Power Supply; Decrease Voltage Drop - Quectel EM05 Hardware Design

3.5. Power Supply

The following table shows pin definition of VCC pins and ground pins.
Table 6: Definition of VCC and GND Pins
Pin No.
2, 4, 70, 72, 74
3, 5, 11, 27, 33,
39, 45, 51, 57, 71,
73

3.5.1. Decrease Voltage Drop

The power supply range of the module is from 3.135V to 4.4V. Please make sure that the input voltage will
never drop below 3.135V. The following figure shows the voltage drop during Tx power in 3G and 4G
networks.
VCC
Min.3.135V
To decrease voltage drop, a bypass capacitor of about 220µF with low ESR (ESR=0.7Ω) should be used,
and a multi-layer ceramic chip capacitor (MLCC) array should also be reserved due to its ultra-low ESR.
It is recommended to use three ceramic capacitors (100nF, 33pF, 10pF) for composing the MLCC array,
and place these capacitors close to VCC pins. The main power supply from an external application has to
be a single voltage source. The width of VCC trace should be no less than 2mm. In principle, the longer
the VCC trace is, the wider it will be.
In addition, in order to get a stable power source, it is suggested that you should use a zener diode which
dissipation power is more than 0.5W. The following figure shows reference circuit of VCC.
EM05_Hardware_Design
Pin Name I/O
VCC PI
GND
Tx power
Figure 5: Power Supply Limits during Tx power
Power Domain
3.135V~4.4V
Tx power
Drop
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LTE Module Series
EM05 Hardware Design
Description
3.3V DC supply
Ground
Ripple
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