Data Sheet

ADAS3023

Figure 38. Complete 5 V, Single-Supply, 8-Channel Data Acquisition System with PGIA

TYPICAL APPLICATION CONNECTION DIAGRAM

As shown in Figure 38, the ADP1613 is used in an inexpensive

SEPIC-Ćuk topology, which is an ideal candidate for providing

the ADAS3023 with the necessary high voltage ±15 V robust

supplies (at 20 mA) and low output ripple (3 mV maximum) from

an external 5 V supply. The ADP1613 satisfies the specification

requirements of the ADAS3023 using minimal external compo-

nents yet achieves greater than 86% efficiency. See the CN-0201

circuit note for complete information about this test setup.

ANALOG INPUTS

Input Structure

The ADAS3023 uses a differential input structure between each

of the channel inputs, IN0 to IN7, and a common reference

(COM), all of which sample simultaneously.

Figure 39 shows an equivalent circuit of the inputs. The diodes

provide ESD protection for the analog inputs (IN0 to IN7) and

COM from the high voltage supplies (VDDH and VSSH). Ensure

that the analog input signal does not exceed the supply rails by

more than 0.3 V because this can cause the diodes to become

forward-biased and to start conducting current. The voltages

beyond the absolute maximum ratings may cause permanent

damage to the ADAS3023 (see Table 4).

Figure 39. Equivalent Analog Input Circuit

Programmable Gain

The ADAS3023 incorporates a programmable gain instru-

mentation amplifier (PGIA) with four selectable ranges. The

PGIA settings are specified in terms of the maximum absolute

differential input voltage across an input pin and the COM pin,

for example INx to COM. The power on and default conditions

are preset to the ±20.48 V (PGIA = 11) input range.

Note that because the ADAS3023 can use any input type, such

as bipolar single-ended and pseudo bipolar, setting the PGIA is

important to make full use of the allowable input span.

IN0

IN1

IN2

IN3

IN4

IN5

IN6

IN7

DIFF TO

COM

LOGIC/

INTERFACE

REFIN

REF

CNV

RESET

SCK

DIN

SDO

VDDH

AVDD DVDD

VIO

CS

COM

BUSY

+

+

+

ENABLE

ADP1613

ADAS3023

COMP

FB

FREQ

EN

VIN

GND

SS

SW

+

+

+

+

VSSH

RF2

4.22kΩ

RF1B

47.5kΩ

100kΩ

12nF

10pF

1µF

1Ω

0Ω

DNI

1µF

Z1

1µF

D1

D2

C1

1µF

C2

1µF

L3

1µF

4.7µF

1µF

2.2µF

+15V

–15V

+5V

ADR434

REFx

PD

AGND DGND

AD8031

4.096V

+

–

1.78Ω

DNI

50kΩ

L1

47µH

L2

47µH

+5V

+5V

BUF

PGIA

PulSAR

ADC

TRACK

AND

HOLD

INx OR COM

VSSH

AGND

VDDH

PGIA

TRACK

AND

HOLD

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