NCN5192NGEVB
http://onsemi.com
5
Power Supply and References
Power Supply
The NCN5192NGEVB is designed for a nominal voltage
of 3 V. However, NCN5192 can be operated up to 6 V. For
optimal functioning of the board, the values of several
resistors should be changed for operation at voltages higher
than 3 V (see the sections on reference voltages and bias for
more information).
Figure 4. Supply Voltage and Power on Reset
Current consumption of the module is very limited,
making it ideal to be battery or loop-powered.
Measurements of the power consumption of the module are
listed in Table 1.
The module will use less power when clock signal is
applied externally, as this allows the modem to shut down
the oscillator circuit. As is to be expected, a higher supply
voltage increases current consumption.
The NCN5192 includes an internal voltage supervisor.
This will guarantee correct operation of the digital circuitry
during start-up. All that is required for using this supervisor
is an external resistor divider (R
25
, R
26
). The voltage
supervisor compares the voltage offered by the resistor
divider on the VPOR pin to AREF. The resistor divider
should be dimensioned such that at the desired turn-on point
of the voltage supervisor, the VPOR pin is equal to AREF.
On the evaluation board the resistor divider is dimensioned
to make the POR trip at 2.8 V.
The voltage supervisor will keep the RESETB pin low
until its threshold value is reached, and will then wait an
additional minimum of 35 ms until it releases the RESETB.
This ensures that some time has passed after the supply
voltage reaches the turn-on voltage.
The RESETB en V
DD
pin signals during startup are
shown in Figure 5. The measured start-up delay is 48 ms.
Figure 5. Power (Light Blue) and RESETB (Dark Blue) Waveform during Startup, Showing 48 ms Startup Delay
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