Product Info

LTE Standard Module Series
EG91 Series Hardware Design
EG91_Series_Hardware_Design
56 / 102
Pin Name
Pin No.
I/O
Description
USB_BOOT
75
DI
Force the module to enter
emergency download mode
Table 21: Default Behaviors of RI
State Response
Idle RI keeps at high level
URC RI outputs 120ms low pulse when a new URC returns
3.18. USB_BOOT Interface
EG91 series module provides a USB_BOOT pin. Customers can pull up USB_BOOT to 1.8V before
VDD_EXT is powered up, and the module will enter emergency download mode when it is powered on. In
this mode, the module supports firmware upgrade over USB interface.
Table 22: Pin Definition of USB_BOOT Interface
Comment
1.8V power domain.
Active high.
It is recommended to
reserve test point.
The following figures show the reference circuit of USB_BOOT interface and timing sequence of entering
emergency download mode.
Module
VDD_EXT
USB_BOOT
Test point
4.7K
Close to test point
TVS
Figure 28: Reference Circuit of USB_BOOT Interface