5V single power supply 8-channel data acquisition system circuit design

　　Circuit Features and Benefits: The circuit shown in Figure 1 is a highly integrated, 16-bit, 1 MSPS, multiplexed, 8-channel, flexible digital acquisition system (DAS) with an integrated programmable gain instrumentation amplifier (PGIA) that can Processes a full range of industrial-grade signals. Powering the circuit from a single +5 V supply, a high-efficiency, low-ripple boost converter generates ±15 V and can handle differential input signals up to ±24.576 V (±2 LSB INL maximum, ±0.5 LSB DNL typical) . For high-precision applications, this compact, cost-effective circuit provides high accuracy and low noise performance. Successive approximation register (SAR)-based data acquisition systems integrate true high-impedance differential input buffers, thus eliminating the need for additional buffering; buffering is typically used to reduce SAR analog-to-digital converters (ADCs) based on capacitive digital-to-analog converters (DAC) The resulting backlash. In addition, the circuit's high common-mode rejection eliminates the need for an external instrumentation amplifier, which is typically required in applications where common-mode signals are present.

　　The ADAS3022 is a complete 16-bit, 1 MSPS data acquisition system integrating: an 8-channel, low-leakage multiplexer; a programmable gain instrumentation amplifier stage with high common-mode rejection; and a precision low-drift 4.096 V reference voltage source; a reference voltage buffer; and a high-performance, latency-free, 16-bit SAR ADC. The ADAS3022 reduces power consumption at the end of each conversion cycle, so operating current and power consumption scale linearly with throughput rate, making This makes it ideal for battery-powered applications with low sampling rates. ADAS3022 integrates 8 inputs and 1 COM input; the COM input can be configured as 8 single-ended channels, 8 channels referenced to the same reference voltage, 4 differential channels, or different combinations of single-ended and differential channels. In the circuit shown in Figure 1, the ADR434 low-noise voltage reference buffered by the AD8031 op amp provides the reference voltage. The AD8031's ability to drive dynamic loads with fast recovery makes it ideal for use as a reference buffer.

　　The ADP1613 is a dc-to-dc boost converter with an integrated power switch that provides the ADAS3022 with the ±15 V high voltage power required for the on-chip input multiplexer and programmable gain instrumentation amplifier without affecting the performance of the ADAS3022. This circuit uses a combination of ADAS3022, ADP1613, ADR434, and AD8031 precision devices to provide both high accuracy and low noise performance.

　　Circuit Description: The first complete DAS on a single chip capable of conversion at rates up to 1 MSPS and accepting differential analog input signals up to ±24.576 V. The device requires high-voltage bipolar supplies: ±15 V (VDDH and VSSH), +5 V (AVDD and DVDD), and +1.8 V to +5 V (VIO). The ADAS3022 eliminates the need for signal buffering, level translation, amplification, noise suppression, and other analog signal conditioning found in standard solutions, simplifying the design challenges of precision 16-bit, 1 MSPS DAS. In addition, the ADAS3022 provides better timing and noise performance at higher data rates, smaller size, faster time to market, and lower price.

　　The ADAS3022 integrates PGIA and can set the gain to 0.16, 0.2, 0.4, 0.8, 1.6, 3.2 and 6.4, and the full differential input range it can handle is ±24.576 V, ±20.48 V, ±10.24 V, ±5.12 V, respectively. ±2.56 V, ±1.28 V, and ±0.64 V. Input ranges are referenced to the internal 4.096 V reference. It measures pseudo-differential, unipolar, and bipolar input ranges relative to the input voltage on the COM pin. In the circuit shown in Figure 1, the external reference voltage is provided by the 4.096 V ADR434. The ADR434 features high accuracy, low power consumption (800 µA operating current), low noise, ±0.12% maximum initial error, and excellent temperature stability. The AD8032 low-power op amp for buffering external reference voltages is ideal whether in battery-powered systems with high bandwidth requirements or in high-speed systems with high component density and low power requirements. The ADAS3022 digital interface consists of asynchronous inputs (CNV, RESET, PD and BUSY) and an SPI, FPGA or DSP compatible 4-wire serial interface (CS, SDO, SCK and DIN) for reading back conversion results and programming configuration registers composition.