Application information

RHF1401

16/29

External references, common mode:

In applications that require a different full scale magnitude, it is possible to force the VREFP

and VREFM pins from an external voltage reference device. In this configuration, the

RHF1401 has better performance, as illustrated in Figure 15 and Figure 16.

VREFP, VREFM and INCM into high impedance inputs that have to be forced by external

references.

Using the RHF1401 with an external voltage reference device yields optimum performance

when configured as shown in Figure 17.

Figure 17.

External reference setting

Note:

In multi-channel applications, the high impedance input of the references allows you to drive

several ADCs with only one voltage reference device.

The improved dynamic performance is shown in Figure 18 and Figure 19.

Figure 15.

Figure 16.

Distortion vs. REFP(1)

1.

65

68

71

74

77

80

0.8

0.9

1

1.1

1.2

1.3

1.4

REFP (V)

11

11.2

11.4

11.6

11.8

12

12.2

12.4

ENOB

SNR

SINAD

-100

-95

-90

-85

-80

-75

-70

0.8

0.9

1

1.1

1.2

1.3

1.4

REFP (V)

THD

SFDR

1k

Ω

RHF1401

VIN

VINB

VREFM

VREFP

external

reference

VCCA

330pF

4.7µF

10nF

REFMODE

“1”