Users Manual

LTE Standard Module Series
EC25 Hardware Design
EC25_Hardware_Design
68
/ 130
Module
USB_BOOT
VDD_EXT
4.7K
Test points
TVS
Close to test points
Figure 31: Reference Circuit of USB_BOOT Interface
V
IL
≤
0.5V
V
H
=0.8V
VBAT
PWRKEY
≥
500ms
RESET_N
VDD_EXT
About 100ms
USB_BOOT
USB_BOOT can be pulled up to 1.8V before
VDD_EXT Is powered up, and the module will
enter emerge ncy download mode when i t is
powered on.
NOTE 1
Figure 32: Timing Sequence for Entering Emergency Download Mode
1. Please make sure that VBAT is stable before pulling down PWRKEY pin. It is recommended that the
time between powering up VBAT and pulling down PWRKEY pin is no less than 30ms.
2. When using MCU to control module to enter the emergency download mode, please follow the above
timing sequence. It is not recommended to pull up USB_BOOT to 1.8V before powering up VBAT.
Connect the test points as shown in Figure 31 can manually force the module to enter download
mode.
NOTES