基于LM27402設(shè)計的20A高性能同步降壓電源控制技術(shù)

The LM27402 is a synchronous voltage mode DC/DC buck controller with inductor DCR current sense capability. Sensing the inductor current eliminates the need to add resistive

powertrain elements which increases overall efficiency and facilitates accurate continuous current limit sensing. A 0.6V ±1% voltage reference enables high accuracy and low voltage capability at the output. An input operating voltage range of 3V to 20V makes the LM27402 suitable for a large variety of input rails.

The LM27402 voltage mode control loop incorporates input voltage feed-forward to maintain stability throughout the entire input voltage range. The switching frequency is adjustable from 200 kHz to 1.2 MHz. Dual high current integrated Nchannel MOSFET drivers support large QG, low RDS(ON) MOSFETs. A power good indicator provides power rail sequencing capability and output fault detection. Adjustable external soft-start capability limits inrush current and provides monotonic output control during startup. Other features include external tracking of other power supplies, integrated LDO bias supply, and synchronization capability. The LM27402 is offered in a 16 pin eTSSOP package and a 4 mm x 4 mm 16 pin exposed LLP.

LM27402主要特性：

■ Input operating voltage range of 3V to 20V

■Continuous inductor DCR or shunt resistor current sensing

■0.6V ±1% reference ( -40℃ to 125 ℃

junction temperature)

■ Output voltage as high as 95% of input voltage

■ Integrated MOSFET drivers

■ Internal LDO bias supply

■ External clock synchronization

■ Adjustable soft-start with external capacitor

■ Pre-biased startup capability

■ Power supply tracking

■ Input voltage feed-forward

■ Power good indicator

■ Precision enable with hysteresis

LM27402應(yīng)用：

■ High current, low voltage FPGA/ASIC DC/DC converters

■ General purpose high current buck converters

■ Telecom, datacom, networking, distributed power Architectures

圖1。LM27402方框圖

圖2。LM27402典型連接圖

圖3。LM27402應(yīng)用電路圖：5V-12V輸入，15V輸出，輸出電流20A，fsw= 300KHZ

所用元件列表：

圖4。LM27402應(yīng)用電路圖：5Ｖ－12Ｖ輸入，3．3Ｖ輸出，輸出電流25A，ｆｓｗ＝300 kHz
所用元件列表：

圖5。 LM27402應(yīng)用電路圖：3.3V輸入，0.9V輸出，輸出電流20A，fsw = 500 kHz
所用元件列表：

LM27402評估板
The LM27402 evaluation board represents a 20A typical application circuit. The application circuit is optimized for an input voltage of 12V. However, input voltage feed-forward technology allows the evaluation board to operate up to 20V while maintaining a stable output voltage of 1.5V at 20A.
Temperature compensated inductor DCR current limit circuitry provides a steady current limit setpoint. Extra MOSFET and input/output capacitor footprints are included to accommodate higher currents if desired. An externally set soft-start time of 10 ms provides a controlled monotonic startup. The LM27402 evaluation board also supports pre-biased startup and provides a tracking connection for power supply sequencing.

An external clock can be applied to change the switching frequency through an on board synchronization connection. PGOOD is externally pulled up to VDD and can be monitored via an on board terminal. Two extra terminals are included to provided a network analyzer connection for control loop stability analysis. The PCB measures 1.3” x 1.8” and includes input/output banana connectors for the input supply and load



圖6。LM27402評估板外形圖
Evaluation Board Operating Specifications
? Input Voltage = 4.5V to 20V
? Output Voltage = 1.5V
? Output Current = 0A to 20A



圖7。LM27402評估板電路圖：VIN = 4.5V- 20V, VOUT = 1.5V, IOUT = 20A
LM27402評估板材料清單（BOM）：