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3.4.3. Reference Design for Power Supply
The power design for the module is very important, as the performance of module largely depends on the
power source. The power supply of SC20 series should be able to provide enough current of at least 3 A.
If the voltage drop between the input and output is not too high, it is suggested to use an LDO to supply
power for the module. If there is a big voltage difference between the input source and the desired output
(VBAT), a buck converter is preferred to be used as the power supply.
The following figure shows a reference design for +5 V input power source which adopts an LDO
(MIC29302WU) from MICREL. The typical output voltage is 3.8 V and the maximum load current is 3.0 A.
Figure 5: Reference Circuit of Power Supply
1. It is recommended to switch off the power supply when the module is in abnormal state, and then
switch on the power to restart the module.
2. The module supports battery charging by default. If the above power supply design is adopted, make
sure the charging function is disabled by software, or connect VBAT to a Schottky diode in series to
avoid the reverse current to the power supply chip.
3.5. Turn on and off Scenarios
3.5.1. Turn on with PWRKEY
The module can be turned on by driving PWRKEY pin low for at least 1.6 s. PWRKEY pin is pulled to
1.8 V internally. It is recommended to use an open drain/collector driver to control the PWRKEY. A simple
reference circuit is illustrated in the following figure.
NOTE
