This work presented a trimming technique and algorithm applied in a capacitive successive approximation register(SAR) analog to digital converter(ADC) for a sensor interface, which can be integrated with the preceding sensor and the following controlling circuit. Without spending a special calibration phase or adding complicated functions, this circuit keeps a 12-bit resolution by trimming the capacitor array. Its merits of low power and small area make it suitable to be embedded in a power and cost sensitive system such as a battery-supplied sensor network node. The prototype 12-bit ADC is implemented by 0.5 m 2P3M CMOS technology, with the wide supply range of 2–5 V, its power consumption is only 300 A at a sampling speed of 200 kHz. This work presented a trimming technique and algorithm applied in a moving two-phase approximation register (SAR) analog to digital converter (ADC) for a sensor interface, which can be integrated with the preceding sensor and the following controlling circuit. or adding complicated functions, this circuit keeps a 12-bit resolution by trimming the capacitor array. Its merits of low power and small area make it suitable to be embedded in a power and cost sensitive system such as a battery-supplied sensor network node. The prototype 12-bit ADC is implemented by 0.5 m 2 P3M CMOS technology, with a wide supply range of 2-5 V, its power consumption is only 300 A at a sampling speed of 200 kHz.