最大2A电流，如何选择宽长比的啊，或者数并联管子个数？

wang.bin

请教你一个问题：你们在用NMOS管做开关时，开关流过最大2A电流，如何选择宽长比的啊，或者说并联管子个数？

122013137

用NMOS管做开关啊

wang.bin

回复 2# 122013137


那用啥做开关？

wang.bin

The θja parameter is usually most relevant for packages where a heat sink isn't used. The θja is specified on the datasheet for each product. A heat sink would be required if max power is exceeded

Pmax = (Tjmax - Ta) / θja, where Ta = ambient temperature
Tjmax = 150C for the ADM3232E, I don't support the ADM3074E but suspect it will be between 125C and 150C.

Therefore, based on the ambient temperature of the system you can calculate if a heat sink is required. i.e. if actual power dissipation on the device exceeds calculated max power dissipation.

θjc is usually only used in cases where a heat sink is used or where most or all of the heat is dissipated through the surface in consideration. θjc for the ADM3232EARUZ will be approximately 30degC/W. I believe θjc for the ADM3047EARZ will be approx 45degC/W based on the package.

Tc is the package case temperature and is measured at the hottest point on the package.

king0798

过这么大的电流，主要关心的是功耗和发热。
mos管上的压降越大，损耗在mos管上的功耗就越多。如果根据功耗要求，比如mos管的导通电阻是0.1Ω符合要求，那么压降是0.2V。功耗是0.4W。算封装热阻是100℃/W，那温升是40℃，加上环境温度，芯片的温度达到了105℃。那就要求在这个温度下nmos管导通阻抗是0.1Ω。根据此选择nmos尺寸。