This circuit note CN-0260 introduces an oversampled SAR ADC with PGA achieving greater than 125 dB dynamic range using AD7985, AD8253, AD8021, ADA4004-2 and ADR439.
The document presents a wide dynamic range signal conditioning circuit designed for applications requiring both high resolution and fast update rates, such as weighing scales or vibration monitoring. The solution combines an autoranging programmable gain instrumentation amplifier (PGA) with an oversampled successive-approximation register (SAR) ADC.
The system achieves a dynamic range of more than 125 dB.
The circuit uses an AD7985 ADC and an AD8253 PGA.
For small signal inputs, a gain of 100 is programmed to increase the effective signal-to-noise ratio.