Abstract: An analog to digital conversion device integrated in a microcontroller that is accomplished on a single chip, the device comprising: an adjustable gain amplifier, used to obtain a corresponding analog voltage signal V1—V2 after corresponding an input analog voltage V1 to a reference voltage V2, and based on a corresponding relationship of a gain function A, performing an amplification operation to a corresponding analog voltage signal, and further outputting an amplified analog voltage signal A(V1−V2); and a n-bit analog to digital converter, having a reference voltage Vr, electrically coupling to an output of the adjustable gain amplifier, used to convert the amplified analog voltage signal into a digital voltage signal, and outputting the digital voltage signal, wherein the gain function of the adjustable gain amplifier can be provided to the microcontroller to perform an adjustment according to the reference voltage Vr and a relationship of a peak value of the input corresponding analog voltage