Pcm And I2C Interface - Quectel UC20 Hardware Design


It is important to route the USB signal traces as differential pairs with total grounding. The impedance
of USB differential trace is 90ohm.

Do not route signal traces under crystals, oscillators, magnetic devices and RF signal traces. It is
important to route the USB differential traces in inner-layer with ground shielding not only upper and
lower layer but also right and left side.

Pay attention to the influence of junction capacitance of ESD component on USB data lines. Typically,
the capacitance value should be less than 2pF.

Keep the ESD components as closer to the USB connector as possible.
NOTE
UC20 module can only be used as a slave device.
The USB interface is recommended to be reserved for firmware upgrade in your design. The following
figure shows the recommended test points.

3.13. PCM and I2C Interface

UC20 provides one Pulse Code Modulation (PCM) digital interface for audio design, which supports the
following modes:

Primary mode (short sync, works as both master and slave)

Auxiliary mode (long sync, works as master only)
UC20_Hardware_Design
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Module
USB_VBUS
USB_DM
USB_DP
VBAT_BB
VBAT_RF
PWRKEY
GND
Figure 25: Test Points of Firmware Upgrade
Confidential / Released
UMTS/HSPA Module Series
UC20 Hardware Design
Connector
USB_VBUS
USB_DM
USB_DP
VBAT
PWRKEY
GND
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