AD8148(Rev0) Просмотр технического описания (PDF) - Analog Devices

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Компоненты Описание

производитель

AD8148
(Rev.:Rev0)

Triple Differential Driver for Wideband Video

Analog Devices 

AD8146/AD8147/AD8148

Figure 39 illustrates the frequency response of the pre-emphasis

network.

Figure 40 illustrates the frequency response of the pre-emphasis

circuit cascaded with the cable compared with that of the cable

alone. It can be seen that the overall response is flat to within

±0.4 dB. The ±0.4 dB ripple in the response is due to the fact

that the pre-emphasis network is linear, comprised of two real-

axis pole/zero pairs, and the cable response is nonlinear.

EXPOSED PADDLE (EP)

The 24-lead LFCSP has an exposed paddle on the underside of

its body. To achieve the specified thermal resistance, it must

have a good thermal connection to one of the PCB planes. The

exposed paddle must therefore be soldered to a pad on the top

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

thermal vias. The AD8147/AD8148 use the paddle as a ground

reference; therefore, for these parts, the PCB plane used must be

the ground plane.

75Ω

VIDEO

SOURCE

18pF

487Ω

30pF

442Ω

82.5Ω

442Ω

487Ω

30pF

18pF

39.2Ω

500Ω

500Ω

2kΩ

+

AD8148

–

2kΩ

49.9Ω

49.9Ω

Figure 38. Pre-Emphasis Network Using the AD8148 for 30 Meters of UTP Cable

100 FEET

100Ω

UTP

12

VS = ±5V

11

10

9

8

7

6

0.1

1

10

100

FREQUENCY (MHz)

Figure 39. AD8148 Pre-Emphasis Network Frequency Response

9

VS = ±5V

6

3

PRE-EMPHASIS

NETWORK

WITH CABLE

0

–3

CABLE ALONE

–6

–9

0.1

1

10

100

FREQUENCY (MHz)

Figure 40. AD8148 Pre-Emphasis Network Cascaded With

30 Meters of UTP Cable vs. UTP Cable Alone

Rev. 0 | Page 21 of 24

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