说明：  这个文件包含A3972的protel99 原理图和PCB图，经过大量产品验证。配合本人以前上传的A3972源程序，希望可以为初学者提供参考。本人是作者。陈先生13802939662
(This document contains protel99 the A3972 and PCB schematic diagram, a large number of products after verification. I used to upload with the A3972 source, hoping to provide a reference for beginners. I am a writer. Mr. Chen 13802939662)