The AD7730 is a complete analog front end for weigh-scale and
pressure measurement applications. The device accepts lowlevel 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.
FASTStep is a trademark of Analog Devices, Inc.
DAC SERIAL INTERFACE
AND CONTROL LOGIC
SIGMA-DELTA A/D CONVERTER
AGND DGND POL RDY RESET
AVDD DVDD REF IN(–) REF IN(+)
The modulator output is processed by a low pass programmable
digital filter, allowing adjustment of filter cutoff, output rate and
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 AD7730 is available in a 24-pin plastic DIP, a 24-lead
SOIC and 24-lead TSSOP package. The AD7730L is available
in a 24-lead SOIC and 24-lead TSSOP package.