Quectel EG91 Series Hardware Design page 57

VBAT
PWRKEY
VDD_EXT
USB_BOOT
RESET_N
Figure 29: Timing Sequence for Entering into Emergency Download Mode
NOTES
1. Please make sure that VBAT is stable before pulling down PWRKEY pin. The time between them is
no less than 30ms.
2. When using MCU to control module to enter into the emergency download mode, follow the above
timing sequence. It is not recommended to pull up USB_BOOT to 1.8V before powering up the VBAT.
Short the test points as shown in Figure 28 can manually force the module to enter into download
mode.
EG91_Hardware_Design
NOTE
≥500ms
V IL ≤0.5V
About 100ms
Setting USB_BOOT to high level between VBAT rising
on and VDD_EXT rising on can let the module enter
into emergency download mode.
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V H =0.8V
LTE Module Series
EG91 Hardware Design