Datasheet

Data Sheet ADA4432-1/ADA4433-1
Rev. A | Page 23 of 28
LOW POWER CONSIDERATIONS
Using a series source termination and a shunt load termination on
a low supply voltage with the ADA4432-1 or ADA4433-1 realizes
significant power savings compared with driving a video cable
directly from a DAC output. Figure 56 shows a video DAC
driving a cable directly. Properly terminated, a DAC driven
transmission line requires two 75 Ω loads in parallel, demanding
in excess of 33 mA to reach a full-scale voltage level of 1.3 V.
Figure 57 shows the same video load being driven using the
ADA4432-1 and a series-shunt termination. This requires two
times the output voltage to drive the equivalent of 150 Ω but
only requires a little more than 15 mA to reach a full-scale output.
When running on the same supply voltage as the DAC, this result
in a 74% reduction in power consumption compared with the
circuit in Figure 56. The high order filtering provided by the
ADA4432-1 lowers the requirements on the DAC oversampling
ratio, realizing further power savings. The main source for power
savings realized by the configuration shown in Figure 57 comes
from the low drive mode setting for the ADV7391. This along
with the reduction in the requirement for oversampling (PLL
turned off), and the reduced load current required, results in
significant power savings.
For more detailed information on low drive mode, see the
ADV7391 data sheet.
Figure 56. Driving a Video Transmission Line Directly with a DAC
Figure 57. Driving a Video Transmission Line with the ADA4432-1
75Ω CABLE
75Ω
ADV7391
510Ω
3.3V
R
SET
75Ω
10597-038
300Ω
75Ω
75Ω
75Ω CABLE
ADV7391
4.12kΩ
3.3V
3.3V
R
SET
10597-039
ADA4432-1