Decrease Voltage Drop - Quectel QuecOpen AG521R-NA Hardware Design

3.6.2. Decrease Voltage Drop

The power supply range of the module is from 3.3 to 4.3 V. Please make sure that the input voltage will never drop
below 3.3 V. The following figure shows the voltage drop during burst transmission in 2G network. The voltage
drop will be less in 3G and 4G networks.
VBAT
Min.3.3V
Figure 7: Power Supply Limits during Burst Transmission
To decrease voltage drop, a bypass capacitor of about 100 µF with low ESR should be used, and a multi-layer
ceramic chip capacitor (MLCC) array should also be reserved due to its low ESR. It is recommended to use three
ceramic capacitors (100 nF, 33 pF, 10 pF) for composing the MLCC array, and place these capacitors close to
VBAT pins. DC_3V8 from an external application has to be a single voltage source and can be expanded to two sub
paths with star structure. The width of VBAT_BB trace should be no less than 1 mm. The width of VBAT_RF trace
should be no less than 2 mm. In principle, the longer the VBAT trace is, the wider it will be.
In addition, in order to get a stable power source, it is suggested to use high power TVS diode to prevent static
electricity, and place them as close to the VBAT pins as possible. The following figure shows a reference design of
VBAT power supply pins.
DC_3V8
D1
100 µ F
AG521R-NA_QuecOpen_Hardware_Design
Burst
Transmission
C1
+
C 4
C 2 C 3
10 pF
100 nF 33 pF 100 µ F
Figure 8: VBAT Reference Design
AG521R-NA QuecOpen Hardware Design
Burst
Transmission
Drop
C 5
+
C6 C7 C8
100 nF 33 pF 10 pF
Automotive Module Series
Ripple
VBAT_BB
VBAT_RF
Module
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