GENERAL DESCRIPTION

The AD4130-8 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), 24-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 5 years on a coin cell), that is, a first in, first out

(FIFO) buffer and duty cycling.

The AD4130-8 allows users 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. The AD4130-8

can be configured to have 8 differential inputs or 16 single-ended or

pseudo differential inputs, which connect to a crosspoint multiplexer,

where any input pair can become a measurement channel input

to the PGA and ADC.

The AD4130-8 is designed to allow the user 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, the integration of

an on-chip FIFO buffer can be used in tandem with the smart

sequencer, to enable the AD4130-8 to become an autonomous

measurement system, which allows the microcontroller to sleep for

extended periods.

Intelligent interrupt functionality gives the user a greater confidence

in both error detection and safety. The user can 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 following key analog functions are offered on the AD4130-8

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 for widely varying input common

modes. A wider common-mode input range improves the overall

resolution and is highly effective in ratio metric measurements.

► Low drift precision current sources. The IEXC0 and IEXC1 current

source can be used 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.

► The low-side power switch (PDSW) can be used to power down

bridge sensors between conversions. The PDSW can be controlled

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 VBIAS source sets the

common-mode voltage of a channel to AVDD/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 need for repetitive

serial interface communication with the device. Sixteen channels

can be configured in the sequence, each of them selecting from

eight predefined ADC setups that allow 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

AD4130-8 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 AD4130-8 includes diagnostic

functionality such as open wire detection via burnout currents,

internal temperature sensor, reference detection, and analog input

overvoltage and undervoltage detection. Added diagnostics are

included on the digital interface like cyclic redundancy check (CRC)

and serial interface checks for a robust communication link.

FEATURES

► Ultralow current consumption (typical):

► 32 μA: continuous conversion mode (gain = 128)

► 5 μA: duty cycling mode (ratio = 1/16)

► 0.5 μA: standby mode

► 0.1 μA: power-down mode

► Built-in features for system level power savings:

► Current saving duty cycle ratio: 1/4 or 1/16

► Smart sequencer and per channel configuration minimizes host processor load

► Deep embedded FIFO minimizes host processor load (depth of 256 samples)

► Autonomous FIFO interrupt functionality, threshold detection

► Single supply as low as 1.71 V increasing battery length

► RMS noise: 25 nV rms at 1.17 SPS (gain = 128) – 48 nV/√Hz

► Up to 22 noise free bits (gain = 1)

► Output data rate: 1.17 SPS to 2.4 kSPS

► Operates from 1.71 V to 3.6 V single supply or ±1.8 V split supplies

► Band gap reference with 15 ppm/°C maximum drift

► PGA with rail-to-rail analog input

► Adaptable sensor interfacing functionality:

► Matched programmable excitation currents for RTDs

► On-chip bias voltage generator for thermocouples

► Low-side power switch for bridge transducers

► Sensor open wire detection

► Internal temperature sensor and oscillator

► Self and system calibration

► Flexible filter options

► Simultaneous 50 Hz/60 Hz rejection (on selected filter options)

► General-purpose outputs

► Diagnostic functionality

► Crosspoint multiplexed inputs

► 8 differential/16 pseudo differential inputs

► 5 MHz SPI (3-wire or 4-wire)

► Available in 35-ball, 2.74 mm × 3.6 mm WLCSP

► Temperature range: −40°C to +105°C

APPLICATIONS

► Smart transmitters

► Wireless battery and harvester powered sensor nodes

► Portable instrumentation

► Temperature measurement: thermocouple, RTD, thermistors

► Pressure measurement: bridge transducers

► Healthcare and wearables