Recommended Power Supply Circuit; Voltage Monitor - SIM Tech SimCom SIM7100 Hardware Design

3.1.2

Recommended Power supply circuit

We recommend DCDC or LDO is used for the power supply of the module, make sure that the peak
current of power components can rise up to more than 2A. The following figure is the reference design of
+5V input linear regulator power supply. The designed output for the power supply is 3.8V.
DC INPUT
FUSE
If there is a big difference between the input voltage and the desired output (VBAT) or better efficiency is
more important, a switching converter power supply will be preferable. The following figure is the
reference circuit.
Note: DCDC may deprave RF performance because of ripple current intrinsically.
3.1.3

Voltage monitor

To monitor the power supply voltage, user can use the AT command "AT+CBC", this command has two
parameters: the battery status and the voltage value (mV). It will return the capacity percentage and actual
value of battery (at the VBAT pin). The voltage is continuously measured at intervals, whenever the
measured battery voltage is lower than a specific value set by the AT command "AT+CVALARM". For
example, if the voltage value is set to be 3.4V, the following URC will be presented: "warning! voltage is
low: 3.3v".
If the voltage is lower than a specific value which is set by the AT command "AT+CPMVT", the module
will be powered off automatically and AT commands cannot be executed any more.
SIM7100_Hardware Design_V1.01
U101 MIC29302
2
+
1
C101 C102
100uF
1uF
PWR_CTRL
Figure 9: Reference circuit of the LDO power supply
Figure 10: Reference circuit of the DCDC power supply
4
Vout
Vin
5
R101
On/Off
FB
100K
3
R102
47K
27
Smart Machine Smart Decision
VBAT
+
C103 R103
C104
470R
330uF 100nF
2015-01-20