User's Manual

MeiG hardware design guide
23
4.11 Charging Interface
4.11.1 Charging Detection
The USB_VBUS power supply is a USB power supply or an adapter power supply. It can be used as a
USB plug-in detection and charge the battery through the internal PMU of the module. The power
input voltage range is 4.35~6.3V, and the recommended value is 5V. The module supports single-cell
lithium battery charge management, and different capacity models need to set different charging
parameters. The module's built-in linear charging circuit supports up to 1.44A of charging current.
Figure 4.28: Battery connection diagram
4.11.2 Charge Control
The SLM756P module can charge the over-discharged battery. The charging process includes trickle
charge, constant current, and constant voltage charging.
 Trickle charge: it is divided into 2 parts, trickle charge-A: charge current 90mA when the battery
voltage is lower than 2.8V; trickle charge-B: charge current 450mA when the battery voltage is
between 2.8V~3.2V;
 Constant current charging: When the battery voltage is between 3.2V and 4.2V, the constant current
is charged, the charging current is 1.44A when the adapter is charging, and the charging current is
450mA when charging the USB;
 Constant voltage charging: When the battery voltage reaches 4.2V, the constant voltage is charged,
the charging current is gradually decreased, the charging current is reduced to about 100mA, and the
charging is cut off.
4.11.3 BAT _THERM
The SLM756P module has battery temperature detection and can be implemented by BAT_THERM
(46PIN). This requires the internal integration of a 10KΩ 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.
Adapter or USB