The LTC 1594/LTC1598 are micropower, 12-bit sampling A/D converters that feature 4- and 8-channel multiplexers, respectively. They typically draw only 320A of supply current when converting and automatically power down to a typical supply current of 1nA between conversions. The LTC1594 is available in a 16-pin SO package and the LTC1598 is packaged in a 24-pin SSOP. Both operate on a 5V supply. The 12-bit, switched-capacitor, successive approximation ADCs include a sample-and-hold. On-chip serial ports allow efficient data transfer to a wide range of microprocessors and microcontrollers over three or four wires. This, coupled with micropower consumption, makes remote location possible and facilitates transmitting data through isolation barriers. The circuit can be used in ratiometric applications or with an external reference. The high impedance analog inputs and the ability to operate with reduced spans (to 1.5V full scale) allow direct connection to sensors and transducers in many applications, eliminating the need for gain stages.