The AD7843 is a 12-bit successive approximation ADC with a synchronous serial interface and low on resistance switches for driving touch screens. The part operates from a single 2.2 V to 5.25 V power supply and features throughput rates greater than 125 kSPS. The external reference applied to the AD7843 can be varied from 1 V to +VCC， while the analog input range is from 0 V to VREF. The device includes a shutdown mode that reduces the current consumption to less than 1 μA. The AD7843 features on-board switches. This， coupled with low power and high speed operation， make this device ideal for battery-powered systems such as personal digital assistants with resistive touch screens， and other portable equipment. The part is available in a 16-lead 0.15“ quarter size outline package （QSOP） and a 16-lead thin shrink small outline package （TSSOP）。