Smart Machine Smart Decision
SIM800C_Hardware_Design_V1.02
17
2015-4-27
4.
Application Interface
4.1.
Power Supply
The power supply range of SIM800C is from 3.4V to 4.4V. Recommended voltage is 4.0V. The transmitting
burst will cause voltage drop and the power supply must be able to provide sufficient current up to 2A. For the
VBAT input, a bypass capacitor (low ESR) such as a 100 µF is strongly recommended.
For the VBAT input, a 100uF Tantalum capacitor (C
A
low ESR) and a 1uF~10uF Ceramics capacitor C
B
are
strongly recommended. Increase the 33pF and 10pF capacitors can effectively eliminate the high frequency
interference. A 5.1V/500mW Zener diode is strongly recommended, the diode can prevent chip from damaging
by the voltage surge. These capacitors and Zener diode should be placed as close as possible to SIM800C
VBAT pins.
V B A T
5.1V
500m W
C
A
C
B
33pF 10pF
Figure 5: Reference circuit of the VBAT input
Table 6: Recommended zener diode
Vendor
Part number
Power(watts)
Packages
1
On semi
MMSZ5231BT1G
500mW
SOD123
2
Prisemi
PZ3D4V2H
500mW
SOD323
3
Vishay
MMSZ4689-V
500mW
SOD123
4
Crownpo
CDZ55C5V1SM
500mW
0805
The following figure is the reference design of +5V input power supply. The output power supply is 4.1V, thus a
linear regulator can be used.
V in
V out
GN
D
F B
3
+
P W R _C T R L
R 102
R 101
V B A T
100K
43K
+
C 103
330uF
C 104
100nF
U 101 M IC 29302
5
4
1
2
C 101
C 102
100uF
1uF
D C IN P U T
R 103
470Ω
O n/O ff
Figure 6: Reference circuit of the LDO power supply
If there is a high drop-out between the input and the desired output (VBAT), a DC-DC power supply will be
preferable because of its better efficiency especially with the 2A peak current in burst mode of the module. The
