升压或降压，最后输出稳定的直流电压。
LM2596是一个开关型电源管理芯片，其工作电压范围为至40V，最大输出电流为3A，可以提供可调的参考电压。
它内部集成了一个开关型电源控制器和一个具有开关功能的晶体管，可以方便地实现升压或降压电源转换。
在LM2596升压电路中，输入电压通过开关管加在电感器上，电感器产生反电势。
当开关管导通时，反电势为负值，输入电压与反电势相加，因此输入侧的电感常称升压电感。
当反电势与输入电压相加的值大于输出电压时，开关管继续保持导通状态，电感器继续储能。
当开关管关断时，电感器向负载释放能量，同时向电容充电。
通过控制开关管的导通和关断时间，可以得到稳定的输出电压。
总之，LM2596升压电路的原理是通过控制开关管的导通和关断，将输入电压转换成稳定的输出电压。
在实际应用中，需要根据具体电路参数和要求进行适当的调整和优化，以确保电路的正常工作和性能。
LM2596S-3.3-3A降压电压稳压器应用方案
随着科学技术的发展进步，电子元器逐渐智能化，多样化，应用的范围也越来越广泛。
LM2596系列:3A电流输出降压开关型集成稳压芯片，它内含固定频率振荡器（150KHZ），和基准稳压器（1.23v），并具有完善的保护电路：电流限制、热关断电路等。
利用该器件只需极少的外围器件便可构成高效稳压电路。
提供有：3.3V、5V、12V及可调（-ADJ）等多个电压档次产品。
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CAN收发器:NXP恩智浦CAN收发器 Microchip微芯CAN收发器十.分销产品线:ONSEMI安森美 TI德州仪器 ADI TOSHIBA东芝 AVAGO安华高十一 MCU单片机ABOV现代单片机MC96F系列 Microchip微芯单片机PIC12F PIC16F PIC18F系列FUJITSU富仕通单片机MB95F系列 STM单片机STM32F STM32L系列 CKS中科芯单片机CKS32F系列 TI单片机MSP430系列 TMS320F系列 NXP单片机LPC系列LM2596SNVS124C – NOVEMBER 1999 – REVISED APRIL 2013LM2596 SIMPLE SWITCHER ® Power Converter 150 kHz3A Step-Down Voltage RegulatorCheck for Samples: LM2596FEATURESDESCRIPTION• 3.3V, 5V, 12V, and Adjustable Output Versions • Adjustable Version Output Voltage Range,1.2V to 37V ±4% Max Over Line and Load The LM2596 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving a 3A load with excellent line and loadConditionsregulation. These devices are available in fixed output • Available in TO-220 and TO-263 Packages • Ensured 3A Output Load Current • Input Voltage Range Up to 40V• Requires Only 4 External Components voltages of 3.3V, 5V, 12V, and an adjustable output version.Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation , and a • Excellent Line and Load Regulationfixed-frequency oscillator.Specifications• 150 kHz Fixed Frequency Internal Oscillator The LM2596 series operates at a switching frequency of 150 kHz thus allowing smaller sized filter • TTL Shutdown Capabilitycomponents than what would be needed with lower • Low Power Standby Mode, I Q Typically 80 μA • High Efficiencyfrequency switching regulators. Available in a standard 5-lead TO-220 package with several different lead bend options, and a 5-lead TO-263 • Uses Readily Available Standard Inductors surface mount package.• Thermal Shutdown and Current Limit A standard series of inductors are available from Protectionseveral different manufacturers optimized for use with the LM2596 series. This feature greatly simplifies the APPLICATIONSdesign of switch-mode power supplies.• Simple High-Efficiency Step-Down (Buck)Other features include a ensured ±4% tolerance on Regulatoroutput voltage under specified input voltage and • On-Card Switching Regulators • Positive to Negative ConverterTypical Application(Fixed Output Voltage Versions)output load conditions, and ±15% on the oscillator frequency. External shutdown is included, featuring typically 80 μA standby current. Self protection features include a two stage frequency reducing current limit for the output switch and an over temperature shutdown for complete protection under fault conditions. (1)(1) † Patent Number 5,382,918.Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.SIMPLE SWITCHER is a registered trademark of Texas Instruments. All other trademarks are the property of their respective owners.PRODUCTION DATA information is current as of publication date. Copyright © 1999–2013, Texas Instruments IncorporatedProducts conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does notnecessarily include testing of all parameters.Connection DiagramsFigure 1. 5-Lead Bent and Staggered Leads, Figure 2. 5-Lead DDPAK/TO-263 (S) Package Through Hole TO-220 (T) Package See Package Number KTT0005BSee Package Number NDH0005DThese devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.(1)(2)(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions forwhich the device is intended to be functional, but do not ensure specific performance limits. For ensured specifications and test conditions, see the Electrical Characteristics.(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability andspecifications.(3) The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.Specifications with standard type face are for T J = 25°C, and those with boldface type apply over full Operating(1) Typical numbers are at 25°C and represent the most likely norm.(2) All limits specified at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limitsare 100% production tested. All limits at temperature extremes are ensured via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affectswitching regulator system performance. When the LM2596 is used as shown in the Figure 20 test circuit, system performance will be as shown in system parameters of Electrical Characteristics section.LM2596-5.0 Electrical CharacteristicsSpecifications with standard type face are for T J = 25°C, and those with boldface type apply over full Operating(1) Typical numbers are at 25°C and represent the most likely norm.(2) All limits specified at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limitsare 100% production tested. All limits at temperature extremes are ensured via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affectswitching regulator system performance. When the LM2596 is used as shown in the Figure 20 test circuit, system performance will be as shown in system parameters of Electrical Characteristics section.LM2596-12 Electrical CharacteristicsSpecifications with standard type face are for T J = 25°C, and those with boldface type apply over full Operating(1) Typical numbers are at 25°C and represent the most likely norm.(2) All limits specified at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limitsare 100% production tested. All limits at temperature extremes are ensured via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affectswitching regulator system performance. When the LM2596 is used as shown in the Figure 20 test circuit, system performance will be as shown in system parameters of Electrical Characteristics section.Specifications with standard type face are for T J = 25°C, and those with boldface type apply over full Operating(1) Typical numbers are at 25°C and represent the most likely norm.(2) All limits specified at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limitsare 100% production tested. All limits at temperature extremes are ensured via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affectswitching regulator system performance. When the LM2596 is used as shown in the Figure 20 test circuit, system performance will be as shown in system parameters of Electrical Characteristics section.All Output Voltage Versions Electrical CharacteristicsSpecifications with standard type face are for T J = 25°C, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, V IN = 12V for the 3.3V, 5V, and Adjustable version and V IN = 24V for the(1) Typical numbers are at 25°C and represent the most likely norm.(2) All limits specified at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limitsare 100% production tested. All limits at temperature extremes are ensured via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).(3) The switching frequency is reduced when the second stage current limit is activated.(4) No diode, inductor or capacitor connected to output pin.(5) Feedback pin removed from output and connected to 0V to force the output transistor switch ON.(6) Feedback pin removed from output and connected to 12V for the 3.3V, 5V, and the ADJ. version, and 15V for the 12V version, to forcethe output transistor switch OFF.(7) V IN = 40V.All Output Voltage Versions Electrical Characteristics (continued)Specifications with standard type face are for T J = 25°C, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, V IN = 12V for the 3.3V, 5V, and Adjustable version and V IN = 24V for the(8) Junction to ambient thermal resistance (no external heat sink) for the TO-220 package mounted vertically, with the leads soldered to aprinted circuit board with (1 oz.) copper area of approximately 1 in2.(9) Junction to ambient thermal resistance with the TO-263 package tab soldered to a single printed circuit board with 0.5 in2 of (1 oz.)copper area.(10) Junction to ambient thermal resistance with the TO-263 package tab soldered to a single sided printed circuit board with 2.5 in2 of (1oz.) copper area.(11) Junction to ambient thermal resistance with the TO-263 package tab soldered to a double sided printed circuit board with 3 in2 of (1 oz.)copper area on the LM2596S side of the board, and approximately 16 in2 of copper on the other side of the p-c board. See Application Information in this data sheet and the thermal model in Switchers Made Simple™ version 4.3 software.Typical Performance Characteristics(Circuit of Figure 20)NormalizedOutput Voltage Line RegulationFigure 3. Figure 4.Switch Saturation Efficiency VoltageFigure 5. Figure 6.Switch Current Limit Dropout VoltageFigure 7. Figure 8.(Circuit of Figure 20)Operating ShutdownQuiescent Current Quiescent CurrentFigure 9. Figure 10.Minimum Operating ON /OFF ThresholdSupply Voltage VoltageFigure 11. Figure 12.ON /OFF PinCurrent (Sinking) Switching FrequencyFigure 13. Figure 14.(Circuit of Figure 20)Continuous Mode Switching WaveformsFeedback Pin V IN = 20V, V OUT = 5V, I LOAD = 2ABias CurrentL = 32 μH, C OUT = 220 μF, C OUT ESR = 50 mΩA: Output Pin Voltage, 10V/div. B: Inductor Current 1A/div.C: Output Ripple Voltage, 50 mV/div.Figure 15.Figure 16. Horizontal Time Base: 2 μs/div.Discontinuous Mode Switching WaveformsLoad Transient Response for Continuous Mode V IN = 20V, V OUT = 5V, I LOAD = 500 mAV IN = 20V, V OUT = 5V, I LOAD = 500 mA to 2A L = 10 μH, C OUT = 330 μF, C OUT ESR = 45 mΩL = 32 μH, C OUT = 220 μF, C OUT ESR = 50 mΩA: Output Pin Voltage, 10V/div. B: Inductor Current 0.5A/div.C: Output Ripple Voltage, 100 mV/div.A: Output Voltage, 100 mV/div. (AC) B: 500 mA to 2A Load PulseFigure 17. Horizontal Time Base: 2 μs/div.Figure 18. Horizontal Time Base: 100 μs/div.Load Transient Response for Discontinuous ModeV IN = 20V, V OUT = 5V, I LOAD = 500 mA to 2A L = 10 μH, C OUT = 330 μF, C OUT ESR = 45 mΩA: Output Voltage, 100 mV/div. (AC) B: 500 mA to 2A Load PulseFigure 19. Horizontal Time Base: 200 μs/div.Test Circuit and Layout GuidelinesFixed Output Voltage VersionsC IN —470 μF, 50V, Aluminum Electrolytic Nichicon “PL Series” C OUT —220 μF, 25V Aluminum Electrolytic, Nichicon “PL Series” D1 —5A, 40V Schottky Rectifier, 1N5825 L1 —68 μH, L38where V REF = 1.23VAdjustable Output Voltage VersionsSelect R 1 to be approximately 1 kΩ, use a 1% resistor for best stability. C IN —470 μF, 50V, Aluminum Electrolytic Nichicon “PL Series” C OUT —220 μF, 35V Aluminum Electrolytic, Nichicon “PL Series” D1 —5A, 40V Schottky Rectifier, 1N5825 L1 —68 μH, L38 R1 —1 kΩ, 1%C FF —See Application Information SectionFigure 20. Standard Test Circuits and Layout GuidesAs in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance can generate voltage transients which can cause problems. For minimal inductance and ground loops, the wires indicated by heavy lines should be wide printed circuit traces and should be kept as short as possible. For best results, external components should be located as close to the switcher lC as possible using ground plane construction or single point grounding.If open core inductors are used, special care must be taken as to the location and positioning of this type of inductor. Allowing the inductor flux to intersect sensitive feedback, lC groundpath and C OUT wiring can cause problems.When using the adjustable version, special care must be taken as to the location of the feedback resistors and the associated wiring. Physically locate both resistors near the IC, and route the wiring away from the inductor, especially an open core type of inductor. (See Application Information section for moreinformation.)LM2596 Series Buck Regulator Design Procedure (Fixed Output)Table 1. LM2596 Fixed Voltage Quick Design Component Selection TableTable 1. LM2596 Fixed Voltage Quick Design Component Selection Table (continued)LM2596 Series Buck Regulator Design Procedure (Adjustable Output)= 1k (16.26 − 1) = 15.26k, closest 1% value is 15.4 kΩ. = 15.4 kΩ. Select a value for R 1 between 240Ω and 1.5 kΩ. The lower resistor values minimize noise pickup in the sensitive feedback pin. (For the temperature coefficient and the best stability 1% metal film resistors.)(2)2. Inductor Selection (L1)A. Calculate the inductor Volt • microsecond constant E • T (V • μs), from the following formula:where•V SAT = internal switch saturation voltage =1.16V•V D = diode forward voltage drop = 0.5V (4) B. Use the E • T value from the previous formula and match it with the E • T number on the vertical axis of the Inductor Value Selection Guide shown in Figure 24.C. on the horizontal axis, select the maximum load current.D. Identify the inductance region intersected by the E • T value and the Maximum Load Current value. Each region is identified by an inductance value and an inductor code (LXX).E. Select an appropriate inductor from the four manufacturer's part numbers listed in Table 3.E • T = 34.2 (V • μs)LOAD(max) = 3AFrom the inductor value selection guide shown ininductance region intersected by the 34 (V • μs) horizontalthe 3A vertical line is 47 μH, and the inductor code isFrom the table in Table 3, locate line L39, and select an inductor part number from the list of manufacturers part numbers.3. Output Capacitor SeIection (C OUT)See section on C OUT in Application Information section.From the quick design table shown in Table 2, locatevoltage column. From that column, locate the output voltage closest4. Feedforward Capacitor (C FF) (See Figure 20)For output voltages greater than approximately 10V, an additional capacitor is required. The compensation capacitor is typically between 100 pF and 33 nF, and is wired in parallel with the output voltage setting resistor, R2. It provides additional stability for high output voltages, low input-output voltages, and/or very low ESR output capacitors, such as solid tantalum capacitors.(6) This capacitor type can be ceramic, plastic, silver mica, etc. (Because of the unstable characteristics of ceramic capacitors made with Z5U material, they are not recommended.)LM2596 Series Buck Regulator Design Procedure (Adjustable Output)Table 2. Output Capacitor and Feedforward Capacitor Selection TableTable 2. Output Capacitor and Feedforward Capacitor Selection Table (continued)LM2596 Series Buck Regulator Design ProcedureINDUCTOR VALUE SELECTION GUIDES(For Continuous Mode Operation)Figure 21. LM2596-3.3 Figure 22. LM2596-5.0Figure 23. LM2596-12 Figure 24. LM2596-ADJTable 3. Inductor Manufacturers Part NumbersTable 4. Inductor Manufacturers Phone NumbersTable 5. Capacitor Manufacturers Phone NumbersTable 5. Capacitor Manufacturers Phone Numbers (continued)Table 6. Diode Selection TableBlock DiagramAPPLICATION INFORMATIONTable 7. PIN DESCRIPTIONSEXTERNAL COMPONENTSINPUT CAPACITORC IN—A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground pin. It must be located near the regulator using short leads. This capacitor prevents large voltage transients from appearing at the input, and provides the instantaneous current needed each time the switch turns on.The important parameters for the Input capacitor are the voltage rating and the RMS current rating. Because of the relatively high RMS currents flowing in a buck regulator's input capacitor, this capacitor should be chosen for its RMS current rating rather than its capacitance or voltage ratings, although the capacitance value and voltage rating are directly related to the RMS current rating.The RMS current rating of a capacitor could be viewed as a capacitor's power rating. The RMS current flowing through the capacitors internal ESR produces power which causes the internal temperature of the capacitor to rise. The RMS current rating of a capacitor is determined by the amount of current required to raise the internal temperature approximately 10°C above an ambient temperature of 105°C. The ability of the capacitor to dissipate this heat to the surrounding air will determine the amount of current the capacitor can safely sustain. Capacitors that are physically large and have a large surface area will typically have higher RMS current ratings. For a given capacitor value, a higher voltage electrolytic capacitor will be physically larger than a lower voltage capacitor, and thus be able to dissipate more heat to the surrounding air, and therefore will have a higher RMS current rating. The consequences of operating an electrolytic capacitor above the RMS current rating is a shortened operating life. The higher temperature speeds up the evaporation of the capacitor's electrolyte, resulting in eventual failure. Selecting an input capacitor requires consulting the manufacturers data sheet for maximum allowable RMS ripple current. For a maximum ambient temperature of 40°C, a general guideline would be to select a capacitor with a ripple current rating of approximately 50% of the DC load current. For ambient temperatures up to 70°C, a current rating of 75% of the DC load current would be a good choice for a conservative design. The capacitor voltage rating must be at least 1.25 times greater than the maximum input voltage, and often a much higher voltage capacitor is needed to satisfy the RMS current requirements.A graph shown in Figure 25 shows the relationship between an electrolytic capacitor value, its voltage rating, and the RMS c urrent it is rated for. These curves were obtained from the Nichicon “PL” series of low ESR, high reliability electrolytic capacitors designed for switching regulator applications. Other capacitor manufacturers offer similar types of capacitors, but always check the capacitor data sheet.“Standard” electrolytic capacitors typically have much higher ESR numbers, lower RMS current ratings and typically have a shorter operating lifetime.Because of their small size and excellent performance, surface mount solid tantalum capacitors are often used for input bypassing, but several precautions must be observed. A small percentage of solid tantalum capacitors can short if the inrush current rating is exceeded. This can happen at turn on when the input voltage is suddenly applied, and of course, higher input voltages produce higher inrush currents. Several capacitor manufacturers do a 100% surge current testing on their products to minimize this potential problem. If high turn on currents are expected, it may be necessary to limit this current by adding either some resistance or inductance before the tantalum capacitor, or select a higher voltage capacitor. As with aluminum electrolytic capacitors, the RMS ripple current rating must be sized to the load current.FEEDFORWARD CAPACITOR(Adjustable Output Voltage Version)C FF— A Feedforward Capacitor C FF, shown across R2 in Figure 20 is used when the ouput voltage is greater than 10V or when C OUT has a very low ESR. This capacitor adds lead compensation to the feedback loop and increases the phase margin for better loop stability. For C FF selection, see the Design Procedure section.Figure 25. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical)OUTPUT CAPACITORC OUT— An output capacitor is required to filter the output and provide regulator loop stability. Low impedance or low ESR Electrolytic or solid tantalum capacitors designed for switching regulator applications must be used. When selecting an output capacitor, the important capacitor parameters are; the 100 kHz Equivalent Series Resistance (ESR), the RMS ripple current rating, voltage rating, and capacitance value. For the output capacitor, the ESR value is the most important parameter.The output capacitor requires an ESR value that has an upper and lower limit. For low output ripple voltage, a low ESR value is needed. This value is determined by the maximum allowable output ripple voltage, typically 1% to 2% of the output voltage. But if the selected capacitor's ESR is extremely low, there is a possibility of an unstable feedback loop, resulting in an oscillation at the output. Using the capacitors listed in the tables, or similar types, will provide design solutions under all conditions.If very low output ripple voltage (less than 15 mV) is required, refer to the section on OUTPUT VOLTAGE RIPPLE AND TRANSIENTS for a post ripple filter.An aluminum electrolytic capacitor's ESR value is related to the capacitance value and its voltage rating. In most cases, higher voltage electrolytic capacitors have lower ESR values (see Figure 26 ). Often, capacitors with much higher voltage ratings may be needed to provide the low ESR values required for low output ripple voltage. The output capacitor for many different switcher designs often can be satisfied with only three or four different capacitor values and several different voltage ratings. See the quick design component selection tables in Table 1 and 4 for typical capacitor values, voltage ratings, and manufacturers capacitor types.Electrolytic ca pacitors are not recommended for temperatures below −25°C. The ESR rises dramatically at cold temperatures and typically rises 3X @ −25°C and as much as 10X at −40°C. See curve shown in Figure 27.Solid tantalum capacitors have a much better ESR spec for cold temperatures and are recommended for temperatures below −25°C.Figure 26. Capacitor ESR vs Capacitor Voltage Rating (Typical Low ESR Electrolytic Capacitor)CATCH DIODEBuck regulators require a diode to provide a return path for the inductor current when the switch turns off. This must be a fast diode and must be located close to the LM2596 using short leads and short printed circuit traces. Because of their very fast switching speed and low forward voltage drop, Schottky diodes provide the best performance, especially in low output voltage applications (5V and lower). Ultra-fast recovery, or High-Efficiency rectifiers are also a good choice, but some types with an abrupt turnoff characteristic may cause instability or EMI problems. Ultra-fast recovery diodes typically have reverse recovery times of 50 ns or less. Rectifiers such as the 1N5400 series are much too slow and should not be used.Figure 27. Capacitor ESR Change vs TemperatureINDUCTOR SELECTIONAll switching regulators have two basic modes of operation; continuous and discontinuous. The difference between the two types relates to the inductor current, whether it is flowing continuously, or if it drops to zero for a period of time in the normal switching cycle. Each mode has distinctively different operating characteristics, which can affect the regulators performance and requirements. Most switcher designs will operate in the discontinuous mode when the load current is low.The LM2596 (or any of the Simple Switcher family) can be used for both continuous or discontinuous modes of operation.In many cases the preferred mode of operation is the continuous mode. It offers greater output power, lower peak switch, inductor and diode currents, and can have lower output ripple voltage. But it does require larger inductor values to keep the inductor current flowing continuously, especially at low output load currents and/or high input voltages.To simplify the inductor selection process, an inductor selection guide (nomograph) was designed (see Figure 21 through 8). This guide assumes that the regulator is operating in the continuous mode, and selects an inductor that will allow a peak-to-peak inductor ripple current to be a certain percentage of the maximum design load current. This peak-to-peak inductor ripple current percentage is not fixed, but is allowed to change as different design load currents are selected. (See Figure 28.)Figure 28. (ΔI IND) Peak-to-Peak InductorRipple Current (as a Percentage of the Load Current)vs Load CurrentBy allowing the percentage of inductor ripple current to increase for low load currents, the inductor value and size can be kept relatively low.When operating in the continuous mode, the inductor current waveform ranges from a triangular to a sawtooth type of waveform (depending on the input voltage), with the average value of this current waveform equal to the DC output load current.Inductors are available in different styles such as pot core, toroid, E-core, bobbin core, etc., as well as different core materials, such as ferrites and powdered iron. The least expensive, the bobbin, rod or stick core, consists of wire wound on a ferrite bobbin. This type of construction makes for an inexpensive inductor, but since the magnetic flux is not completely contained within the core, it generates more Electro-Magnetic Interference (EMl). This magnetic flux can induce voltages into nearby printed circuit traces, thus causing problems with both the switching regulator operation and nearby sensitive circuitry, and can give incorrect scope readings because of induced voltages in the scope probe. Also see section on OPEN CORE INDUCTORS.When multiple switching regulators are located on the same PC board, open core magnetics can cause interference between two or more of the regulator circuits, especially at high currents. A torroid or E-core inductor (closed magnetic structure) should be used in these situations.The inductors listed in the selection chart include ferrite E-core construction for Schott, ferrite bobbin core for Renco and Coilcraft, and powdered iron toroid for Pulse Engineering.Exceeding an inductor's maximum current rating may cause the inductor to overheat because of the copper wire losses, or the core may saturate. If the inductor begins to saturate, the inductance decreases rapidly and the inductor begins to look mainly resistive (the DC resistance of the winding). This can cause the switch current to rise very rapidly and force the switch into a cycle-by-cycle current limit, thus reducing the DC output load current. This can also result in overheating of the inductor and/or the LM2596. Different inductor types have different saturation characteristics, and this should be kept in mind when selecting an inductor.The inductor manufacturer's data sheets include current and energy limits to avoid inductor saturation.。