今天的便携式消费电子设备和行为几年前相比，你会明白为什么照明已成为主要的电源管理挑战。随着一个被动的LCD面板的手持设备正在迅速被淘汰。今天的设备具有高性能，高分辨率，2.5?3英寸彩色显示屏，支持从互联网接入和移动电视的视频回放的整个范围的应用范围。

典型，这些显示4个或更多所需的背光和LED驱动器。许多人（尤其是翻盖设计）手持设备增加了一个较小的副显示屏显示时间，日期和连接等基本信息。这些副主显示器屏幕通常需要超过1-2的LED背光。

作为产品差异化设计照明当今许多便携式电子设备的重要作用，工程师发现时尚需要额外的电源电路来驱动辅助RGB背光和键盘状态灯。

内置的电源电路设计更复杂的照相功能。一般是通过高的和少数LED驱动器在很短的时间电流闪光提供这些功能。但是，当手机制造商开始作此功能的初步介绍，他们是不足100万像素的CCD，这需要闪光驱动电流不超过100mA使用。今天的手持设备正被纳入设计工程师高得多的分辨率的CCD，如防治荒漠化公约要求高达600mA的电流仅用来驱动闪光功能，并提供足够的光来获取高分辨率的照片。电影模式和闪光灯功能，如相对为低功耗的需要而新的LED的时间更长，司机，而电源电路的设计难度增加。

因素考虑到这些事态发展，很容易理解为什么照明通常是最手持设备电池电源。前，通过提高设计工程师使用转换器，或在单独的电荷泵依靠向他们提供实现照明功能。不过，在照明功能和改善电力需求的增加，设计工程师需要更好地控制光照强度处理，管理，色彩平衡和{zd0}化的权力。这些工程师最终转向通过脉冲宽度调制（PWM）的系统微控制器，或者一个专门的控制器使用，控制来解决这些问题。

更简单的设计
近年来
，电源管理IC（PMIC）制造商已经开发各种工程师的目的是提供更高层次的控制和简化的IC设计。以美国国家半导体（NS）的氏LM27965例如，白光LED（白光LED）驱动器可以驱动多达9个并联LED，总输出高达180mA的电流。为了{zd0}限度地控制设计能力的工程师，可输出电流分别为2-3对照组，并配置4-5提供基于LED背光显示屏;为副显示屏幕提供背光2-3 LED配置;配置一个驱动器的管理国家或独立控制的LED指示器。每个LED通过标准I2C控制接口。

传感器虽然在许多应用解决方案的升压转换器仍然显示的优势。然而，在许多情况下，制造商开始转向混合模式电荷泵驱动或小型便携式应用分数的WLED，并且不再需要大量的传感器。虽然固定升压中的电荷输出泵是用来调节一个单独的电阻器，但LED电流匹配和效率可能受到影响。此外，混合模式电荷泵使用，输出电压可调制，以维持每个LED的恒定电流，使设计工程师更准确地匹配电流源。
许多类似的竞争性产品
是凌特公司（凌特）公司8月公布的LTC3219采用多模电荷泵，该设备可以在一个传导时间模式，然后当任何使能的LED电流源接近压降自动切换到升压模式，或1.5倍。

设备的电压下降后改用双（2x）模式。副为了支持主显示屏和RGB照明的要求，设备驱动程序有九个独立配置的电流源。

和NS技术设备，如在每个线性电流源设备，通过两线I2C为灰色，亮度，闪光和分级调节数字控制的串行接口。早期

的WLED需要相对较高的正电压和电流，以达到预期的亮度。然而，最近的技术进步使生产商能在电流低于10mA的工作的白光LED。这些设备可以比以前低的正向电压。最近的技术发展允许制造商开始提供PMIC的线性独立的电流源匹配，因为大多数外部设备不再需要降低成本，减少面积。

再如，TI的TPS75105提供了一个四通道LDO稳压器，并在一个极其紧凑的1.2 × 1.2mm的包了两辆坦克重视多达四个LED之间的匹配LED恒流驱动器。该产品不再需要感应升压转换器所需的传感器，输出电容和/或反馈电阻，或者采用混合模式电荷泵必须实现稳定开关电容和输入/输出电容。

相机闪光灯驱动器是一个更困难的挑战。设计工程师必须在规定时间内提供适量的光，并且不超过系统的权力，限制或限制LED的热量。由于基本开/关控制是不够的，许多设计工程师转向使用闪存，同时在子系统和相机快门系统微控制器的协调运行的算法。最近推出的智能LED闪光灯控制器品种xxx的发光控制。例如，今年早些时候，恩智浦半导体（NXP Semiconductors）该公司发布了UBA3001，该器件的LED闪光灯驱动器是{dy}个系列的器件，可支持整个电压范围高达90％的效率为一个高亮度发光二极管，提供高达1A的电流，支持高分辨率的照相手机。新IC还提供了闪光灯和摄像模式/视频模式的当前设置的xx控制权。

节省空间

当然，PCB的占用空间受限的便携式应用一直是非常宝贵的。

5月，Micrel公司日前针对嵌入式相机升压转换器的基础上，公布闪存驱动器MIC2298，该设备有200多万像素的分辨率，可以提供两个系列LED电流为1A。该器件可在3?3mm的MLF封装，只需要一个传感器2uH结构紧凑，小型的陶瓷电容器。

其他制造商是通过把照明设备的功能，以帮助设计工程师节省电路板空间，同时降低元件数量，面积和更低的成本更广泛。为手机的LCD和相机模块空间嵌入式上半年受限的直，折叠手机或滑盖手机，美国信（马克西姆）最近发布了WLED驱动器系列，在4 × 4mm的微型系列-包添加移动电话两个相机模块用于驱动可编程200mA LDO稳压器。{zd0}8645X和8645Y分数收取的{zg}30mA的电流用于驱动多达6个WLED的水泵，并有5个调光器的准确性。这些器件也可以在{zg}200mA的电流驱动两个WLED的，照相机闪光灯应用。

同样，研诺（AnalogicTech）是发出了一个电荷泵为AAT2846的基础上，该设备将有六个背光驱动器，2闪存驱动器和两个通用低压降稳压器与两个独立的单在一颗芯片上集成数字接口。这使得设计工程师建立一个提供背光和闪光解决方案独立控制，使他们对这些控制程序设置大量。 6背光输出可以合成为一个单一的大显示屏，分为5 +1配置屏幕划分为主要副或。

Lighting demand has become increasingly complicated and technical challenges encountered power chips!

To today’s portable consumer electronic devices and the conduct of a few years ago compared to, you will understand why the lighting has become a leading power management challenges. With a single passive LCD panel of the handheld devices is rapidly be eliminated. Today’s devices have a high-performance, high-resolution, 2.5 ~ 3-inch diagonal color display to support the range from Internet access and mobile television to the entire range of video playback applications.

typical, these display four or more required for the backlight and the LED drive. Many handheld devices (especially the clamshell design) are increased by a smaller Vice display to show time, date and connectivity and other basic information. These Vice-screen main display is usually required more than 1-2 for the LED backlight.

found in fashion as the design engineers in product differentiation lighting the important role of many of today’s portable electronic devices are required extra power circuit to drive the auxiliary RGB backlight and keyboard status lights.

built-in camera functions of a higher complexity of the power circuit design. These features generally through high current in a very short duration with a small number of LED drivers to provide the flash. But when the handset manufacturers start to make the initial introduction of this feature, they are used less than one million pixel CCD, which requires flash drive current does not exceed 100mA. Today’s handheld devices are being integrated design engineers much higher-resolution CCD, such CCD request up to 600mA of current is only used to drive flash function, and provide enough light to obtain high-resolution photos. Movie mode and flash functions, such as relatively new as a result of the need for low power LED driver for a longer duration, while the increase of power supply circuit design more difficult.

factors to take into account these developments, it is easy to understand why the lighting is usually the most handheld devices are battery power source of the. Ago, design engineers through the use of boost converter, or to rely on a separate charge pump to provide them realize the illumination function. However, with the increase in the number of lighting functions and power requirements improve, design engineers need to better control the light intensity treatment, management, color balance and maximize the power. These engineers eventually shift the system microcontroller, or the use of a dedicated controller, through pulse width modulation (PWM) control to solve these problems.

more simple design

in recent years, power management IC (PMIC) manufacturers have developed various Engineer aims to provide a higher level control and simplify the design of the IC. To the United States National Semiconductor (NS)’s LM27965 example, the white LED (WLED) driver can drive up to nine parallel LED, the total output up to 180mA. In order to maximize the ability to control design engineers can be output currents are divided into 2-3 separate control group, and configure 4-5 provides LED-based backlight display; 2-3 LED configuration for the Vice show screen to provide backlighting; configure a single independent control of the drive to manage the state or the indicator LED. Each LED through the standard I2C control interface.

Although sensors based on the boost converter solution for many applications still show the advantages. However, in many cases, manufacturers are beginning to shift to mixed-mode charge pump to drive or scores of compact portable applications WLED, and is no longer required large sensors. Although the fixed-step-up in the output of charge pump are used to modulate a separate resistor, but the LED current matching and efficiency may be affected. The use of mixed-mode charge pump, the output voltage can be modulated to maintain the constant current for each LED, making design engineers more accurately match the current source.

with many similar competitive products is that Linear Technology (LinearTechnology) company in August released LTC3219 using multi-mode charge pump, the device can be in one mode of conduction times, and then when any enabled LED current source close to voltage drop automatically switch to boost mode, or 1.5 times.

subsequent voltage drop of the device to switch to double (2x) mode. Vice in order to support the main display and RGB lighting requirements, the device driver has nine individually configurable current sources.

and NS devices, like Linear Technology devices in each current source through two-wire I2C serial interface for digital control of gray, brightness, flash and hierarchical regulation. WLED early

required relatively high positive voltage and current in order to achieve the desired luminosity. However, recent technological advances have allowed manufacturers be able to work in the current below 10mA the WLED. These devices can be lower than before the forward voltage. Recent technological developments have allowed manufacturers to start providing PMICs linear independent current source matching, because the majority of external devices are no longer required to reduce the cost and reduce the footprint area.

For another example, TI’s TPS75105 provides a four-channel LDO, and in an extremely compact 1.2 × 1.2mm package two tanks attached to up to four LED matching LED constant current drive. The product is no longer necessary sensors needed boost converter sensor, the output capacitor and / or feedback resistor, or to use mixed-mode charge pump required to realize the stability of switched-capacitor and the input / output capacitance.

camera flash drive is a more difficult challenge. Design Engineer must be in a specified time to provide the right amount of light, and does not exceed the system power to restrict or limit the LED’s heat. Due to the basic on / off control is not sufficient, many design engineers turn to the use of flash by at the same time the coordination of subsystems and camera shutter system microcontroller running algorithms. Recently introduced a variety of intelligent LED flash controller has a more efficient light-emitting control. For example, earlier this year, NXP Semiconductors (NXP) the company issued a UBA3001, the device LED flash drives are the first series of devices, can support the entire voltage range up to 90% efficiency level, for a single high-brightness LED delivers up to 1A of current to support with high-resolution camera phone. The new IC also provides for the flashlight mode and camera / video mode full control of current settings.

save space

course, PCB’s footprint for space-constrained portable applications has always been very precious.

May, Micrel Inc. has released for embedded cameras boost converter based on the flash drive MIC2298, the device has more than two million pixel resolution, can be provided for the two series LED current of 1A . The device is available in 3 ~ 3mm MLF package, only need one sensor 2uH compact and small ceramic capacitors.

other manufacturers is through a wider range of lighting functionality into devices to help design engineers to save board space while reducing the footprint quantity components and lower costs. For the first half of the phone’s LCD and camera modules embedded in space-constrained mobile phones straight, folding mobile phone or slider phone, the U.S. letter (Maxim) recently released a WLED driver family, the series of 4 × 4mm micro - package add two camera modules used to drive programmable 200mA LDO. Max 8645X and 8645Y Score charge pump used at the highest 30mA of current drive up to six WLED, and has five dimmers accuracy. These devices can also be at the highest current of 200mA drive two WLED, for camera flash applications.

Similarly, Advanced Analogic (AnalogicTech) has issued a charge pump based on the AAT2846, the device will be six backlight drivers, 2 flash drives and two general-purpose LDO with two independent single digital interface integration on a single IC. This allows design engineers to build a provide independent control of backlight and flash solutions and allow them a large number of settings of these control program. 6 backlight output can be synthesized for a single large display, or divided into 5 +1 configuration screen for the main vice. (07-11-30)