DM505LRBABF datasheet(282/295 Pages) TI2

282 / 295 page

LOAD

cvideo_vfb

Reconstruction

Filter

~9.5 MHz

(A)

Amplifier

3.7 V/V

(B)

75 W

OUT

cvideo_tvout

cvideo_vfb

Reconstruction

Filter

~9.5 MHz

(A)

(B)

282

DM505

SPRS976E – NOVEMBER 2016 – REVISED MAY 2018

www.ti.com

Submit Documentation Feedback

Applications, Implementation, and Layout

7.10 CVIDEO/SD-DAC Guidelines and Electrical Data/Timing

The device's analog video CVIDEO/SD-DAC TV analog composite output can be operate in one of two

modes: Normal mode and TVOUT Bypass mode. In Normal mode, the device’s internal video amplifier is

used. In TVOUT Bypass mode, the internal video amplifier is bypassed and an external amplifier is

required.

Figure 7-72 shows a typical circuit that permits connecting the analog video output from the device to

standard 75-Ω impedance video systems in Normal mode.

Reconstruction Filter (optional)

AC coupling capacitor (optional)

Figure 7-72. TV Output (Normal Mode)

Figure 7-73 shows a typical circuit that permits connecting the analog video output from the device to

standard 75-Ω impedance video systems in TVOUT Bypass mode.

Reconstruction Filter (optional). Note: An amplifier with an integrated reconstruction filter can alternatively be used

instead of a discrete reconstruction filter.

AC coupling capacitor (optional)

Figure 7-73. TV Output (TVOUT Bypass Mode)

During board design, the onboard traces and parasitics must be matched for the channel. The video DAC

output pins (cvideo_tvout / cvideo_vfb) are very high-frequency analog signals and must be routed with

extreme care. As a result, the paths of these signals must be as short as possible, and as isolated as

possible from other interfering signals. In TVOUT Bypass mode, the load resistor and amplifier/buffer

should be placed as close as possible to the cvideo_vfb pin. Other layout guidelines include:

•

Take special care to bypass the vdda_dac power supply pin with a capacitor.

•

In TVOUT Bypass mode, place the RLOAD resistor as close as possible to the Reconstruction Filter

and Amplifier. In addition, place the 75-Ω resistor as close as possible (< 0.5 inch) to the

Amplifier/buffer output pin. To maintain a high-quality video signal, the onboard traces after the 75-Ω

resistor should have a characteristic impedance of 75 Ω (± 20%).

•

In Normal mode,cvideo_vfb is the most sensitive pin in the TV out system. The ROUT resistor should

be placed as close as possible to the device pins. To maintain a high-quality video signal, the onboard

traces leading to the cvideo_tvout pin should have a characteristic impedance of 75 Ω (± 20%) starting

from the closest possible place to the device pin output.

•

Minimize input trace lengths to the device to reduce parasitic capacitance.

•

Include solid ground return paths.

•

Match trace lengths as close as possible within a video format group.

DM505LRBABF Datasheet(PDF) 282 Page - Texas Instruments

DM505LRBABF Datasheet(HTML) 282 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL