User's Manual

USER MANUAL 1.34

STM 300 / STM 300C / STM 300U

4.8 Layout recommendations for foot pattern

The length of lines connected to I/Os should not exceed 5 cm.

It is recommended to have a complete GND layer in the application PCB, at least

in the area below the module and directly connected components (e.g. mid-layer

of your application PCB).

Due to unisolated test points there are live signals accessible on the bottom side

of the module.

Please regard the following advices to prevent interference with your application

circuit:

 Avoid any copper structure in the area directly underneath the module

(top-layer layout of your application PCB). If this is not possible in your de-

sign, please provide coating on top of your PCB to prevent short circuits to

the module test pads. All bare metal surfaces including via have to be cov-

ered (e.g. adequate layout of solder resist).

 It is mandatory that the area marked by the circle in the figure below is

kept clear of any conductive structures in the top layer and 0.3 mm below.

Otherwise RF performance will be degraded!

Furthermore, any distortive signals (e.g. bus signals or power lines) should not be

routed underneath the module. If such signals are present in your design, we sug-

gest separating them by using a ground plane between module and these signal

lines.

The RVDD line should be kept as short as possible. Please consider recommenda-

tions in section 4.4.