原标题：NS LMZ14203 3A DC-DC解决方案

　　NS 公司的LMZ1420x 和LMZ1200x SIMPLE SWITCHER 是容易使用的3A DC/DC解决方案,有极好的电源转换效率,输出电压精度,线路和负载调整, LMZ14203/2/1输入电压在6-42V之间, LMZ12003/2/1输入电压在4.5V-20V之间,输出电压可低至 0.8V,高至6V.效率高达90%.主要用在POL,空间受限和高热需求的应用,负输出电压应用.本文介绍LMZ1420x 和LMZ1200x主要特性, 应用方框图和LMZ1420x / LMZ1200x 评估板与材料清单(BOM).

　　The LMZ1420x and LMZ1200x SIMPLE SWITCHER? Power modules are easy-to-use DC-DC solution capable of driving up to a 3A load with exceptional power conversion efficiency, output voltage accuracy, line and load regulation. They are available in an innovative package that enhances thermal performance and allows for hand or machine soldering.

　　The LMZ14203/2/1 can accept an input voltage rail between 6V and 42V and the LMZ12003/2/1 can accept an input voltage rail between 4.5V and 20V. The devices can deliver an adjustable and highly accurate output voltage as low as 0.8V and as high as 6V. The control structure is constant on-time with input voltage feed forward. This creates a nearly constant switching frequency across the input voltage range. The control loop operates well with low ESR output capacitors such as ceramics. An output feed-forward capacitor across the upper feedback resistor trims for optimum transient response.

　　The precision enable input allows for programmable UVLO of the input supply. The external soft-start capacitor facilitates controlled startup output rise time. The LMZ1420x and LMZ1200x family is a reliable and robust solution with the following features: lossless cycle-by-cycle valley current limit to protect for over current or short-circuit fault, thermal shutdown, input under-voltage lock-out, and will start up into a prebiased output.

　　LMZ14203性能优势:

　　■ Operates at high ambient temperature with no thermal derating

　　■ High efficiency reduces system heat generation

　　■ Low radiated emissions (EMI) complies with EN55022 class B standard

　　■ Passes 10V/m radiated immunity EMI test standard EN61000 4-3

　　LMZ14203电指标:

　　■ 18W maximum total output power

　　■ Up to 3A output current

　　■ Input voltage range 6V to 42V

　　■ Output voltage range 0.8V to 6V

　　■ Efficiency up to 90%

　　LMZ14203主要特性:

　　■ Integrated shielded inductor

　　■ Simple PCB layout

　　■ Flexible startup sequencing using external soft-start and precision enable

　　■ Protection against inrush currents and faults such as input UVLO and output short circuit

　　■ – 40℃ to 125℃ junction temperature range

　　■ Single exposed pad and standard pinout for easy mounting and manufacturing

　　■ Fast transient response for powering FPGAs and ASICs

　　■ Low output voltage ripple

　　■ Pin-to-pin compatible family:

　　LMZ14203/2/1 (42V max 3A, 2A, 1A)

　　LMZ12003/2/1 (20V max 3A, 2A, 1A)

　　■ Fully enabled for Webench? Power Designer

　　LMZ14203应用:

　　■ Point of load conversions from 12V and 24V input rail

　　■ Time critical projects

　　■ Space constrained / high thermal requirement applications

　　■ Negative output voltage applications

　　图1.LMZ14203简化应用电路图

　　图2.LMZ14203应用方框图

　　LMZ1420x / LMZ1200x 评估板

　　评估板指标:

　　• LMZ1420x VIN = 6V to 42V

　　• LMZ1420x enable UVLO = 8V

　　• LMZ1420x VOUT = 3.3V

　　• LMZ1200x VIN = 4.5V to 20V

　　• LMZ1200x enable UVLO = 4.5V

　　• LMZ1200x VOUT = 1.8V

　　• Operates at full load up to 80℃ ambient at 12V input

　　• θJA = 20℃/ W, θJC = 1.9℃/W

　　• Designed on four layers, all four layers are 1 oz. copper weight

　　• The two internal ground planes are identical

　　• Measures 1.705 in. x 3.03 in. (4.33 cm x 7.7cm) and is 62mil (.062”) thick of FR4 laminate material

　　图3.LMZ1420x / LMZ1200x 评估板电路图

　　LMZ1420x / LMZ1200x 评估板材料清单(BOM):