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LM76003: LM76003RNPT 的VFB电压不准,负载增大而下降

Part Number: LM76003


    您好!

    我用了LM76003RNPT 的Buck,

input:24V,output:3.3V

有的板子能带2.5A 电压维持不变,有点板子1A电压往下降,量得VFB电压也下降了。电流越大电压降低越多,有的降低2.2V,这会是PCB layout 问题吗?还是物料有问题?原理图如下:

我把电感换成4.7uH,output电容去掉MLCC,input电容减掉一半,修改频率等措施,效果不大。

FB分压电阻在top层, LM76003芯片在bot层,有时候重新焊接一下FB电阻,能稳定电压的负载电流可以大一点,有时候重新焊机后负载电流又变小了。