AD7730 Application Note

●Product Details

●The AD7730 is a complete analog front end for weigh-scale and pressure measurement applications. The device accepts low-level signals directly from a transducer and outputs a serial digital word. The input signal is applied to a proprietary programmable gain front end based around an analog modulator. The modulator output is processed by a low pass programmable digital filter, allowing adjustment of filter cutoff, output rate and settling time.

●The part features two buffered differential programmable gain analog inputs as well as a differential reference input. The part operates from a single +5 V supply. It accepts four unipolar analog input ranges: 0 mV to ±10 mV, +20 mV, +40 mV and +80 mV and four bipolar ranges: ±10 mV, ±20 mV, ±40 mV and ±80 mV. The peak-to-peak resolution achievable directly from the part is 1 in 230,000 counts. An on-chip 6-bit DAC allows the removal of TARE voltages. Clock signals for synchronizing ac excitation of the bridge are also provided.

●The serial interface on the part can be configured for three-wire operation and is compatible with microcontrollers and digital signal processors. The AD7730 contains self-calibration and system calibration options, and features an offset drift of less than 5 nV/°C and a gain drift of less than 2 ppm/°C. The part is available in a 24-pin plastic DIP, a 24-lead SOIC and 24-lead TSSOP package.

●### Features and Benefits

● Resolution of 230,000 Counts (Peak-to-Peak)

● Offset Drift: 5 nV/°C

● Gain Drift: 2 ppm/°C

● Line Frequency Rejection: >150 dB

● Buffered Differential Inputs

● Programmable Filter Cutoffs

● Specified for Drift Over Time

● Operates with Reference Voltages of 1 V to 5 V