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Automotive Module Series
AG521R-NA QuecOpen Hardware Design
AG521R-NA_QuecOpen_Hardware_Design 41 / 92
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
Burst
Transmission
Min.3.3V
Ripple
Drop
Burst
Transmission
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
C1
100 µF
+
3
D1
C
33 pF
C
100 nF
2
C
10 pF
4
VBAT_BB
Module
VBAT_RF
C6
100 nF
C7
33 pF
C8
10 pF
+
C
5
100 µF
Figure 8: VBAT Reference Design