N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
10
⚫
Select an enhanced p-MOSFET at Q1, of which the maximum safe operating voltage and drain
current is high and Rds is low.
⚫
Select a common NPN bipolar transistor or a digital NPN bipolar transistor at Q2. If selecting
common NPN bipolar transistor, reserve enough tolerances of resistors at R1 and R2 in design,
especially for the situation in which operating voltage of the bipolar transistor might increase in
low temperature.
⚫
Place TVS2 close to the input interface of the power supply to clamp the surge voltage before it
enters back-end circuits. Therefore, the back-end components and the module are protected.
⚫
Place C3 close to the module. A large bypass tantalum capacitor (220 μF or 100 μF) or
aluminum capacitor (470 μF or 1000 μF) is expected at C1 to reduce voltage drops during
bursts. Its maximum safe operating voltage should be larger than 1.5 times the voltage across
the power supply.
⚫
Place low-ESR bypass capacitors close to the module to filter out high-frequency noise from the
power supply.
The following design is recommended for 4.3 V to 5.5 V input.
Figure 3-3
Recommended design 3
U1
C1
100
μF
TAN
R1
100 k
Ω
C2
0.1
μF
R2
47.5 k
Ω
C3
470
μF
TAN
C5
0.1
μF
TVS2
5V
EN
VIN
VOUT
ADJ
C4
10
μF
C6
100 pF
C6
33 pF
GND
GND
PWR_EN
VIN (5V)
VBAT
⚫
Design with LDO is more simple and efficient when the output of power supply is close to the
permissible voltage across VBAT.
⚫
Select an LDO that can output a current larger than 2 A at U1 to ensure the performance of the
module. MIC29302WU is recommended.
⚫
Place TVS2 close to the input interface of the power supply to clamp the surge voltage before it
enters back-end circuits. Therefore, the back-end components and the module are protected.
⚫
Place C3 close to the module. A large bypass tantalum capacitor (220 μF or 100 μF) or
aluminum capacitor (470 μF or 1000 μF) is expected to reduce voltage drops during bursts. Its
maximum safe operating voltage should be larger than 1.5 times the voltage across the power
supply.