User Manual

MeiG_SLM550_Hardware Design Manual

MeiG Smart Technology Co., Ltd 39/89

Note：

If the user does not use battery power, please note that a 47K resistor is connected to the 134 pin

(BAT_THERM) of the module and pulled down to GND to prevent the software from judging the

abnormal battery temperature after the module is turned on, resulting in shutdown. The connection

diagram is as follows:

Figure 10 Connection diagram when not powered by battery

The user can directly use a 3.7V lithium ion battery to power the module, or use a nickel-cadmium or

nickel-manganese battery to power the module, but please note that the maximum voltage of the nickel-

cadmium or nickel-manganese battery cannot exceed the maximum allowable voltage of the module,

otherwise the module will be damaged. When using a battery, the impedance between the VBAT pin

and the battery should be less than 150mΩ.

4.1.1 Power Pin

The VBAT pin (1, 2, 145, 146) is used for power input. In the user's design, pay special attention to the

design of the power supply section to ensure that the VBAT does not fall below 3.4V even when the

module consumes 2A. If the voltage drops below 3.4V, the module may shut down. The PCB layout

from the VBAT pin to the power supply should be wide enough to reduce the voltage drop in the

transmit burst mode.

Figure 11 VBAT lowest voltage drop

4.2 Power on and off

Do not turn on the module when the module's temperature and voltage limits are exceeded. In extreme

cases, such operations can cause permanent damage to the module.

4.2.1 Module Boot

The user can power on the module by pulling the KYPD_PWR_N pin (114) low. The pull-down time is at

least 5 seconds. This pin has been pulled up to 1.8V in the module. The recommended circuit is as

47K