LM5119設計的雙路DC-DC 20A電源控制方案

本文介紹了LM5119主要特性，方框圖，典型應用電路圖和LM5119EVAL評估板主要特性，電路圖和材料清單（BOM）。

NS 公司的LM5119是雙路同步電流模式降壓控制器，工作電壓從5.5V到65V，開關頻率從50kHz 到 750kHz，具有強固的3.3A峰值柵極驅動器，可編程輸出從0.8V起到輸入電壓的90%，輸出電流高達20A，主要用在需要精密電壓穩(wěn)壓器如通信，汽車電子以及工業(yè)控制應用。

LM5119主要特性：

■ Emulated peak current mode control

■ Wide operating range from 5.5V to 65V

■ Easily configurable for dual outputs or interleaved single output

■ Robust 3.3A peak gate drive

■ Switching frequency programmable to 750kHz

■ Optional diode emulation mode

■ Programmable output from 0.8V

■ Precision 1.5% voltage reference

■ Programmable current limit

■ Hiccup mode overload protection

■ Programmable soft-start

■ Programmable line under-voltage lockout

■ Automatic switch-over to external bias supply

■ Channel2 enable logic input

■ Thermal Shutdown

■ Leadless LLP32 (5mm x 5mm) package

圖1。LM5119方框圖

圖2。LM5119典型應用電路圖

圖3。LM5119 10V 4A和5V 8A典型應用電路圖

LM5119EVAL評估板

The LM5119EVAL evaluation board provides the design engineer with a fully functional dual output buck converter, employing the LM5119 Dual Emulated Current Mode Synchronous Buck Controller. The evaluation board is designed to provide both 10V and 5V outputs over an input range of 14V to 55V. Also the evaluation board can be easily configured for a single 10V, 8A regulator.

LM5119EVAL評估板主要特性：

Performance of the Evaluation Board

? Input Voltage Range: 14V to 55V

? Output Voltage: 10V (CH1), 5V (CH2)

? Output Current: 4A (CH1), 8A (CH2)

? Nominal Switching Frequency: 230 KHz

? Synchronous Buck Operation: Yes

? Diode Emulation Mode: Yes

? Hiccup Mode Overload Protection: Yes

? External VCC Sourcing: Yes

Powering and Loading Consideration

When applying power to the LM5119 evaluation board, certain precautions need to be followed. A misconnection can damage the assembly.

PROPER BOARD CONNECTION

The input connections are made to the J1 (VIN) and J2 (RTN/ GND) connectors. The CH1 load is connected to the J3 (OUT1+) and J4 (OUT1-/GND) and the CH2 load is connected to the J6 (OUT2+) and J5 (OUT2-/GND). Be sure to choose the correct connector and wire size when attaching the source power supply and the load.

SOURCE POWER

The power supply and cabling must present low impedance to the evaluation board. Insufficient cabling or a high impedance power supply will droop during power supply application with the evaluation board inrush current. If large enough, this droop will cause a chattering condition during power up. During power down, insufficient cabling or a high impedance power supply will overshoot. This overshoot will cause a non-monotonic decay on the output.

An additional external bulk input capacitor may be required unless the output voltage droop/overshoot of the source power is less than 0.7V. In this board design, UVLO setting is conservative while UVLO hysteresis setting is aggressive.

Minimum input voltage can goes down with an aggressive design. Minimum operating input voltage depends on the output voltage droop/overshoot of the source power supply and the forced off-time of the LM5119. Refer to the LM5119 datasheet for complete design information.

LOADING

When using an electronic load, it is strongly recommended to power up the evaluation board at light load and then slowly increase the load. If it is desired to power up the evaluation board at maximum load, resistor banks must be used. In general, electronic loads are best suited for monitoring steady state waveforms.

AIR FLOW

Prolonged operation with high input voltage at full power will cause the MOSFETs to overheat. A fan with a minimum of 200LFM should be always provided.

圖4。LM5119EVAL評估板連接圖

圖5。LM5119EVAL評估板電路圖

LM5119EVAL評估板材料清單（BOM）：