4

0HV

APPLICATION and PCB reference:

1. Put input capacitor close to

HM3123 and larger than 100uF or 200uF if over 60V input.

尽量把输入电容靠近芯片输入脚

,容量不小于100uF,如输入电压超过70V,最好在输入对GND加80V的TVS管,防止过冲.

2. Put Schottky diode close to SW and GND pin of chip , choose better heat-sink package like SMB or SMC.

尽量把肖特基二极管靠近芯片的

SW脚与GND，选择SMB或SMC等散热好的封装.电流耐压都要有20%以上的余量.

3. Choose high efficiency inductor, like the Iron-silicon-aluminum, or some SMT inductors.

尽量选择材质好点的贴片电感或铁硅铝电感

.标称电流相对实际电流要有50%的余量.

4. The external NMOS, choose the Vds value 20V higher than the input volage at least.

外置

MOS的标称耐压要比实际的输入电压高20V,譬如输入70V, 选择100V的MOS.

5. The external NMOS, choose the I(D) value 8-12 times higher than the output current at least.

外置

MOS的标称耐流要比实际的输出电流高8-12倍,譬如输出1A, 建议选择10A的MOS.

6. In order to reduce output ripple, the output capacitor should be larger than 220uF.

为了得到更好的输出纹波

,输出电容别小于220uF.

7. In order to reduce the heat, use more ground area all around PCB.

为了得到更好的散热

8.

Vout = 0.8V * (1 + R3/R2)

R2 = 47K ~ 82K

如果是

12-24V输入, 输出5V,6-8A的应用, 除了电感有足够的余量,NMOS建议选用

,二极管要能达

到接近

10A.

10. C7 and R4 are also necessary for loop stable and EMC pass.

C7与R4也是环路工作稳定与过EMC必不可少的小贴片器件.

11. Here below the PCB reference, support both TO252 or SOP8 N-MOSFET.

如下是同时支持

TO252与SOP8的NMOS的参考PCB图。

HM3123