AD8139

Rev. A | Page 23 of 24

Exposed Paddle (EP)

Since this is a single-ended-to-differential application on a

single supply, the input common-mode voltage swing must be

calculated to be 0.53 V p-p swinging about a baseline of 1.25 V,

and the minimum negative excursion is approximately 1 V.

The SOIC-8 and LFCSP packages have an exposed paddle on

the underside of its body. In order to achieve the specified

thermal resistance, it must have a good thermal connection to one

of the PCB planes. The exposed paddle must be soldered to a pad

on top of the board that is connected to an inner plane with several

thermal vias.

AD8139

+

–

8

2

1

6

3

4

2.4V

2V p-p

61.9

Ω

5

200

Ω

226

Ω

205

Ω

205

Ω

25

Ω

25

Ω

0.01

µF

0.01

µF

0.01

µF

AIN

AIN

GND C1

0.1

µF

C2

VREF

0.1

µF

5V

3.3V

AD6645

SIGNAL

SOURCE

50

Ω

Figure 62. AD8139 Driving AD6645, 14-Bit, 80 MSPS/105 MSPS A/D Converter