This paper demonstrates that a 20-bit subrange ADC for high precision voltage measurement can be implemented with standard ATE resource and BOST circuits, without special devices. Our prototype 20-bit ADC employs subranging architecture and consists of a 16bit ADC (LTC1867), a 20-bit DAC (ADC5791), Arduino and some additional circuits. Its operation has been confirmed with simulations and experiments, and effects of non-idealities for each circuit to the overall 20-bit ADC performance have been evaluated. We consider that a 16bit audio-band digitizer in an ATE system can be used as the 16bit ADC while the 20-bit DAC as well as an error amplifier (another component for the subranging ADC) can be implemented with BOST circuits.