Sunsea AIoT SIMCom SIM7075G User Manual page 67

B. Design check list
Table 44: Schematic Check List
NO. Items
1 Insure the supply voltage for VBAT is withintherange
Insure the maximum supply current for VBAT is above its consumption when it is maximum
2
power emission.
Insure the capacitor for VBAT is meet its request, in order to avoid the voltage drop exceed
3
300mV.
Insure the input signal for PWRKEY pin meet its electrical level match. It recommended use
4
BJT to shift its level.
Insure the netconnections of UART be correctness according to signal direction. Insure the
5 signal for UART pins meet its electrical level match. It recommended use BJT or level shift IC
to shift its level.
Insure USB port had used TVS to protect signal. And the junction capacity of TVS for DP/DM
6
must be less than 3pf.
Insure SIM card signal had used TVS to protect. And the junction capacity of TVS must be
7
less than 50pf.
8 The power supply of the active antenna should be controlled and closed.
9 Insure I2C signal had used resistors 1Kohm pull up to VDD_EXT if used.
The electrical level of all GPIOs is 1.8V. Insure the signal for GPIO pins meet its electrical level
10
match.
11 The input range of ADC is 0V~1.875V. Insure the input signal never exceed its range.
User must pull up DTR when module enters into sleep mode. Insure DTR can be controlled by
12
host.
Suggesting to reserve test ports for VDD_EXT and BOOT_CFG. BOOT_CFG should keep
13
open before boot up.
LTE main ANT should Keep TVS to prevent ESD destroyed. And the TVS should be Low
14
junction capacitance.
15 LTE main ANT should have a PI type matching to debug antenna
Table 45: PCB Layout Check List
NO. Items
1 Insure the capacitor placement for VBAT be near module pin.
Insure VBAT trace width be greater than 2mm. If NB only, insure VBAT trace width be greater
2
than 1mm. And the VIA number must be enough for getting through the current.
Insure the return path GND of the power supply is good. Insure the connectivity between
3
module GND and mother board GND is good.
Insure PCM trance is protected by GND, and keep it far from interference source, such as
4
power supply trace, USB trace, RF trace and so on.
Insure USB trance is protected by GND, and keep it far from interference source, such as
5 power supply trace, RF trace and so on. Insure DM/DP trace is differential routing, and
differential impedance is 90 ohm.
6 Insure ADC trance is protected by GND.
Insure SIM card signal trance is protected by GND. Especially SIM_CLK must be protected
7
alone. And avoid signal trace branched Routing.
Insure TVS avoid bypass. The trace must go through TVS pad first, and then arrived module
8
pad.
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