Specifications

WM_PRJ_Q2400_PTS_001 - 003
6th November 2002
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2.2 Power supply
2.2.1 Power supply description
The power supply is one of the key issues in the design of a GSM terminal.
Due to the burst mission in GSM / GPRS, the power supply must be able to
deliver high current peaks in a short time. During these peaks the ripple (U
ripp
)
and the drop (U
drop
) on the supply voltage must not exceed a certain limit.
In transmission mode, a GSM/GPRS class 2 terminal emits (1Tx) 577µs radio
bursts every 4.615ms.
Uripp
Udrop
Uripp
Udrop
T = 4,615 ms
t = 577 µs
Two different inputs are provided for the power supply. The first one, VBATT is
used to supply the RF part and VDD, the second one is used to supply the
baseband part.
Note
:
•
It is possible to connect VBATT to VDD.
•
In case of separate power supplies, they have to be in the same state (ie.
both active or inactive at the same time).
VBATT: supplies directly the RF components with 3.6 V. It is essential to
minimize the voltage ripple at this connection in order to avoid any phase error.
The RF Power Amplifier current (2.0A peak in GSM /GPRS mode) flows with a
ratio of 1/8 of the time, around 577µs every 4.615ms for GSM /GPRS cl 2. The
rising time is around 10µs.
VDD: supplies the +2.8V ballast regulators of the WISMO Quik Q2403 Series. It
is essential to keep the voltage over 3.1 volts.
The WISMO Quik Q2403 Series shielding case is the grounding. The ground
has to be connected on the mother board through a complete layer on the PCB.