Patent ID: 7061422

Claim:
An analog-to-digital (A/D) converting device for converting an analog signal into a digital signal, the A/D converting device comprising: a reference voltage generating circuit for dividing a first predetermined voltage to generate M primary reference voltages which are sorted based on the voltage level, and for dividing the (M−1) th primary reference voltage to generate N secondary reference voltages which are sorted based on the voltage level, wherein the M th primary reference voltage is equal to the first predetermined voltage, the N th secondary reference voltage is equal to the (M−1) th primary reference voltage, and M and N are positive integers; a primary A/D converting circuit coupled to the reference voltage generating circuit for comparing the analog signal with each of the primary reference voltages to generate a most significant bits (MSBs); and a secondary A/D converting circuit coupled to the reference voltage generating circuit and the primary A/D converting circuit for comparing the analog signal, the MSBs, the primary reference voltages, and the secondary reference voltages to generate a least significant bits (LSBs); wherein, the digital signal is obtained from the MSBs and the LSBs.