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UMTS/HSPA Module Series

UC20 Hardware Design

UC20_Hardware_Design Confidential / Released 30 / 82

2A at least. If the voltage drop between the input and output is not too high, it is suggested to use a LDO

to supply power for 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 a power supply.

The following figure shows a reference design for +5V input power source. The designed output for the

power supply is about 3.8V and the maximum load current is 3A.

DC_IN

MIC29302WU U1

OUT

GND

ADJ

2 4

VBAT

100nF

470uF

100nF

100K

47K

470uF

470R

51K

Figure 8: Reference Circuit of Power Supply

3.6.4. Monitor the Power Supply

You can use the AT+CBC command to monitor the VBAT_BB voltage value. For more details, please

refer to document [1].

3.7. Turn on and off Scenarios

3.7.1. Turn on Module Using the PWRKEY

The following table shows the pin definition of PWRKEY.

Table 7: PWRKEY Pin Description

Pin Name

Pin No.

Description

DC Characteristics

Comment

PWRKEY

Turn on/off the module.

max = 2.1V

min = 1.3V

max = 500mV

Pull-up to 1.8V internally

with 200kΩ resistor.

When UC20 is in power down mode, it can be turned on to normal mode by driving the PWRKEY pin to a

low level at least 100ms. It is recommended to use an open drain/collector driver to control the PWRKEY.

After STATUS pin (require external pull-up) outputting a low level, PWRKEY pin can be released. A simple

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