Decrease Voltage Drop - Quectel EG91 Series Hardware Design

Table 6: Pin Definition of VBAT and GND
Pin Name Pin No.
VBAT_RF 52, 53
VBAT_BB 32, 33
3, 31, 48, 50,
54, 55, 58, 59,
GND 61, 62, 67~74,
79~82, 89~91,
100~106

3.6.2. Decrease Voltage Drop

The power supply range of the module is from 3.3V to 4.3V. Please make sure that the input voltage will
never drop below 3.3V. 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 100µF with low ESR (ESR=0.7Ω) should be used,
and a multi-layer ceramic chip (MLCC) capacitor 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 VBAT_BB/VBAT_RF pins. The main power supply 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 1mm, and the width of VBAT_RF trace should be no
less than 2mm. In principle, the longer the VBAT trace is, the wider it will be.
In addition, in order to avoid the damage caused by electric surge and ESD, it is suggested that a TVS
diode with low reverse stand-off voltage V
current I should be used. The following figure shows the star structure of the power supply.
PP
EG91_Hardware_Design
Description
Power supply for module's
RF part.
Power supply for module's
baseband part.
Ground
Burst
Transmission
Drop
, low clamping voltage V
RWM
LTE Standard Module Series
EG91 Hardware Design
Min. Typ.
3.3 3.8
3.3 3.8
- 0
Burst
Transmission
and high reverse peak pulse
C
Max. Unit
4.3 V
4.3 V
- V
Ripple
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