adv7718 Analog Devices, Inc., adv7718 Datasheet - Page 37

• Manufacturer Part Number: adv7718
• Description: Integrated Digital Ccir-601 Pal/ntsc Video Encoder
• Manufacturer: Analog Devices, Inc.

For external buffering of the ADV7177/ADV7178 DAC outputs,
the configuration in Figure 58 is recommended. This configuration
shows the DAC outputs running at half (18 mA) their full current
(34.7 mA) capability. This will allow the ADV7177/ADV7178 to
dissipate less power, the analog current is reduced by 50% with a
R
for 3.3 volt operation as optimum performance is obtained from
the DAC outputs at 18 mA with a V
also adds extra isolation on the video outputs, see buffer circuit
SET
300
PIXEL
PORT
of 300 Ω and a R
R
SET
V
DIGITAL
REF
CORE
ADV7177/ADV7178
V
AA
LOAD
of 75 Ω. This mode is recommended
DAC A
DAC B
DAC C
AA
of 3.3 volts. This buffer
OUTPUT
BUFFER
OUTPUT
BUFFER
OUTPUT
BUFFER
OPTIONAL DAC BUFFERING
75
75
75
APPENDIX 6
in Figure 59. When calculating absolute output full current and
voltage, use the following equation:
FILTER O/P
OPTIONAL
INPUT/
V
I
K = 4.2146 constant , V
OUT
OUT
=
= I
(
V
OUT
REF
R
SET
4
3
× R
× K
AD8051
V
V
CC
CC
LOAD
ADV7177/ADV7178
5
2
)
+
–
1
REF
= 1.235 V
OUTPUT TO
TV MONITOR