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3.9. USB Interface
SC20-WL contains one integrated Universal Serial Bus (USB) interface which complies with the USB 2.0
specification and supports high speed (480 Mbps) and full speed (12 Mbps) 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 6: Pin Definition of USB Interface
Pin Name
Pin No.
USB_VBUS
141, 142
USB_DM
13
USB_DP
14
USB_ID
16
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 5.0V. SC20-WL 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.
USB_VUSB
USB_DM
USB_DP
Module
Figure 13: USB Interface Reference Design (OTG is not Supported)
SC20-WL_Hardware_Design
I/O
Description
PI
USB power supply
IO
USB differential data bus (minus)
IO
USB differential data bus (plus)
AI
USB ID detection
C1
D1
D2
100nF
ESD ESD ESD
Smart Wi-Fi Module Series
SC20-WL Hardware Design
1
VUSB
2
USB_DM
3
USB_DP
4
USB_ID
5
D3
GND
Comment
4.35V~6.3V
Typical 5.0V
Require differential
impedance of 90Ω
High level by default
37 / 81
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