AD6674 datasheet(34/97 Pages) AD

34 / 97 page

Data Sheet

AD6674

Rev. C | Page 33 of 96

Absolute Maximum Input Swing

The absolute maximum input swing allowed at the inputs of the

AD6674 is 4.3 V p-p differential. Signals operating near or at

this level can cause permanent damage to the ADC.

VOLTAGE REFERENCE

A stable and accurate 1.0 V voltage reference is built into the

AD6674. This internal 1.0 V reference sets the full-scale input

range of the ADC. The full-scale input range can be adjusted via

swing, see Table 45. Figure 87 shows the block diagram of the

internal 1.0 V reference controls.

ADC

CORE

FULL-SCALE

VOLTAGE

ADJUST

V_1P0 PIN

CONTROL SPI

(0x025 AND

0x024)

V_1P0

VIN–A/

VIN–B

VIN+A/

VIN+B

INTERNAL

V_1P0

GENERATOR

INPUT FULL-SCALE

RANGE ADJUST

SPI REGISTER

(0x025 AND 0x024)

Figure 87. Internal Reference Configuration and Controls

reference or to provide an external 1.0 V reference. When using

an external voltage reference, provide a 1.0 V reference. The

full-scale adjustment is made using the SPI, irrespective of the

reference voltage. For more information on adjusting the full-

scale level of the AD6674, refer to the Memory Map Register

Table section.

The use of an external reference may be necessary, in some

applications, to enhance the gain accuracy of the ADC or

improve thermal drift characteristics. Figure 88 shows the

typical drift characteristics of the internal 1.0 V reference.

–50

TEMPERATURE (°C)

0.9998

0.9999

1.0000

1.0001

1.0002

1.0003

1.0004

1.0005

1.0006

1.0007

1.0008

1.0009

1.0010

Figure 88. Typical V_1P0 Drift

The external reference must be a stable 1.0 V reference. The

ADR130 is a good option for providing the 1.0 V reference.

Figure 89 shows how the ADR130 can be used to provide the

external 1.0 V reference to the AD6674. The grayed out areas

show unused blocks within the AD6674 while the ADR130

provides the external reference.

FULL-SCALE

VOLTAGE

ADJUST

V_1P0

0.1µF

VOUT 4

SET 5

NC 6

VIN

GND

ADR130

0.1µF

INPUT

FULL-SCALE

CONTROL

INTERNAL

V_1P0

GENERATOR

Figure 89. External Reference Using the ADR130

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