Technical information

Chapter 2: Hardware Interface Description
December 15, 2009 G30 - Module Hardware Description 13
Figure 2-2 illustrates the power supply behavior during GSM transmission.
Figure 2-2: Transmission Power Drops
Note: 1 TX slot is shown.
It is recommended that the voltage drops during a transmit burst will not exceed 300mV,
measured on the G30 interface connector. In any case, the G30 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, it is recommended to follow
these guidelines:
• Use a 1000 uF, or greater, low ESR capacitor on the G30 supply inputs. The capacitor should
be located as near to the G30 interface connector as possible.
• Use low impedance power source, cabling and board routing.
• Use cabling and routing as short as possible.
• Filter the G30 supply lines using filtering capacitors, as described in Table 2-3.
Table 2-3:
Recommended Power Supply Filtering
Capacitor Usage Description
1000 uF GSM Transmit current
serge
Minimizes power supply
losses during transmit
bursts.
Use maximum possible
value.
10 nF, 100 nF Digital switching noise
Filters digital logic noises
from clocks and data sources.
8.2 pF, 10 pF 1800/1900 MHz GSM
bands
Filters transmission EMI.
33 pF, 39 pF 850/900 MHz GSM
bands
Filters transmission EMI.