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3.5.3. Reference Design for Power Supply
Power design for the module is very important, as the performance of the module largely depends on the
power source. The power supply should be able to provide sufficient current up to 2A at least. If the
voltage drop between the input and output is not too high, it is suggested that an LDO should be used 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 +5V input power source. The typical output of the power
supply is about 3.8V and the maximum load current is 3A.
DC_IN
470uF
100nF
3.6. Turn on and off Scenarios
3.6.1. Turn on Module Using the PWRKEY
The following table shows the pin definition of PWRKEY.
Table 7: PWRKEY Pin Description
Pin Name
Pin No.
PWRKEY
21
When UC200T-EM is in power down mode, it can be turned on to normal mode by driving the PWRKEY
pin to a low level for at least 500ms. It is recommended to use an open drain/collector driver to control the
PWRKEY. After STATUS pin (require external pull-up) outputs a low level, PWRKEY pin can be released.
A simple reference circuit is illustrated in the following figure.
UC200T-EM_Hardware_Design
MIC29302WU
2
IN
51K
4.7K
VBAT_EN
47K
Figure 5: Reference Circuit of Power Supply
I/O
DI
UMTS/HSPA(+) Module Series
UC200T-EM Hardware Design
4
OUT
100K
1%
47K
1%
Description
Turn on/off the module
470R
470uF
100nF
Comment
VBAT power domain
VBAT
25 / 68
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