GE864-QUAD V2 Hardware User Guide
1vv0300841 Rev.5
–
2017-05-11
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights
Reserved.
Page 34 of 77
This generated heat will be mostly conducted to the ground
plane under the GE864-QUAD V2 ; you must ensure that your
application can dissipate it.
6.3.3.
Power Supply PCB Layout Guidelines
As seen on the electrical design guidelines the power supply
shall have a low ESR capacitor on the output to cut the
current peaks and a protection diode on the input to protect
the supply from spikes and polarity inversion. The placement
of these components is crucial for the correct working of the
circuitry. A misplaced component can be useless or can even
decrease the power supply performances.
The Bypass low ESR capacitor must be placed close to the
Telit GE864-QUAD V2 power input pads or in the case the power
supply is a switching type it can be placed close to the
inductor to cut the ripple provided the PCB trace from the
capacitor to the GE864-QUAD V2 is wide enough to ensure a
dropless connection even during the 2A current peaks.
The protection diode must be placed close to the input
connector where the power source is drained.
The PCB traces from the input connector to the power
regulator IC must be wide enough to ensure no voltage drops
occur when the 2A current peaks are absorbed. Note that this
is not made in order to save power loss but especially to
avoid the voltage drops on the power line at the current
peaks frequency of 216 Hz that will reflect on all the
components connected to that supply, introducing the noise
floor at the burst base frequency. For this reason while a
voltage drop of 300-400 mV may be acceptable from the power
loss point of view, the same voltage drop may not be
acceptable from the noise point of view. If your application
does not have audio interface but only uses the data feature
of the Telit GE864-QUAD V2 then this noise is not so
disturbing and power supply layout design can be more
forgiving.
The PCB traces to the GE864-QUAD V2 and the Bypass capacitor
must be wide enough to ensure no significant voltage drops
occur when the 2A current peaks are absorbed. This is for the
same reason as previous point. Try to keep this trace as
short as possible.
The PCB traces connecting the Switching output to the
inductor and the switching diode must be kept as short as
possible by placing the inductor and the diode very close to
the power switching IC (only for switching power supply).
