What the AD7705BRUZ-REEL is and where it fits
The Analog Devices AD7705BRUZ-REEL is a 16-bit sigma-delta ADC in a 16-TSSOP package, built around a MUX-PGA-ADC architecture. It accepts two differential inputs through an on-chip multiplexer and programmable gain amplifier (PGA), then digitises at a maximum sampling rate of 500 SPS. The serial interface supports SPI and DSP protocols, so it ties directly to the SPI port of most microcontrollers or DSPs without external logic. The dual supply range — 2.7 V to 3.3 V or 5 V on both analog and digital rails — means it can run from a single 3.3 V or 5 V supply in many designs. The industrial temperature grade of -40°C to 85°C suits it for factory-floor instrumentation, weigh scales, pressure transmitters, and other low-speed precision measurement applications.
500 SPS — what the sampling rate means for the design
At 500 SPS this is a low-bandwidth ADC, not a high-speed acquisition part. The 16-bit resolution and sigma-delta architecture trade conversion speed for noise rejection.
Package and supply — what to check on the layout
The 16-TSSOP body is 4.40 mm wide — a compact footprint that fits tight analog front-end sections. The supply pins accept 2.7 V to 3.3 V or 5 V on both analog and digital sides, so a single 3.3 V rail works if the reference voltage and input signals stay within that range. The reference is external (not on-chip), so the layout needs a clean reference voltage source — a precision shunt or series reference — placed close to the REF IN pins. The SPI/DSP interface runs at the master clock rate; keep the serial clock trace short and away from the analog input traces to avoid coupling noise into the sigma-delta modulator.