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In order to offer good ESD protection, it is recommended to add a TVS diode array. For more
information of TVS diode, please visit http://www.onsemi.com. The ESD protection device should be
placed as close to USIM card connector as possible, and make sure the USIM card signal lines go
through the ESD protection device first and then to the module. The 22Ω resistors should be
connected in series between the module and the USIM card connector so as to suppress EMI
spurious transmission and enhance ESD protection. Please note that the USIM peripheral circuit
should be close to the USIM card connector.
Place the RF bypass capacitors (33pF) close to the USIM card connector on all signal traces to
improve EMI suppression.
3.10. ADC Interface
The module provides a 10-bit ADC input channel to read the voltage value. The interface is available in
active mode, and has to be woken up first to ensure availability in sleep modes.
Table 14: Pin Definition of ADC Interface
Pin Name
Pin No.
ADC0
9
3.11. RI Behaviors
When there is a message received or URC output, the module will notify DTE through RI pin.
Table 15: RI Signal Status
Module Status
Idle
SMS
URC
BC66-NA_Hardware_Design
Description
Analog to digital converter interface
RI Signal Level
RI keeps in high level
When an SMS is received, RI outputs 120ms low pulse first and then changes to
high level and starts data output.
When URC is incoming, RI outputs 120ms low pulse first and then changes to
high level and starts data output.
NB-IoT Module Series
BC66-NA Hardware Design
Sample Range
0V ~ 1.4V
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