AD9201

–12–

REV. D

COMMON-MODE LEVEL – V

–30

–35

–80

–0.5

1.5

0

0.5

1.0

–50

–65

–70

–75

–40

–45

–60

–55

1V SPAN

2V SPAN

a. Differential Input, 3 V Supplies

COMMON-MODE LEVEL – V

–30

–35

–80

–0.5

2.5

0

0.5

1.0

–50

–65

–70

–75

–40

–45

–60

–55

1.5

2.0

1V SPAN

2V SPAN

b. Differential Input, 5 V Supplies

COMMON-MODE LEVEL – V

–10

–80

–0.5

0

0.5

1.0

–40

–60

–70

–20

–30

–50

1.5

1V SPAN

2V SPAN

c. Single-Ended Input, 3 V Supplies

COMMON-MODE LEVEL – V

–10

–80

–0.5

2.5

0

0.5

1.0

–40

–60

–70

–20

–30

–50

1.5

2.0

1V SPAN

2V SPAN

d. Single-Ended Input, 5 V Supplies

Figure 29. THD vs. CML Input Span and Power Supply (Analog Input = 1 MHz)

COMMON-MODE PERFORMANCE

Attention to the common-mode point of the analog input volt-

age can improve the performance of the AD9201. Figure 29

illustrates THD as a function of common-mode voltage (center

point of the analog input span) and power supply.

Inspection of the curves will yield the following conclusions:

1. An AD9201 running with AVDD = 5 V is the easiest to

drive.

2. Differential inputs are the most insensitive to common-mode

voltage.

3. An AD9201 powered by AVDD = 3 V and a single ended

input, should have a 1 V span with a common-mode voltage

of 0.75 V.