SimCom SIM5300E Hardware Design page 23

577uS
I
VBAT
VBAT
Figure 6: Reference circuit of the DC-DC power supply
Using large tantalum capacitors (above 100uF) is the best way to reduce the voltage drops. For better RF
performance and system stability, some multi-layer ceramic chip (MLCC) capacitors (0.1/1uF) need to be used for
EMC, which have low ESR in high frequencies. Adding 33pF capacitors can effectively eliminate high frequency
interference. Note that capacitors should be put close to VBAT pins. Also, users should minimize the PCB trace
impedance from the power supply to VBAT pins by widening trace to 80 mils or more. It is suggested to use a
zener diode, and its reverse zener voltage is 5.1V and dissipation power is more than 500mW.The following figure
is the recommended circuit.
Table 6: Recommended zener diode models
No. Manufacturer
1 On semi
2 Prisemi
3 Vishay
4 Crownpo
SIM5300E_Hardware_Design_V1.02
4.615mS
VBAT
100uF100nF 33pF
Figure 7: VBAT input application circuit
Part Number Power
MMSZ5231BT1G 500mW
PZ3D4V2H 500mW
MMSZ4689-V 500mW
CDZ55C5V1SM 500mW
5.1V
500mW
Package
SOD123
SOD323
SOD123
0805
Burst:2A
Max:300mV
15