Q2686 Wavecom, Q2686 Datasheet - Page 22

• Manufacturer Part Number: Q2686
• Description: Wireless CPU
• Manufacturer: Wavecom

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3.2 Power Supply
3.2.1 Power Supply Description
The power supply is one of the key issues in the design of a GSM terminal.
Due to the burst emission mode used in GSM/GPRS, the power supply must be
able to deliver high current peaks in a short time. During the peaks, the ripple
(U
supply voltage “Power Supply Voltage”).
Only the VBATT power supply input is necessary to provide the Q2686
Wireless CPU
VBATT:
The Q2686 Wireless CPU
be connected to the motherboard through a complete layer on the PCB.
This document is the sole and exclusive property of WAVECOM. Not to be distributed or divulged without
prior written agreement.
WM_PRJ_Q2686_PTS_001-007
VBATT
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) on the supply voltage must not exceed a certain limit (see Table 1 Power
In communication mode, a GSM/GPRS class 2 terminal emits 577μs
radio bursts every 4.615ms (see Figure 2).
In communication mode, a GPRS class 10 terminal emits 1154μs radio
bursts every 4.615ms.
Directly supplies the RF components with 3.6 V. It is essential to keep a
minimum voltage ripple at this connection in order to avoid any phase
error.
The RF Power Amplifier current (1.5 A peak in GSM /GPRS mode) flows
with a ratio of:
Is internally used to provide, via several regulators, the VCC_2V8 and
VCC_1V8 power supply required for the baseband signals.
T
o
o
The rising time is around 10μs.
t = 577 μs
1/8 of the time (around 577μs every 4.615ms for GSM /GPRS cl. 2)
and
2/8 of the time (around 1154μs every 4.615ms for GSM /GPRS
cl. 10).
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.
Figure 2: Power supply during burst emission
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shielding case is the grounding. The ground must
T = 4,615 ms
Q2686 Wireless CPU
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March 6, 2007
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