AD4129-4数据手册ADI中文资料规格书

描述 Description

The AD4129-4 is an ultra-low power, high precision, and measurementsolution for low bandwidth battery-operated applications. Thefully integrated analog front end (AFE) includes a multiplexer forup to 8 single-ended or 4 differential inputs, programmable gainamplifier (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-operatedlifetime (more than 5 years on a coin cell), that is, a first in, first out(FIFO) buffer and duty cycling.

The AD4129-4 allows users to measure low-frequency signalswith a current consumption of 28.5 μA (gain = 1) and 32.5 μA(gain = 128) while continuously converting, and even lower averagecurrents when using one of the duty cycling options. The AD4129-4can be configured to have 4 differential inputs or 8 single-ended orpseudodifferential inputs, which connect to a crosspoint multiplexer,where any input pair can become a measurement channel input tothe PGA and ADC.

The AD4129-4 is designed to allow the user to operate from asingle analog supply voltage from 1.71 V to 3.6 V. In batteryapplications, operation as low as 1.71 V can extend the systemlifetime as the AFE can continue its operation, even as the batteryvoltage dissipates. The digital supply can be separate and rangefrom 1.65 V to 3.6 V.

Together with the reduced current consumption, the integration ofan on-chip FIFO buffer can be used in tandem with the smartsequencer, to enable the AD4129-4 to become an autonomousmeasurement system, which allows the microcontroller to sleep forextended periods.

Intelligent interrupt functionality gives the user a greater confidencein both error detection and safety. The user can enable an interruptsignal to trigger when the samples in the FIFO reach a predefinedvalue or when a user-programmable threshold is exceeded.

The following key analog functions are offered on the AD4129-4to allow simple and effective connection to transducers used formeasuring temperature, load, and pressure:


PGA. Due to the programmable gain (from 1 to 128) and thehigh input impedance with low input current, the PGA allowsdirect interfacing to transducers with low output amplitudes suchas resistive bridges, thermocouples, and resistance temperaturedetectors (RTDs).
The capacitive PGA allows full common-mode input range, givingdesigners greater margin for widely varying input commonmodes. A wider common-mode input range improves the overallresolution and is highly effective in ratio metric measurements.
Low drift precision current sources. The IEXC0 and IEXC1 currentsources 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 downbridge sensors between conversions. The PDSW can be controlledwithin the sequencer on a per channel basis, allowingoptimum timing and energy savings in the overall system. ThePDSW can also allow higher powered analog sensors to be usedin a low power system.
Voltage bias for thermocouples (the VBIAS source sets thecommon-mode voltage of a channel to AVDD/2).
The smart sequencer allows the conversion of each enabledpreconfigured channel in a predetermined order, allowing a mixof transducer, system checks, and diagnostic measurements tobe interleaved. The sequencer eliminates the need for repetitiveserial interface communication with the device. Sixteen channelscan be configured in the sequence, each of them selecting fromeight predefined ADC setups that allow selection of gain, filtertype, output data rate, buffering, timing, and reference source.
High levels of integrated front-end functionality, coupled with smallpackage options, allow smaller end solutions. For example, theAD4129-4 integrates a low thermal drift band gap reference inaddition to accepting an external differential reference, which canbe internally buffered.In safety critical applications, the AD4129-4 includes diagnosticfunctionality such as open-wire detection through burnout currents,internal temperature sensor, reference detection, and analog inputovervoltage and undervoltage detection. Added diagnostics areincluded on the digital interface such as cyclic redundancy check(CRC) and serial interface checks for a robust communication link.

特性 Features

Ultra-low 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 16 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
4 differential/8 pseudodifferential inputs
5 MHz SPI (3-wire or 4-wire)
Available in 32-lead, 5 mm × 5 mm LFCSP
Temperature range: −40°C to +125°C (LFCSP)
AD4129-4 LFCSP pin compatible with AD7124-4 LFCSP

应用 Application

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