基于ISL8088的高效2.25MHz降壓電源設計方案

Intersil 公司的ISL8088是雙路800mA低靜態電流高效2.25MHz同步降壓電源穩壓器，電源電壓從2.75V到5.5V，工作頻率2.25MHz，可使用小型低成本電感和電容，每路輸出電壓可低至0.6V，主要應用在DC/DC POL模塊，μC/μP, FPGA和DSP電源，路由器和交換機的插入DC/DC模塊，測試和測量系統，鋰離子電池和條形碼閱讀器。本文介紹ISL8088主要特性，方框圖，應用電路，以及ISL8088 EVAL1Z評估板主要特性，電路圖和所用材料清單。

Dual 800mA Low Quiescent Current 2.25MHz High Efficiency Synchronous Buck Regulator

The ISL8088 is a high efficiency, dual synchronous step-down DC/DC regulator that can deliver up to 800mA continuous output current per channel. The supply voltage range of 2.75V to 5.5V allows the use of a single Li+ cell, three NiMH cells or a regulated 5V input. The current mode control architecture enables very low duty cycle operation at high frequency with fast transient response and excellent loop stability. The ISL8088 operates at 2.25MHz switching frequency allowing the use of small, low cost inductors and capacitors. Each channel is optimized for generating an output voltage as low as 0.6V.

The ISL8088 has a user configurable mode of operation-forced PWM mode and PFM/PWM mode. The forced PWM mode operation reduces noise and RF interference while the PFM mode operation provides high efficiency by reducing switching losses at light loads. In PFM mode of operation, both channels draw a total quiescent current of only 30μA hence enabling high light load efficiency in order to maximize battery life.

The ISL8088 offers a 1ms Power-Good (PG) to monitor both output at power-up. When shutdown, ISL8088 discharges the outputs capacitor. Other features include internal digital soft-start, enable for power sequence, overcurrent protection, and thermal shutdown. The ISL8088 is offered in a 3mmx3mm 10 Ld DFN package with 1mm maximum height. The complete converter occupies less than 1.8cm2 area.

ISL8088主要特性：

? Internal Current Mode Compensation

? 100% Maximum Duty Cycle for Lowest Dropout

? Selectable Forced PWM Mode and PFM Mode

? External Synchronization up to 4MHz

? Start-up with Pre-biased Output

? Soft-Stop Output Discharge During Disabled

? Internal Digital Soft-Start - 2ms

? Power-Good (PG) Output with 1ms Delay

ISL8088應用：

? DC/DC POL Modules

? μC/μP, FPGA and DSP Power

? Plug-in DC/DC Modules for Routers and Switchers

? Test and Measurement Systems

? Li-ion Battery Power Devices

? Bar Code Readers

圖1。ISL8088方框圖

圖2。ISL8088典型應用電路圖

ISL8088 EVAL1Z評估板

The ISL8088 EVAL1Z kit is intended for use by individuals with requirements for Point-of-Load applications sourcing from 2.75V to 5.5V. The ISL8088EVAL1Z evaluation board is used to demonstrate the performance of the ISL8088 low quiescent current mode converter.

The ISL8088 is offered in a 3mmx3mm 10 Ld DFN package with 1mm maximum height. The complete converter occupies less than 1.8cm2 area.

ISL8088 EVAL1Z評估板主要特性：

? Dual 800mA High Efficiency Synchronous Buck Regulator with up to 97% Efficiency

? 800mA Guaranteed Output Current per channel

? Power-Goods (PG) output with 1ms Delay

? 2.75V to 5.5V Supply Voltage

? 3% Output Accuracy Over-Temperature/Load/Line

? Start up with Pre-biased Output

? Internal Digital Soft-Start - 2ms

? Soft-Stop Output Discharge During Disabled

? 30μA Quiescent Supply Current in PFM Mode

? Selectable Forced PWM Mode and PFM Mode

? External Synchronization up to 4MHz

? Typical 6.5μA Logic Controlled Shutdown Current

? 100% Maximum Duty Cycle for Lowest Dropout

? Internal Current Mode Compensation

? Peak Current Limiting.

? Over-Temperature Protection

? Independent Enable

圖3。ISL8088 EVAL1Z評估板電路圖

ISL8088 EVAL1Z評估板材料清單：