M50 Hardware Design
M50_HD_V2.0
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The other way to control the PWRKEY is using a button directly. A TVS component is
indispensable to be placed nearby the button for ESD protection. When pressing the key,
electrostatic strike may generate from finger. A reference circuit is shown in the following figure.
S1
PWRKEY
TVS1
Close to S1
Figure 7
: Turn on the module using keystroke
The power-on scenarios is illustrated as the following figure.
EMERG_OFF
(INPUT)
VDD_EXT
(OUTPUT)
V
IL
<0.1*VBAT
V
IH
> 0.6*VBAT
VBAT
PWRKEY
(INPUT)
54ms
STATUS
(OUTPUT)
800ms
>1s
OFF
BOOTING
MODULE
STATUS
RUNNING
2
1
Figure 8:
Timing of turning on system
①
Make sure that VBAT is stable before pulling down PWRKEY pin. The time between them
is recommended 30ms.
②
EMERG_OFF should be floated when it is unused
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