Neoway WM620 - Reset; Figure 3-8 Reset Circuit

WM620 Hardware User Guide
Copyright © Neoway Technology Co., Ltd
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3.1.5 RESET
RESET is a hard reset input pin that is pulled up internally by a resistance and activated by low level
signal.
Low level pulse longer than 20 ms can reset the WM620 module. After resetting the module, power on
the module again. The recommended reset pulse is 50 ms, and it cannot exceed 2 seconds. Otherwise, the
WM620 module will be powered off.
If the ON_OFF pin is at low level or connected to GND, the WM620 can restart automatically once
resetting the module. Figure 3-8 shows the reference design of reset circuit.
Figure 3-8 Reset circuit
The RESET pin is sensitive to pulse. Place a 10 nF filter capacitor close to the pin to filter natural
interference. Ensure complete ground around the trace of this pin and dig holes on both side of the trace.
If the level from the external MCU exceeds 1.8 V, OC control is recommended. Leave the pin not
connected if not use it.
The module works in complicated environment. It might encounter halt or other abnormities. Therefore,
take automatic restore into consideration when designing products. The following two methods are
recommended:
 Control the RESET pin (emergency shutdown) to set low level for hard shutdown.
 Perform the soft shutdown process by referring to Neo_WM620 WCDMA Module AT Command Set.
Five seconds later, power off or reset the module. Otherwise, the program might be damaged during
the hard shutdown if the module is reading or writing information in the memory.
VT2
MCU RESET
10nF
C3
R6 and C3 are close to the pin.
R5
R6
R6
100
WM620
RESET
10K
2K