MeiG_SLM320_Hardware Design Manual
MeiG Smart Technology Co., Ltd
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3.4.1 Power Supply
SLM320 module is powered through VBAT pin. The power supply recommended reference design is
shown in Figure 3
Module
VBAT_RF
VBAT_BB
C2
C3
C4
C5
C6
C8
C7
C1
D1
TVS
+
+
100uF
100uF
VBAT
100nF
33pF
10pF
100nF 33pF
10pF
Figure 3 Module power supply circuit
3.4.2 Reduce voltage drop
SLM320 power supply range is from 3.2 V to 4.5 V, during data transmission or voice call, the ripple
current up to 2A typically, due to GSM/GPRS emission burst (every 4.615ms), it may cause voltage drop.
So the power supply for these pads must be able to provide sufficient current up to more than 2A.
User
needs to make sure that the input voltage will never drop below 3.3V.
Figure 4 shows the voltage drop during burst transmission under 2G network
.
VBAT
Min.3.3V
Drop
Ripple
Figure 4 Burst transmission power requirements
To reduce voltage drop, a 100uF filter capacitor with low ESR is required. MLCC has the best ESR. It is
recommended to add 3 ceramic capacitors (100nF, 33pF, 10pF) to VBAT_BB and VBAT_RF pins, and
the capacitors should be placed close to VBAT pins. At the same time, in order to ensure better power
supply performance, a TVS tube is added near the input end of the module VBAT to improve the
module's electrostatic bearing capacity. When the external power supply is connected to the module,
VBAT_BB and VBAT_RF need to adopt star wiring. VBAT_BB wire width shall not be less than 1mm,
and VBAT_RF wire width shall not be less than 2mm. In principle, the longer the line in VBAT, the wider
