NS LM5118升降压开关稳压方案

NS公司的LM5118是宽电压范围的升/降压开关稳压器控制器,具有实现高性能高性价比升/降压稳压器所有功能,输入电压从3V到75V,开关频率可编程到500kHz.控制器包括用来驱动高边降压MOSFET和低边升压MOSFET的驱动器,降压模式和升压模式可平滑变换,特别适合于汽车电子应用.本文介绍了LM5118的主要特性, 方框图和应用电路图, 典型应用电路图以及12V 3A 典型应用电路图, 评估板电路图和评估板材料清单(BOM).

The LM5118 wide voltage range Buck-Boost switching regulator controller features all of the functions necessary to implement a high performance cost efficient Buck-Boost regulator using a minimum of external components. The Buck-Boost topology maintains output voltage regulation when the input voltage is either less than or greater than the output voltage making it especially suitable for automotive applications. The LM5118 operates as a buck regulator while the input voltage is sufficiently greater than the regulated output voltage and gradually transitions to the buck-boost mode as the input voltage approaches the output. This dual mode approach maintains regulation over a wide range of input voltages with optimal conversion efficiency in the buck mode and a glitch-free output during mode transitions. This easy to use controller includes drivers for the high side buck MOSFET and the low side boost MOSFET. The regulator’s control method is based upon current mode control utilizing an emulated current ramp. Emulated current mode control reduces noise sensitivity of the pulse-width modulation circuit, allowing reliable control of the very small duty cycles necessary in high input voltage applications. Additional protection features include current limit, thermal shutdown and an enable input. The device is available in a power enhanced TSSOP-20 package featuring an exposed die attach pad to aid thermal dissipation.

主要特性:
Ultra-wide input voltage range from 3V to 75V
Emulated peak current mode control
Smooth transition between step-down and step- up modes
Switching frequency programmable to 500KHz
Oscillator synchronization capability
Internal high voltage bias regulator
Integrated high and low-side gate drivers
Programmable soft-start time
Ultra low shutdown current
Enable input wide bandwidth error amplifier
1.5% feedback reference accuracy
Thermal shutdown



图1.LM5118方框图和应用电路图



图2.12V 3A 典型应用电路图



图3.LM5118典型应用电路图

LM5118评估板

The LM5118 evaluation board is designed to provide the design engineer with a fully functional, Emulated Current Mode Control, buck-boost power converter to evaluate the LM5118 controller IC. The evaluation board provides a 12V output with 3A of output current capability. The evaluation board’s wide input voltage range is from 75V to 5V, with operation down to 3V with some component changes. The evaluation board operates
at 300 kHz, a good compromise between conversion efficiency, tradeoffs between buck and buck-boost mode requirements, and converter size. The printed circuit board
consists of 4 layers with 2 ounce copper top and bottom, and 1 ounce copper on internal layers. The board is constructed with FR4 material. This application note contains the evaluation board schematic, Bill-of-Materials (BOM) and a quick setup procedure. Refer to the LM5118 data sheet and quick start for more complete circuit and design information.




图4.LM5118评估板电路图
LM5118评估板材料清单(BOM):