LM3940ISX LM3940ISX-12 LM3940ISX-3.3 LM3940ISX-3.3 03+ LM3940ISX-3.3 NOPB LM3940ISX-3.3 电源IC LM3940ISX-3.3/NOPB LM3940ISX-3.3+ LM3940ISX-3.3NOPB LM3940ISX-3.3V