AD4129-8

Product Details

The AD4129-8 is an ultra-low power, high precision, measurement solution for low bandwidth battery operated applications. The fully integrated analog front end (AFE) includes a multiplexer for up to 16 single-ended or eight differential inputs, programmable gain amplifier (PGA), 16-bit sigma-delta (Σ-Δ) analog-to-digital converter (ADC), on-chip reference and oscillator, selectable filter options, smart sequencer, sensor biasing and excitation options, diagnostics, and newly added features to improve the battery-operated lifetime (more than five years on a coin cell), i.e., a first in, first out (FIFO) buffer and duty cycling.

The AD4129-8 allows to measure low frequency signals with a current consumption of 28.5 μA (gain = 1) and 32.5 μA (gain = 128) while continuously converting, and even lower average currents when using one of the duty cycling options. Configure the AD4129-8 to have eight differential inputs or 16 single-ended or pseudodifferential inputs, which connect to a crosspoint multiplexer, where any input pair can become a measurement channel input to the PGA and ADC.

The AD4129-8 is designed to operate from a single analog supply voltage from 1.71 V to 3.6 V. In battery applications, operation as low as 1.71 V can extend the system lifetime as the AFE can continue its operation, even as the battery voltage dissipates. The digital supply can be separate and range from 1.65 V to 3.6 V. Together with the reduced current consumption, use the integration of an on-chip FIFO buffer in tandem with the smart sequencer, to enable the AD4129-8 to become an autonomous measurement system, which allows the microcontroller to sleep for extended periods.

Intelligent interrupt functionality gives greater confidence in both error detection and safety. Enable an interrupt signal to trigger when the samples in the FIFO reach a predefined value or when a user programmable threshold is exceeded.

The AD4129-8 offers the following key analog functions to allow simple and effective connection to transducers used for measuring temperature, load, and pressure:

• PGA. Due to the programmable gain (from 1 to 128) and the high input impedance with low input current, the PGA allows direct interfacing to transducers with low output amplitudes like resistive bridges, thermocouples, and resistance temperature detectors (RTDs).
• The capacitive PGA allows full common-mode input range, giving designers greater margin to widely vary input common modes. A wider common-mode input range improves the overall resolution and is highly effective in ratiometric measurements.
• Low drift precision current sources. Use the IEXC0 and IEXC1 current source to excite 2‑, 3‑, and 4‑wire RTDs. Excitation current output options include 100 nA, 10 μA, 20 μA, 50 μA, 100 μA, 150 μA, and 200 μA.
• Use the low-side power switch (PDSW) to power down bridge sensors between conversions. Control the PDSW within the sequencer on a per channel basis, allowing optimum timing and energy savings in the overall system. The PDSW can also allow higher powered analog sensors to be used in a low power system.
• Voltage bias for thermocouples (the V_BIAS source sets the common-mode voltage of a channel to AV_DD/2).
• The smart sequencer allows the conversion of each enabled
  preconfigured channel in a predetermined order, allowing a mix of transducer, system checks, and diagnostic measurements to be interleaved. The sequencer eliminates the need for repetitive serial interface communication with the device. Configure sixteen channels in the sequence, each of them selecting from eight predefined ADC setups that allow the selection of gain, filter type, output data rate, buffering, timing, and reference source. High levels of integrated front-end functionality coupled with small package options allow smaller end solutions. For example, the AD4129-8 integrates a low thermal drift band gap reference in addition to accepting an external differential reference, which can be internally buffered.

In safety critical applications, the AD4129-8 includes diagnostic functionality such as open wire detection through burnout currents, internal temperature sensor, reference detection, and analog input overvoltage and undervoltage detection. The digital interface has added diagnostics like cyclic redundancy check (CRC) and serial interface checks for a robust communication link.

APPLICATIONS

• Smart transmitters
• Wireless battery and harvester powered sensor nodes
• Portable instrumentation
• Temperature measurement: thermocouple, RTD, thermistors
• Pressure measurement: bridge transducers
• Healthcare and wearables