ADI AD5940BCBZ-RL7

The AD5940 is a high-precision, low-power AFE designed for portable applications requiring high-accuracy electrochemical measurement techniques, such as current, voltammetric, or impedance measurements. It is designed for skin impedance and body impedance measurements, and for use with the AD8233 AFE in complete biopotential measurement systems. Designed for electrochemical toxic gas detection. The AD5940 includes two high-precision excitation loops and a general-purpose measurement channel for a wide range of measurements on the sensor under test. The first excitation loop comprises an ultralow power, dual-output DAC and a low-power, low-noise potentiostat. One output of the DAC controls the noninverting input of the potentiostat, and the other output controls the noninverting input of the TIA. This low-power excitation loop is capable of generating signals from DC to 200 Hz. The second excitation loop includes a 12-bit DAC, referred to as the high-speed DAC. This DAC is capable of generating high-frequency excitation signals up to 200 kHz. The AD5940 measurement channel features a 16-bit, 800 kSPS multichannel SAR ADC with input buffers, a built-in antialiasing filter, and a PGA. An input multiplexer at the ADC front end allows users to select input channels for measurement. These input channels include multiple external current inputs, external voltage inputs, and internal channels. Using the internal channels, diagnostic measurements of internal supply voltage, die temperature, and voltage reference can be performed. The current inputs include two TIAs with programmable gain and load resistors for measuring different sensor types. The first TIA, referred to as the low-power TIA, measures low-bandwidth signals. The second TIA, referred to as the high-speed TIA, measures high-bandwidth signals up to 200 kHz. An ultralow leakage, programmable switch matrix connects the sensor to the internal analog excitation and measurement modules. This matrix provides an interface for connecting external RTIA and calibration resistors. The matrix can also be used to multiplex multiple electrochemical measurement devices to the same wearable electrodes. On-chip precision voltage references of 1.82 V and 2.5 V are provided. The internal ADC and DAC circuits use these on-chip references to ensure low-drift performance for both 1.82 V and 2.5 V peripherals. The AD5940 measurement module can be controlled via direct register writes through the SPI interface, or through a preprogrammed sequencer that provides autonomous control of the AFE. 6 kB of SRAM is partitioned into a deep data FIFO and a command FIFO. Measurement commands are stored in the command FIFO and measurement results are stored in the data FIFO. Multiple FIFO-related interrupts are available to indicate when the FIFO is full. Multiple GPIOs are provided and controlled using the AFE sequencer for precise periodic control of multiple external sensor devices. The AD5940 operates from a 2.8 V to 3.6 V supply and is rated over a temperature range of -40°C to +85°C. The AD5940 is available in a 56-lead, 3.6 mm × 4.2 mm WLCSP package.

• Low-bandwidth loop EDA bioimpedance measurement
• High-bandwidth loop BIA measurement
• High-precision potentiostat configuration
• Bioimpedance and ECG measurement with AD5940, AD8232, and AD8233
• Smart water/liquid quality AFE