Neo_M680 GPRS Module Hardware User Guide
Copyright © Neoway Technology Co., Ltd
10
Figure 3-2 shows a recommended power supply design for the module.
Figure 3-2
Capacitors used for the power supply
Power Supply
GPRS Module
Close to the pin of the module
D1 C1
C2 C3
C4
VBAT
Current testing point
I_max
C5
In the circuit, you can use TVS at D1 to enhance the performance of the module during a burst. SMF5.0AG
(Vrwm=5V&Pppm=200W) is recommended. 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 together
with C2 (10 μF capacitor). In addition, you need to add 0.1 μF, 100 pF, and 33 pF filter capacitors to enhance
the stability of the power supply.
A controllable power supply is preferable if used in harsh conditions. The module might fail to reset in
remote or unattended applications, or in an environment with great electromagnetic interference (EMI). You
can use the EN pin on the LDO or DC/DC chipset to control the switch of the power supply as shown in
Figure 3-3.
MIC29302WU in the following figure is an LDO and outputs 3 A current to ensure the performance of the
module.
Figure 3-3
Reference design of power supply control
The alternative way is to use a p-MOSFET to control the module's power, as shown in Figure 3-4
When
the external MCU detects the exceptions such as no response from the module or the disconnection of
GPRS, power off/on can rectify the module exceptions. In Figure 3-4, the module is powered on when
GPRS_EN is set to high level.
VCC_IN_5V
GPRS_EN
VBAT
100 uF
TAN
0.1 uF
TVS
5V
10 uF
470uF
TAN
10K
4.75K
VOUT
MIC29302WU
EN
VIN
ADJ
0.1 uF 100pF 33pF
