MTH Inc. MGM-312E Manuel D’Utilisation
GSM/GPRS/EDGE Module(MGM-312E)
Preliminary
Hardware Design
Copyright © by MTH. All rights reserved.
Design Document
Rev 008 – 14 Mars 200611
Page 8 of 34
3.2 Power
Supply
The power supply is one of the key issues in the design of a GSM terminal.
Due to the bursted emission in GSM/GPRS, the power supply must be able to on the supply voltage
must not exceed a certain limit.
In communication mode, a GSM/GPRS terminal transmits 577us (1TX) or 1154us (2TX) radio bursts
every 4.615ms, as described in the diagram hereunder.
Due to the bursted emission in GSM/GPRS, the power supply must be able to on the supply voltage
must not exceed a certain limit.
In communication mode, a GSM/GPRS terminal transmits 577us (1TX) or 1154us (2TX) radio bursts
every 4.615ms, as described in the diagram hereunder.
Figure 3 Waveform of the max drop and ripple authorized for VBATT
The power supply voltage features given in the table hereafter will guarantee the nominal operation of
the module
the module
V
min
V
nom
V
max
Condition
VBATT 3.3V*
3.6V
4.8V
U
ripple ≤ 50mVpp for f < 200kHz
U
ripple
≤ 2mVpp for f>200kHz
(*): This value has to be guaranteed during the burst (with 2.0A peak in GSM mode)
The transmitting burst will cause voltage drop and the power supply must be able to provide sufficient
current up to 2A. For the VBAT input, a bypass capacitor (low ESR) such as a 100uF is strongly
recommended; this capacitor should be placed as close as possible to MGM-312E VBAT pins.
There are 3 ways of supplying power to MGM-312E.
The transmitting burst will cause voltage drop and the power supply must be able to provide sufficient
current up to 2A. For the VBAT input, a bypass capacitor (low ESR) such as a 100uF is strongly
recommended; this capacitor should be placed as close as possible to MGM-312E VBAT pins.
There are 3 ways of supplying power to MGM-312E.
9
To connect battery directly.
9
To use linear regulator.
9
To use DC-DC converter.
For low voltage drop of VBAT, it’s suggested to connect battery directly or use DC-DC convertor. The
PCB traces from the VBAT pins to the power supply must be wide enough (at least 60mil) to decrease
voltage drops in the transmit burst. The power IC and the bypass capacitor should be placed to the
module as close as possible.
PCB traces from the VBAT pins to the power supply must be wide enough (at least 60mil) to decrease
voltage drops in the transmit burst. The power IC and the bypass capacitor should be placed to the
module as close as possible.