Application Interface Specification; Power Supply; Power Supply Pin; Design Guide - SimCom SIM5320AL User Manual

3

Application Interface Specification

3.1

Power Supply

The power supply pins of SIM5320AL include VBAT_RF and VBAT_BB. VBAT_RF directly supplies the
power to RF PA; VBAT_BB supplies the power to the baseband system. For the VBAT_RF, the current
consumption rises typically to peak of more than 2A. So the power supply must be able to provide
sufficient current up to more than 2A. The following figure is the VBAT_RF voltage ripple wave at the
maximum power transmit phase.
Please refer to Figure 8—Application circuit VBAT_RF=4.0V, VBAT maximum output current =2A,
C =100 µF tantalum capacitor (ESR=0.7Ω) and C
A
3.1.1

Power Supply Pin

Two VBAT_RF and two VBAT_BB pins are dedicated to connect the supply voltage.
Table 4: Pin description
Pin type Pin name
VBAT_RF
POWER
VBAT_BB
Note: 1.Though the VBAT_RF and VBAT_BB are supplied by the same voltage level, they are different pins. VBAT_RF
is for RF section and VBAT_BB is for baseband system.
2. When the module is power off, users must pay attention to the issue about current leakage. Refer to Chapter 3.10.2
Note2.
3.1.2

Design Guide

Mostly, user connects the VBAT_RF and VBAT_BB pins with one power supply. Make sure that the input
voltage at the VBAT_BB pin will never drop below 3.3V even during a transmit burst when the current
consumption rises up to more than 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 2A, users must introduce larger capacitor (typical
1000uF) to storage electric power.
For the consideration of RF performance and system stability, another large capacitor (above 100uF)
should be located at the VBAT_RF 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
SIM5320AL_User Manual_V1.01
=1µF.
B
Min Typ
3.3 3.8
3.3 3.8
22
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Max Unit
4.2 V
4.2 V
2014-08-20