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MeiG Smart product technical information
SLM500 Hardware Design Guide Page 49
4.10.1. Charging Detection
When the VBUS pin voltage is higher than 4.0V, a hardware interrupt will be generated
inside the module. The software determines whether the charger is inserted or the USB data
cable is inserted by judging the status of USB_DP/USB_DM.
4.10.2. Charge Control
The SLM500 module can charge the over-discharged battery. The charging process includes
trickle charge, pre-charge, constant current, and constant-voltage charge. When the VBAT
voltage is lower than 3.4V, the module is pre-charged; when VBAT is between 3.4V and 4.2V,
it is charged by the constant current plus constant voltage method optimized for the lithium
battery. At present, the software's charge cut-off voltage is 4.2V, and the back-off voltage is
4.05V.
4.10.3. BAT_CON_TEM
The SLM500 module has battery temperature detection and can be implemented by
BAT_THERM (134 PIN). This requires the internal integration of a 47KΩ thermistor
(negative temperature coefficient) inside the battery to connect the thermistor to the
BAT_THERM pin. During the charging process, the software reads the voltage of the
BAT_THERM pin to determine if the battery temperature is too high. If the temperature is too
high or too low, the battery will stop charging immediately to prevent battery damage. The
battery charging connection diagram is shown below:
Figure 4.29: Charging circuit connection diagram
4.11 UIM Card Interface
The SLM500 can support two SIM cards at the same time to achieve dual card dual standby.
Support SIM card hot swap, can automatically recognize 1.8V and 3.0V cards. The figure
PM215