User's Manual

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User Manual 2012/06/28
Figure 9: PCM interface timing
3.4 POWER SUPPLY
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module can be supplied by a battery or by any DC/DC converter compliant with the input voltage range
from 3.3V to 4.5V and 2A current capability.
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> VBAT traces are required to be as short and as wide as possible.
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VBAT ceramic decoupling capacitors of at least 100µF/10V are required to ensure good RF performance.
It is strongly recommended to place capacitors close to the module’s connection pad and connected via low
resistance tracks to VBAT and GND.
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PCB tracks must be well dimensioned to support 2 A maximum current (Burst current 1.8A plus the extra
current for the other used I/Os). The voltage ripple caused by serial resistance of power supply path
(Battery internal resistance, tracks and contact resistance) could result in the voltage drops.
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To prevent any issue in the power up procedure, the typical rise time for VBAT should be around 1ms.
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module does not manage the battery charging.
3.4.1 Burst conditions
Communication mode (worst case: 2 continuous GSM time-slot pulses):
Figure 10: GSM/GPRS Burst Current rush
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A 47µF with Low ESR capacitor is highly recommended for VBAT and close to the module pins 43/44.