Product Info

LTE Standard Module Series
EG91 Hardware Design
EG91_Hardware_Design 53 / 96
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 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
Pin Name
Pin No.
I/O
Description
Comment
USB_BOOT
75
DI
Force the module to enter
emergency download mode
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
USB_BOOT
VDD_EXT
4.7K
Test point
TVS
Close to test point
Figure 28: Reference Circuit of USB_BOOT Interface