23
23
mosaic-X5 Integration
23
4.2
Electrical Recommendations
•
All ground pins must be connected.
•
Do not drive a non-
zero voltage into input pins (pins type “I” in the tables
in chapter
3) when the module is not powered (i.e. when there is no supply on the VDD_3V3
pins).
•
When pull-up/down resistors are needed, use 10 k
.
•
Unused pins (e.g. pins of an unused interface) must be left unconnected unless
explicitly mentioned otherwise.
•
Many pins are reserved, which means that their functionality is proprietary or is
not supported yet by the firmware. Reserved pins are marked “Reserved_NC” and
“Reserved_GND”. The Reserved_NC pins
must be left unconnected. The
Reserved_GND pins (i.e. only V23 and AB7) must be tied to ground.
4.3
Decoupling
The VDD_3V3 supply shall be decoupled with at least a 22 µF capacitor with proper voltage
rating. The other supply terminals don’t need
external decoupling.
4.4
Layout Recommendations
4.4.1
Coplanarity
It is important to avoid warpage of the motherboard on which the module will be
soldered. More in particular:
•
Use a symmetrical layer stack
•
Make sure layers opposite from the center of the board have a similar amount of
copper (copper-balancing).
•
Avoid iron-based soldered shielding cans in the proximity of mosaic-x5
•
If the motherboard thickness is 1.2 mm or less, it needs to be supported during
reflow.
4.4.2
Power
The power trace to the VDD_3V3 terminals should be sufficiently wide to avoid excessive
voltage drop. Online trace resistance calculators are avaible for this, e.g. at
https://www.eeweb.com/tools/trace-resistance
. The resistance of the trace to the power
supply shall be less than (<minimum supply voltage> - 3.135V)/0.5A.
Use a ground plane.
