ADI ADP2121高性能6MHz小型电源方案

ADI公司的ADP2121是高频(6MHz)低静态电流降压DC/DC转换器, 非常适合手提设备的应用.固定频率6MHz使得可采用微型电容和电感,同步整流可提高效率,外接元件数量很少.峰值效率可高达92%,输入电压从2.3 V 到5.5 V, 固定输出电压1.80 V, 1.82 V, 1.85V和1.875V ,连续输出电流500A, 可用在手机,数码相机,数字音频,手提设备以及单节锂电池充电器等.本文介绍了ADP2121的主要特性,内部方框图,应用电路配置图,以及所用电感,输入和输出电容的数值选取.

The ADP2121 is a high frequency, low quiescent current, step-down, dc-to-dc converter optimized for portable applications in which board area and battery life are critical constraints. Fixed frequency operation at 6 MHz enables the use of tiny ceramic inductors and capacitors. Additionally the synchronous rectification improves efficiency and results in fewer external components. At high load currents, the device uses a voltage regulating pulse-width modulation (PWM) mode that maintains a constant frequency with excellent stability and transient response. At light load conditions, the ADP2121 can automatically enter a power saving mode that utilizes pulse-frequency modulation (PFM) to reduce the effective switching frequency and ensure the longest battery life in portable applications. During logic controlled shutdown (EN = 0), the input is disconnected from the output and draws less than 0.28 μA (typical) from the source.

The ADP2121 has an input voltage range of 2.3 V to 5.5 V allowing the use of a single Li+/Li-polymer cell, multiple alkaline/Ni-MH cell, PCMCIA, and other standard power sources. The converter is internally compensated to minimize external components, and its 1.80 V, 1.82 V, 1.85 V, or 1.875 V fixed output can source up to 500 mA. Other key features include undervoltage lockout (UVLO) to prevent deep-battery discharge and soft start to prevent input current overshoot at startup.

ADP2121主要特性:
92 % peak efficiency
6 MHz operating frequency
38 μA (typical) no load quiescent current in PFM mode
1.80 V, 1.82 V, 1.85V, 1.875V fixed output voltage
500 mA continuous output current
Input voltage :2.3 V to 5.5 V
0.28 μA (typical) shutdown supply current
Automatic power-saving mode
Compatible with tiny multilayer inductors
Internal synchronous rectifier
Internal compensation
Internal soft start
Output to ground short circuit protection
Current-limit protection
Enable/shutdown logic input
Undervoltage lockout
Thermal shutdown
Ultra small 6-ball 1.17 mm2 WLCSP

ADP2121应用:
Mobile phones
Digital cameras
Digital audio
Portable equipment
1 cell Li+/Li-polymer and 3-cell alkaline/nickel



图1.ADP2121内部方框图



图2.ADP2121电路配置图
推荐的电感选择表:



推荐的输入和输出电容选择表: