ST L5987基于L5987高效直流3A电源DC－DC参考设计方案

ST公司的L5987是一款具有内嵌最小3.5A电流限制功率MOSFET场效应管的降压型开关稳压器件。输入电压范围为2.9V至18V，输出电压范围为0.6V至Vin。为减少外围器件及PCB尺寸，内嵌振荡器开关频率为250kHz，此振荡器可通过外部调节，使振荡器开关频率达到1MHz。本文首先介绍芯片的简介、特性及应用领域，并给出相应设计方案的设计原理图、元器件列表及PCB元件布局图。
The L5987 is a step-down switching regulator with 3.5 A (minimum) current limited embedded power MOSFET, so it is able to deliver up to 3 A current to the load depending on the application conditions.
The input voltage can range from 2.9 V to 18 V, while the output voltage can be set starting from 0.6 V to VIN. Having a minimum input voltage of 2.9 V, the device is suitable also for 3.3 V bus.
Requiring a minimum set of external components, the device includes an internal 250 kHz switching frequency oscillator that can be externally adjusted up to 1 MHz.
The QFN and the HSOP packages with exposed pad allow reducing the RthJA down to 60℃/W and 40℃/W respectively.
L5987主要特性：
■ 3 A DC output current
■ 2.9 V to 18 V input voltage
■ Output voltage adjustable from 0.6 V
■ 250 kHz switching frequency, programmable up to 1 MHz
■ Internal soft-start and inhibit
■ Low dropout operation: 100% duty cycle
■ Voltage feed-forward
■ Zero load current operation
■ Over current and thermal protection
■ VFQFPN3x3-8L and HSOP8 package
L5987应用：
■ Consumer:
STB, DVD, DVD recorder, car audio, LCD TV and monitors
■ Industrial:
PLD, PLA, FPGA, chargers
■ Networking:
XDSL, modems, DC-DC modules
■ Computer:
Optical storage, hard disk drive, printers, audio/graphic cards
■ LED driving
 
图1. L5987内部方框图
L5987方案介绍：
The EVAL5987/A demonstration board provides the design engineer with a fully functional stepdown switching regulator with an output current of up to 3 A. The board integrates STMicroelectronics’ L5987/A step-...