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to 2A. If the power voltage drops below 3.3V, the module may be shut down automatically. Using a large
tantalum capacitor (above 100uF) will be the best way to reduce the voltage drops. If the power current
cannot support up to more than 2A, users must introduce larger capacitor (typical 1000uF) to storage
electric power, especially GPRS multiple time slots emission.
For the consideration of RF performance and system stability, another large capacitor (above 100uF)
should be located at the VBAT pin and some multi-layer ceramic chip (MLCC) capacitors (0.1uF) need to
be used for EMC because of their low ESR in high frequencies. Note that capacitors should be put beside
VBAT pins as close as possible. Also User should minimize the PCB trace impedance from the power
supply to the VBAT pins through widening the trace to 80 mil or more on the board.
There are three sections about how to design and optimize users’ power systems.
Power supply circuit
We recommend DCDC or LDO is used for the power supply of the module, make sure that the peak
current of power components can rise up to more than 2A. The following figure is the reference design of
+5V input power supply. The designed output for the power supply is 4.1V, here a linear regulator can be
used.
Vin
Vout
ON/
OFF
GND
FB
3
+
PWR_CTRL
R102
R101
FB101
VBAT
100K
43K
270 OHM
+
C103
330uF
C104
100nF
U101 MIC29302
5
4
1
2
C101
C102
100uF
1uF
DC INPUT
Figure 10: Reference circuit of the LDO power supply
If there is a big difference between the input voltage and the desired output (VBAT), a switching converter
power will be preferable because of its better efficiency, especially at the high current situation. The
following figure is the reference circuit. Note that DCDC may deprave RF performance because of ripple
current intrinsically.
SIM5320J-TE_Hardware Design_V1.01
2012-11-09
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