基于ISL8088的高效2.25MHz降压电源设计方案

Intersil 公司的ISL8088是双路800mA低静态电流高效2.25MHz同步降压电源稳压器，电源电压从2.75V到5.5V，工作频率2.25MHz，可使用小型低成本电感和电容，每路输出电压可低至0.6V，主要应用在DC/DC POL模块，μC/μP, FPGA和DSP电源，路由器和交换机的插入DC/DC模块，测试和测量系统，锂离子电池和条形码阅读器。本文介绍ISL8088主要特性，方框图，应用电路，以及ISL8088 EVAL1Z评估板主要特性，电路图和所用材料清单。

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应用：

• 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

图1。ISL8088方框图

图2。ISL8088典型应用电路图

ISL8088 EVAL1Z评估板

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评估板主要特性：

• 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

图3。ISL8088 EVAL1Z评估板电路图

ISL8088 EVAL1Z评估板材料清单：