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lmzm33603芯片发热,效率低问题



lmzm33603,输入电压28V,电流85mA,输出电压5.5V,电流244mA,效率58.4%,实测芯片表面温度55度

空载时输出电压正常,28V电源电流很小,芯片不烫;下图是手册中24V输入电压效率图,5.5V/244mA输出效率也不至于58%这么低吧,芯片温度确实高,因测试条件有限,没有用电子负载测试电流增大后功效

当接上磁珠供电后,芯片很烫,下图是原理图和PCB,请您帮忙看下

是否是设计压差大导致损耗也很大(原理图中C102已经由0.1uF更换为100pF,解决了输出电压偏离目标值问题)