Product Info

Smart LTE Module Series
SC20 Hardware Design
SC20_Hardware_Design 43 / 130
If thermistor is not available in the battery, or adapter is utilized for powering module, then there is only
need for VBAT and GND connection. In this case, the system may mistakenly judge that the battery
temperature is abnormal, which will cause battery charging failure. In order to avoid this, VBAT_THERM
should be connected to GND via a 47KΩ resistor. If VBAT_THERM is unconnected, the system will be
unable to detect the battery, making battery cannot be charged.
VBAT_SNS pin must be connected. Otherwise, the module will have abnormalities in voltage detection,
as well as associated power on/off and battery charging and discharging issues.
3.9. USB Interface
SC20 contains one integrated Universal Serial Bus (USB) interface which complies with the USB 2.0
specification and supports high speed (480Mbps) and full speed (12Mbps) modes. The USB interface is
used for AT command communication, data transmission, software debugging and firmware upgrade.
The following table shows the pin definition of USB interface.
Table 10: Pin Definition of USB Interface
USB_VBUS can be powered by USB power or adapter. It can also be used for detecting USB connection,
as well as for battery charging via the internal PMU. The input voltage of power supply ranges from 4.35
to 6.3V, and the typical value is 5V. SC20 module supports charging management for a single Li-ion
battery, but varied charging parameters should be set for batteries with varied models or capacities. The
module is available a built-in linear-charging circuit which supports maximally 1.44A charging current.
The following are two USB interface reference designs for customers to choose from.
Pin Name
Pin No.
I/O
Description
Comment
USB_VBUS
141, 142
PI
USB power supply
4.35V~6.3V.
Typical 5.0V.
USB_DM
13
IO
USB differential data bus (minus)
Require differential
impedance of 90Ω
USB_DP
14
IO
USB differential data bus (plus)
USB_ID
16
AI
USB ID detection
High level by default