20-bit sigma-delta ADC with on-chip PGA
The AD7781BRUZ-REEL is a 20-bit sigma-delta analog-to-digital converter from Analog Devices, integrating a programmable gain amplifier (PGA) ahead of the modulator for direct connection to low-level differential signals from bridge sensors, load cells, or thermocouples. With a sampling rate of 16.7 SPS, the on-chip digital filter settles to full resolution at that update rate — the output word rate is the same as the filter's first notch frequency, which also provides 50 Hz and 60 Hz rejection when the notch is placed at those line frequencies.
The external reference input (REFIN) sets the analog input span; the reference voltage must be stable and low-noise because the 20-bit resolution resolves down to the sub-µV level per LSB at a 2.5 V reference.
Package and interface
Housed in a 16-lead TSSOP (4.40 mm body width, 0.65 mm pitch), the AD7781BRUZ-REEL fits a compact PCB footprint — the 0.65 mm pitch routes out on a two-layer board with standard trace widths. The SPI data interface uses four wires (SCLK, DIN, DOUT, CS) and operates up to several MHz, though the output data rate is capped at 16.7 SPS by the internal filter — the SPI bus is used to read conversion results and write configuration registers, not to clock out raw modulator data. Available in Tape & Reel (TR) or Cut Tape (CT) for pick-and-place assembly; the REEL suffix indicates reel packaging for automated production lines.
ROHS3 compliant with no exemptions; the part ships lead-free and meets the EU RoHS directive for unrestricted global distribution.