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I'm designing a CCD control circuit and have some questions.

1.Should the ground in the 1st and 2nd position in the oval be analog ground or digital ground?

2.If they should be the DGND, whether the AGND and DGND should be connected through a passage or they can be isolated? enter image description here

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  • \$\begingroup\$ whay do you mean by CCD? \$\endgroup\$ – Jasen Aug 12 '18 at 2:09
  • \$\begingroup\$ CCD means charge-coupled device. It is used for the camera. \$\endgroup\$ – Ross Aug 12 '18 at 23:41
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The grounds at the power supply subsystem want to be the digital ground plane. Group all of your analogue components that have the analogue grounds into an island ground area that then connects at one point to the digital ground. Place the filtering ferrite bead component that you isolate the digital power from the analogue power directly over the single point connection between the grounds.

Your picture is somewhat misleading because you just show the ground connections of the filter capacitors. You should also show the ground connections for the DC/DC, LDO, Op-Amp and CCD.

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  • \$\begingroup\$ Thank you for your answer. I've updated the schematic for this question. \$\endgroup\$ – Ross Aug 12 '18 at 23:40
  • \$\begingroup\$ @RossLee - You should have kept the shown capacitors as they show the good intention to provide the filtering that they provide for critical parts of the circuit. \$\endgroup\$ – Michael Karas Aug 13 '18 at 5:36
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Conventional wisdom about this has changed in recent years. It is considered more important that currents (even small digital switching) return physically close from where they came. In theory, you can actually just have one big ground plane and as long as you don't have current loops, it should be fine. Although I must confess I still use separate grounds for digital and analog.

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