Telit Wireless Solutions LE915A P Series, Руководство по конструкции аппаратуры

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LE915Ax-P
Hardware Design Guide
1VV0301680 Rev. 2
Page 21 of 51 2021-10-04
Not Subject to NDA
5. INTERFACE DETAILS
Power On.Off and Reset Control
The Telit module can be turned on/off by means of the MODULE_PWR_EN port.
The module enters Power on Reset mode when the RESET_N is set logical LOW.
While the device power-on sequence is still in progress, the two conditions below must
be avoided:
•
The main power supply voltage shall not be drop below minimum operating
voltage.
•
None of the two pins (MODULE_PWR_EN, RESET_N) can transition to LOW.
Table 12 : 1.8V power output
5.1.1. Power On Sequence
The power supply should be stable enough before releasing the MODULE_PWR_EN to
HIGH to turn the module.
Step 1: Supply VBAT1 and VBAT2.
Step 2: Wait until the VBAT1 and VBAT2 power supply are stable enough as over than 3.3V
minimum operating voltage.
Step 3: Set RESET_N port to HIGH
Step 4: Wait until the URC +SYSSTART is received. Which is typically in the range of 20 ~
60 seconds in normal operating mode. In case of boot following a SW upgrade, it
takes up to 90 seconds. If there is no response beyond 60/90 Sec, turn off the
VBAT1 and VBAT2 to make it zero voltage, then retry from the step 1.
5.1.2. Power Off Sequence
To safely power off the module, it is recommended to wait at least 10 seconds after
sending the AT+SQNSSHDN shutdown command before turning off VBAT1/2.
Pin
Signal I/O
Function description
64 MODULE_PWR_EN I Active HIGH to power on.
63 RESET_N I
Active LOW for reset while MODULE_PWR_EN is high in normal operating
mode. This signal should be pulled by 100kohms to 1.8V.
The minimum hold time for reset is 1uS.