G510 Hardware User Manual Page
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Special care must be taken when designing the power supply of the module. The single external DC
power source indirectly supplies all the digital and analog interfaces, but also directly supplies the RF
power amplifier (PA). Therefore, any degradation in the power supply performance, due to losses, noises
or transients, will directly affect the module performance.
The burst-mode operation of the GSM transmission and reception draws instantaneous current surges
from the power supply, which causes temporary voltage drops of the power supply level. The transmission
bursts consume the most instantaneous current, and therefore cause the largest voltage drop. If the
voltage drops are not minimized, the frequent voltage fluctuations may degrade the module performance.
It is recommended that the voltage drops during a transmit burst will not exceed 300mV, measured on the
module interface connector. In any case, the module supply input must not drop below the minimum
operating level during a transmit burst. Dropping below the minimum operating level may result in a low
voltage detection, which will initiate an automatic power-off.
To minimize the losses and transients on the power supply lines, please follow these guidelines:
Use a 1000 uF, or greater, low ESR capacitor on the module supply inputs. The capacitor should be
located as near to the module interface connector as possible.
Use low impedance power source, cabling and board routing.
Use cabling and routing as short as possible.
Filter the module supply lines using filtering capacitors, as described in the table.
GSM Transmit current
serge
Minimizes power supply losses during
transmit bursts. Use maximum possible
value.
Filters digital logic noises from clocks.
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