Vrtc - Sunsea AIoT SIMCom SIM5800 Hardware Design

SIM5800 also have a RESET pin used to reset the module. This function is used as an emergency reset. Users can
pull the RESET pin to the ground, and then the module will restart.
Note: This function requires software modification. Please contact SIMCom.
The typical value of RESET pin high level is 1.8V, so for the 3V or 3.3V condition, customer could not directly
use MCU's GPIO to driver this pin directly, refer to the following table for RESET hardware parameters.
Table 4: Electronic characteristic of the RESET Pin
Pin Name
RESET
4.3

VRTC

VRTC is the power supply for RTC circuit and charger output for coin cell or backup battery. If RTC support is
needed when the battery is removed, a qualified coin cell or keep-alive capacitor is required on the VRTC pin.
When VBAT is present and valid, coin cell charging is enabled through software control and powered from VBAT.
Reference circuits are shown in the following figures:

External capacitor backup
Large-capacitance

Non-chargeable battery backup
SIM5800_Hardware Design_V1.01
Smart Machine Smart Decision
Reset
Figure 12: Reset circuit
Symbol
V
IH
V
IL
T
pull-down
Capacitor
Figure 13: RTC supply from capacitor
MT6350
100R
Module
Min Typ
1.4 -
- -
TBD TBD
Module
VRTC
1K
24
Max unit
- V
0.2 V
- s
RTC
Core
2018-10-08