AD7798

The AD7798/AD7799 is a low power, complete analog front end for low frequency measurement applications. The device contains a low noise 24-bit (AD7799)/ 16-bit (AD7798) - ADC with three differential inputs. The on-chip low noise instrumentation amplifier means that signals of small amplitude can be interfaced directly to the ADC. With a gain setting of 64, the rms noise is 80 nV for AD7798 and 65 nV for the AD7799 at 16.6 Hz.

The device contains a low side power switch which is useful in bridge applications. The switch allows the bridge to be disconnected from the power supply when conversions are not being performed and this will minimise power consumption. The device also has 100 nA burnout currents. These currents are used to detect if sensors connected to the analog inputs are burnt out. Other on-chip features include an internal clock so the user does not have to supply a clock to the device. This reduces the component count in a system and provides board
space savings. The update rate is programmable on the AD7798/99. It can be varied from 4 Hz to 500 Hz.

The part operates with a single power supply from 2.7 V to 5.25 V. It consumes a current of 380 uA maximum for the AD7798 and 450 uA maximum for the AD7799. The AD7799/AD7798 is housed in a 16-lead TSSOP package.