ADA4431-1

Rev. 0 | Page 10 of 12

EVALUATION BOARD

The ADA4431-1 evaluation board allows designers to assess

the performance of the part in their particular application. The

board includes input and output SMA coaxial connectors and

75 Ω-controlled impedance signal traces. Power (2.5 V to 3.6 V)

is applied to the red V+ loop connector, and ground is connected

to the black GND loop connector.

The output signal can be configured for dc coupling or ac

coupling. When ac-coupled, two options are available: the

standard single capacitor configuration (minimum of 220 μF)

and the SAG-corrected configuration, using two smaller

capacitors (47 μF and 22 μF).

Jumper Block J2 allows the load detect feature to be evaluated

without connecting an external video load. Connecting a

jumper from the center pin to the 75 position applies a 75 Ω

load to the output and causes the LDO pin to go high.

Connecting the center pin to the GND position short circuits

the output, causing the ADA4431-1 to power down, and the

LDO pin to go low. If an external video load is connected to

the OUT connector, the jumper should be removed. With the

jumper removed, disconnecting the external load also causes

the ADA4431-1 to power down.

Jumper Block J4 exercises the disable pin (DIS). When a jumper

is connected from the center pin to V+, the charge pump is

enabled. Connecting the center pin to GND forces the ADA4431-1

into low power mode. With the jumper removed, the ADA4431-1

is enabled but the charge pump is disabled.

A schematic of the ADA4431-1 evaluation board, with output

coupling options, is shown in Figure 17. Figure 18 and Figure 19

show the front and back layout of the evaluation board.

GND

SUBS

1

2

3

4

CAP1

DIS

12

10

9

11

IN

LDO

7

8

6

5

13

14

15

16

ADA4431-1

C1

0.1µF

C2

0.1µF

C7

0.1µF

C3

1.0µF

SUBS

V+

V+

R4

DNI

R3

DNI

LDOUT

LDO

GND

DIS

V+

+

C8

10µF

R2

75Ω

IN

DIS

R1

0Ω

V+

C9

0.1µF

C4

0Ω

C5

0Ω

C6

0Ω

DC-COUPLED

OUTPUT

LD2

R5

75Ω

75Ω

GND

J4

OUT

R6

75Ω

J2

GND

13

14

AC-COUPLED

OUTPUT

C4

0Ω

C5

0Ω

C6

220µF

OUTPUT OPTION 1

13

14

AC-COUPLED OUTPUT

WITH SAG CORRECTION

C4

22µF

C5

47µF

C6

0Ω

OUTPUT OPTION 2

Figure 17. Evaluation Board Schematic