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Product Technical Specification & Customer Design Guidelines
54
Proprietary and Confidential - Contents subject to change
Note: Startup time is the time after power-up when the modem is ready to begin the
enumeration sequence.
Transmit power waveform (GSM)
As shown in
Figure
6-3, at maximum GSM transmit power, the input current can
remain at 2.4 A for up to 25% of each 4.6 ms GSM cycle (1.15 ms) after reaching
an initial peak of 2.75 A (average over 100 µs, with an instantaneous peak current
of 3.5 A). For class 12 operation, the peak could remain for 2.3 ms (four
timeslots).
The 2.4 A current draw is for 50 ohm systems (1:1 VSWR). For worst-case
antenna designs (3.5:1 VSWR), the current draw could increase to 2.75 A, as
shown in the diagram. Beyond 3.5:1 VSWR, the current draw could increase to
3.5 A.
2.75A peak
2.75
2.4
Current
(A)
0.15
25 µs
1.15 ms
Figure 6-3: GSM transmit power waveform (class 10 operation)
Power supply noise
Noise in the power supply can lead to noise in the RF signal.
The power supply ripple limit for the module is no more than 200 mVp-p 1 Hz to
100 kHz. This limit includes voltage ripple due to transmitter burst activity.
Additional decoupling capacitors can be added to the main VCC line to filter noise
into the device.
SED (Smart Error Detection)
The module uses a form of SED to track premature modem resets.
•
Module tracks consecutive resets occuring soon after power-on.
•
After a sixth consecutive reset, the module waits in boot-and-hold mode for a
firmware download to resolve the power-cycle problem.
3.5:1 VSWR = 2.75A
1:1 VSWR = 2.40A
4.6 ms
2400089
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