The circuit shown in Figure 1 is a highly integrated, 16-bit, 1 MSPS, multiplexed, 8-channel, flexible digital acquisition system (DAS) with integrated programmable gain instrumentation amplifier (PGIA) capable of handling the full range of industrial Signal.

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 LSBINL 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, eliminating the need for additional buffering; buffering is typically used to reduce the SAR analog-to-digital converter (ADC) based on a capacitive digital-to-analog converter (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 it ideal for low sampling rate battery-powered applications.

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 AD8031 low-noise voltage reference buffered by the ADR434 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-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.

The ADAS3022 is the first complete DAS on a single chip capable of conversion at rates up to 1 MSPS and accepts differential analog input signals up to ±24.576V. 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.

ADAS3022 integrates PGIA internally 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. The input range is 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 4.096V ADR434. The ADR434 features high accuracy, low power consumption (800μA 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 a 4-wire serial interface (span style="text-decoration: overline;">CS, SDO, SCK and DIN).

ADP1613 power supply design

The ADP1613 is used as a single-ended primary inductor (SEPIC) Cuk converter to provide the ADAS3022 with the required high voltage supply of ±15 V at 20 mA and a low output ripple of 3 mV maximum when powered from an external 5 V supply. Ideal for waves. In this application, the ADP1613 switches at 1.3 MHz. As shown in Figure 2, the ADP1613 minimizes the number of external components and has an efficiency of over 86%, so it meets the specifications of ADAS3022. The biggest advantage of using the low-cost ADP1613 in this topology is its excellent tracking ability between the two supply rails while producing ±15 V using off-the-shelf coupled inductors. In addition, design and manufacturing can be completed easily and quickly through the ADIsimPower design tool.

The circuit shown in Figure 1 was designed using the following inputs from the ADP161x SEPIC-Cuk downloadable design tool, available from ADIsimPower:

• V _INMIN = 4.75 V
• V _INMAX = 4.99 V
• V _OUT = 15 V
• VRIPPLE ₌ 0.02%
• Ambient temperature = 55°C
• Optimize for lowest cost
• External filter options

Note that the maximum voltage on the SW pin of the ADP1613 is: VIN + VOUT = 20 V, which is below its absolute maximum voltage specification of 21 V. For input voltages greater than or equal to 5 V, the design tool recommends using a series N-channel MOSFET driven from the SW pin. With a 1 V safety margin, this circuit eliminates the need for FETs for up to 5.25 V input and 15 V output. Therefore, the input voltage used in the design tool is set to 4.99 V. The design results for the ADP1613 SEPIC-Cuk converter can be found in the CN0201-Design Support Package .

dynamic performance

Figure 3 shows the typical dynamic performance of the ADAS3022 in the presence of an AC input signal. In the test, the ADAS3022 was driven by a linear ±15 V bench power supply and the ±15 V output of the ADP1613 evaluation board, and no difference in AC or DC performance was observed.