M20 Hardware Design
3.5 Charging interface
The module has OPTIONALLY integrated a charging circuit for rechargeable Li-Ion or Lithium
Polymer battery, which makes it very convenient for application to manage its battery charging.
A common connection is shown in Figure 13.
Module
VCHG
VBAT
DC5V
Battery pack
4.7uF
Figure 13: Charging circuit connection
The charging function is not supported in standard M20 module. If customer needs this function, it
would be necessary to contact Quectel. Furthermore, when battery charging is done by the
charging function supported by the module, the VBAT would be mainly supplied by the battery
and the external power source is used to charging the battery. In this case, when the battery is
charged full, the charging circuit will stop working, but the charging function would be
re-activated when the battery voltage drops to certain level. The battery is either in discharging
mode or in charging mode, which could significantly shorten its life cycle. Therefore, it should
always be cautious to use the internal charging function in M2M application.
A more suitable way to charging battery in M2M application is to use an external charging circuit
which can charge the battery and put it into idle mode when battery is full. The VBAT is supplied
by external power source instead of the battery, but when the external power source is cut off the
battery will supply to the VBAT immediately. A reference block diagram for this design is shown
in Figure 14.
M20_HD_V1.01
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Quectel