Datasheet

ADAS3022 Data Sheet
Rev. B | Page 22 of 40
THEORY OF OPERATION
OVERVIEW
The ADAS3022 is the first system on a single chip that integrates
the typical components used in a data acquisition system in one
easy to use, programmable device. This single-chip solution is
capable of converting up to 1,000,000 samples per second
(1 MSPS) of aggregate throughput. The ADAS3022 features
• High impedance inputs
• High common-mode rejection
• 8-channel, low crosstalk multiplexer (mux)
• Programmable gain instrumentation amplifier (PGIA) with
seven selectable differential input ranges from ±0.64 V to
±24.576 V
• 16-bit PulSAR® ADC with no missing codes
• Internal, precision, low drift 4.096 V reference and buffer
• Temperature sensor
• Channel sequencer
The ADAS3022 uses an Analog Devices patented high voltage
iCMOS® process, allowing up to a ±24.576 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
and can operate over the industrial temperature range (−40°C
to +85°C). A typical discrete multichannel data acquisition
system containing similar circuitry would require at least three
times more space on the circuit board. Therefore, advantages of
the ADAS3022 solution include reduced footprint and less
complex design requirements, which also results in faster time
to market and lower cost.
ADAS3022 OPERATION
As shown in Figure 51, the ADAS3022 internal analog circuitry
consists of a high impedance, low leakage multiplexer and a
programmable gain instrumentation amplifier that can accept
full-scale differential voltages of ±0.64 V, ±1.28 V, ±2.56 V, ±5.12 V,
±10.24 V, ±20.48 V, and ±24.576 V. The ADAS3022 can be con-
figured to use up to eight single-ended input channels or four
pairs of channels, that is, 125 kSPS per channel for eight channels
or effectively 250 kSPS for four channel pairs. The device can also
provide a relative temperature measurement using the internal
temperature sensor. In addition, the differential auxiliary channel
pair (AUX+ and AUX−) is provided with the specified input
range of ±V
REF
. This option bypasses the mux and PGIA stages,
allowing direct access to the SAR ADC core.
Reducing the number of channels or pairs increases the throughput
rate by an amount proportional to the reciprocal of the number
of sampled channels multiplied by the aggregate throughput:
1/(Number of Channels or Pairs) × 1000 kSPS
For a single channel or channel pair, the maximum throughput
rate is 1 MSPS. For all eight channels, the AUX channel pair, and
the temperature sensor, the throughput rate of a given channel
decreases to 100 kSPS.
IN4
IN5
IN3
IN2
BUF
IN6
IN7
IN1
IN0
IN0/IN1
PAIR
DIFF TO
DIFF
COM
IN2/IN3
IN4/IN5
IN6/IN7
PulSAR
ADC
LOGIC/
INTERFACE
REFIN
REF
REFx
CNV
RESET PD
SCK
DIN
SDO
VSSH
VDDH
AGND
VIO
DVDD
AVDD
DGND
CS
COM
AUX+
AUX–
BUSY
ADAS3022
MUX
TEMP
SENSOR
10516-005
PGIA
Figure 51. ADAS3022 Simplified Block Diagram