A5191HRTNGEVB
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5
Power Supply and References
Power Supply
Figure 4. Supply Voltage and Power on Reset
The A5191HRTNGEVB is designed for a nominal
voltage of 3 V. However, A5191HRT 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 on this.
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 3.
Table 3. MODULE CURRENT CONSUMPTION
Symbol
Condition
Current Consumption
I
DD
V
DD
= 2.78 V, Transmit
428
m
A
I
DD
V
DD
= 2.78 V, Receive
417
m
A
I
DD
V
DD
= 3 V, Transmit
443
m
A
I
DD
V
DD
= 3 V, Receive
419
m
A
I
DD
V
DD
= 6 V, Transmit
837
m
A
I
DD
V
DD
= 6 V, Receive
781
m
A
I
DD
V
DD
= 3 V, Transmit, Ext. Osc.
362
m
A
I
DD
V
DD
= 3 V, Receive, Ext. Osc.
350
m
A
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.
It is advised to use a voltage supervisor such as CAT808
to prevent the modem to begin operation when the supply
voltage is not yet reliable. This will guarantee correct
operation of the digital circuitry.
The voltage supervisor will keep the RESETB pin low
until its threshold value is reached (2.7 V on the
A5191HRTNGEVB). This ensures that some time has
passed after the supply voltage reaches the turn−on voltage
level of 2.5 V.
The RESETB and VDD pin signals during startup are
shown in Figure 5. The measured start−up delay is 2.6 ms.