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Data Sheet

ADAS3023

THEORY OF OPERATION

OVERVIEW

The ADAS3023 is a 16-bit, 8-channel simultaneous system on a

single chip that integrates the typical components used in a data

acquisition system in one easy to use, programmable device. It is

capable of converting two channels simultaneously up to 500,000

samples per second (500 kSPS) throughput. The ADAS3023

features

•

High impedance inputs

•

High common-mode rejection

•

An 8-channel, low leakage track and hold

•

A programmable gain instrumentation amplifier (PGIA)

with four selectable differential input ranges from ±2.56 V

to ±20.48 V

•

A 16-bit PulSAR® ADC with no missing codes

•

An internal, precision, low drift 4.096 V reference and

buffer

The ADAS3023 uses the Analog Devices patented high voltage

iCMOS process allowing up to a ±20.48 V differential input voltage

range when using ±15 V supplies, which makes the device suitable

for industrial applications.

The device is housed in a small 6 mm × 6 mm, 40-lead LFCSP

package and can operate over the industrial temperature range of

−40°C to +85°C. A typical discrete multichannel data acquisition

system containing similar circuitry requires more space on the

circuit board than the ADAS3023. Therefore, advantages of the

ADAS3023 solution include a reduced footprint and less complex

design requirements, leading to faster time to market and lower costs.

OPERATION

The analog circuitry of the ADAS3023 consists of a high

impedance, low leakage, track-and-hold PGIA with a high

common-mode rejection that can accept the full-scale differ-

ential voltages of ±2.56 V, ±5.12 V, ±10.24 V, and ±20.48 V (see

Figure 15). The ADAS3023 can be configured to sample two,

four, six, or eight channels simultaneously.

The ADAS3023 offers true high impedance inputs in a differential

structure and rejects common-mode signals present on the inputs.

This architecture does not require additional input buffers (op

amps) that are usually required for signal buffering, level shifting,

amplification, attenuation, and kickback reduction when using

switched capacitor-based SAR ADCs.

Digital control of the programmable gain setting of each

channel input is set via the configuration (CFG) register.

The conversion results are output in twos complement format

on the serial data output (SDO) and through an optional secondary

serial data output on the BUSY/SDO2 pin. The digital interface

uses a dedicated chip select (CS) to control data access to and

from the ADAS3023 together with a BUSY/SDO2 output, asyn-

chronous reset (RESET), and power-down (PD) inputs.

The internal reference of the ADAS3023 uses an internal temper-

ature compensated 2.5 V output band gap reference, followed by

a precision buffer amplifier to provide the 4.096 V high precision

system reference.

All of these components are configured through a serial (SPI-

compatible), 16-bit CFG register. Configuration and conversion

results are read after the conversions are completed.

The ADAS3023 requires a minimum of three power supplies

+15 V, −15 V, and +5 V. Internal low dropout regulators provide

the necessary 2.5 V system voltages that must be decoupled

externally via dedicated pins (ACAP, DCAP, and RCAP). The

ADAS3023 can be interfaced to any 1.8 V to 5 V digital logic

family using the dedicated VIO logic level voltage supply (see

Table 9).

A rising edge on the CNV pin initiates a conversion and changes

the ADAS3023 from track to hold. In this state, the ADAS3023

performs the analog signal conditioning and conversion. When

the signal conditioning is completed, the ADAS3023 returns to

the track state while, at the same time, quantizes the sample. This

two-tiered process satisfies the necessary settling time requirement

and achieves a fast throughput rate of up to 500 kSPS with 16-bit

accuracy.

Figure 35. Simplified Block Diagram

BUF

REF

LOGIC/

INTERFACE

TRACK

AND

HOLD

PGIA

PulSAR

ADC

DIFF TO

COM

IN0

CNV

SCK

DIN

SDO

REFIN

BUSY

IN1

IN2

IN3

IN4

IN5

IN6

IN7

COM

VDDH AVDD DVDD

VIO

RESET

REFx

DGND

AGND

VSSH

ADAS3023

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