研诺逻辑AAT2688 4.5A PMIC方案

研诺逻辑(ANALOGIC TECHNOLOGIES )公司的AAT2688 是4.5A PMIC解决方案,具有两个高性能降压转换器:高压同步降压稳压器(输入电压6-24V,输出电压0.8V-5.5V可调,输出电流4.5A)和低输入电压降压低压差(LDO)稳压器(输入电压2.7V-5.5V,输出电流600mA,600mA时的压差为1V),适用于12V适配器系统如DSL和线缆调制解调器,笔记本电脑,卫星电视机顶盒和无线LAN系统.本文介绍了AAT2688的主要特性,方框图, 典型应用电路图和评估板电路图以及AAT2688 设计案例.

AAT2688:4.5A PMIC Solution for 12V Adapter Systems with 2-Output High Performance Step-Down Converters

The AAT2688 provides two independently regulated DC outputs: a high voltage synchronous step-down (Buck) regulator and a low input voltage step-down low dropout
(LDO) regulator. The PMIC is optimized for low cost 12V adapter inputs, making the device the ideal system-ona- chip power solution for consumer communications
equipment.

Channel 1 is a step-down regulator with an input voltage range of 6.0V to 24V, providing up to 4.5A output current. 490kHz fixed switching frequency allows small L/C filtering components. Channel 1 utilizes voltage mode control configured for optimum performance across the entire output voltage and load range.
Channel 2 is a low-dropout (LDO) regulator providing up to 600mA output current. The device provides low output noise, low quiescent current, and excellent transient response.

The step-down regulator includes integrated over-current, soft-start and over-temperature protection. Independent input and enable pins provide maximum design flexibility.

The AAT2688 is available in the Pb-free 4mm x 5mm 24-pin TQFN package. The rated operating temperature range is -40°C to 85°C.

AAT2688主要特性:
2-Output Step-Down Converters:
Channel 1 (Buck): VIN1 = 6.0 to 24.0V
VOUT1 Adjustable from 0.8V to 5.5V
IOUT1 up to 4.5A
High Switching Frequency
Voltage Mode Control
High Accuracy ±1.5%
PWM Fixed Frequency for Low Ripple
Channel 2 (LDO): VIN2 = 2.7V to 5.5V
IOUT2 up to 600mA
1V Dropout Voltage at 600mA IOUT
Small Solution Size
System on a Chip
Ultra-small External L/C
Shutdown Current <35μA
Independent Enable Pins
Over-Current and Over-Temperature Protection
Internal Soft Start
4x5mm 24-Pin TQFN Low Profile Package
-40°C to 85°C Temperature Range

主要应用:
DSL and Cable Modems
Notebook Computers
Satellite Set-top Boxes
Wireless LAN Systems



图1.AAT2688方框图



图2. AAT2688典型应用电路图



图3. AAT2688评估板电路图(VIN = 6V-24V和VOUT = 3.3V)

AAT2688 设计案例:
指标
VO1 = 3.3V @ 4.5A, Pulsed Load ΔILOAD = 4.5A
VO2 = 1.8V @ 600mA
VIN1 = 12V
FS = 490kHz
TAMB = 85°C in TQFN45-24 package
器件选择和计算公式: