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layer and ground planes above and below.
⚫
Pay attention to the selection of the ESD component on the USB data line. Its stray capacitance
should not exceed 2 pF and should be placed as close as possible to the USB connector.
4.3. USB_BOOT Interface
The module provides a USB_BOOT pin. You can pull up USB_BOOT to VDD_EXT before power-up and
the module will enter download mode when it is turned on. In this mode, the module supports firmware
upgrade over USB interface.
Table 12: Pin Definition of USB_BOOT Interface
Pin Name
Pin No.
USB_BOOT
75
The following figure shows a reference circuit of USB_BOOT interface.
EG915U_Series_Hardware_Design
I/O
Description
Control pin for module to enter
DI
download mode
Module
USB_BOOT
TVS
Figure 19: Reference Circuit of USB_BOOT Interface
Comment
1.8 V power domain.
Active high.
A circuit that enables the module to
enter the download mode must be
reserved.
Test point
2
1
4.7K
3
GND
Close to test point
LTE Standard Module Series
VDD_EXT
42 / 81
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