Hardware+Design V1.07

Smart Machine Smart Decision
Figure 10: Reference circuit of the LDO power supply
If there is a big difference between the input voltage and the desired output (VBAT), a switching converter
power will be preferable because of its better efficiency, especially at the high current situation. The
following figure is the reference circuit. Note that DCDC may deprave RF performance because of ripple
current intrinsically.
Figure 11: Reference circuit of the DCDC power supply
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_BB 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.
Note: Under-voltage warning function is disabled by default, user can enable it by the AT command “AT+CVALARM”.
Auto power off feature is disabled by default, user should set it by the AT command “AT+CPMVT” to an appropriate
value. Please refer to Document [1].
SIM5320_Hardware Design_V1.07 2012-09-21
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