Power Supply Sequencing; Power Up Sequence; Power Down Sequence; Figure 150: Recommended Power Up Sequence - Analog Devices ADV7850 Hardware Manual

Some graphic controllers use substantially different levels of power when active (during active picture time) and when idle (during
horizontal and vertical synchronization periods). This can result in a measurable change in the voltage supplied to the analog supply
regulator, which can in turn produce changes in the regulated analog supply voltage. This can be mitigated by regulating the analog
supply, or at least PVDD, from a separate, cleaner, power source.
It is also recommended to use a single ground plane for the entire board. Repeatedly, experience has shown that the noise performance is
the same or better with a single ground plane. Using multiple ground planes can be detrimental because each separate ground plane is
smaller and long ground loops can result.
In some cases, using separate ground planes is unavoidable. For those cases, it is recommended to place, at least, a single ground plane
under the ADV7850.It is important to place components wisely because the current loops are much longer when using split ground planes
as the current takes the path of least resistance.
Example of a current loop:
Power plane => ADV7850 => digital output trace => digital data receiver => digital ground plane => analog ground plane.

Power Supply Sequencing

16.3.1

16.3.1.1 Power Up Sequence

The recommended power up sequence of the ADV7850 is as follows:
•
3.3 V supplies
• 1.8 V supplies
Notes:
•
Reset should be held low while the supplies are being powered up
• 3.3 V supplies should be powered up first
•
1.8 V supplies should be powered up after 3.3 V supplies are established
Alternatively, the ADV7850 may be powered up by asserting all voltage supplies simultaneously.
Note: In this case, care must be taken to ensure that a lower rated supply does not go above a higher rated supply level, as the supplies are being
established.

16.3.1.2 Power Down Sequence

The ADV7850 supplies may be de-asserted simultaneously as long as a higher rated supply does not go below a lower rated supply.
Rev. A May 2012
3 .3 V
1 .8 V
3 .3 V S U P P L IE S
P O W E R -U P

Figure 150: Recommended Power Up Sequence

430
3 .3 V S U P P L IE S
1 .8 V S U P P L IE S
1 .8 V S U P P L IE S
P O W E R -U P
ADV7850