ExternalVREFApplied

V

-

75

70

65

60

55

50

45

40

2.05 2.15 2.25 2.35 2.45

3.15

f =400MSPS

f

=70MHz

S

IN

2.55 2.65 2.75 2.85 2.95 3.05

A

= 4dBFS

-

IN

A

= 3dBFS

-

IN

A

= 2dBFS

-

IN

A

= 1dBFS

-

IN

A

= 5dBFS

-

IN

A

= 6dBFS

-

IN

ExternalVREFApplied

V

-

1.0

0.5

0

-0.5

-1.0

-1.5

-3.0

2.2

2.3

2.4

2.5

3.1

2.6

2.7

2.8

f =400MSPS

f

=70MHz

A

=< 1dBFS

S

IN

IN

-

2.9

3.0

BestFit:

y= 3.14x+7.5063

-

-2.0

-2.5

ExternalVREFApplied

V

-

90

80

70

60

50

40

2.05 2.15 2.25 2.35 2.45

3.15

f =400MSPS

f

=70MHz

S

IN

2.55 2.65 2.75 2.85 2.95 3.05

A

= 6dBFS

-

IN

A

= 4dBFS

-

IN

A

= 3dBFS

-

IN

A

= 5dBFS

-

IN

A

= 2dBFS

-

IN

A

= 1dBFS

-

IN

ADS5474

SLAS525C – JULY 2007 – REVISED JANUARY 2016

www.ti.com

Device Functional Modes (continued)

Figure 38. Signal Gain Adjustment vs External Reference

(VREF)

For dc-coupled applications that use the VCM pin of the ADS5474 device as the common mode of the signal in

the analog signal gain path prior to the ADC inputs, the information in Figure 42 is useful to consider versus the

allowable common-mode range of the device that is receiving the VCM voltage, such as an operational amplifier.

Because it is pin-compatible, it is important to note that the ADS5463 does not have a VCM pin and primarily

uses the VREF pin to provide the common-mode voltage in dc-coupled applications. The ADS5463 (VCM = 2.4

V) and ADS5474 (VCM = 3.1V) devices do not have the same common-mode voltage. To create a board layout

that may accommodate both devices in dc-coupled applications, route VCM and VREF both to a common point

that can be selected via a switch, jumper, or a 0-

Ω resistor.

22

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