CalAmp SMC-GPRS Series, Руководство пользователя

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001-0004-829 Rev00
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Power Supply Issues
Because of its high current consumption during transmission, power supply design for the SMC-GPRS
modem should be focused on the transmitting mode (dedicated mode). More information can be
found in related document
[3] .
Power Consumption for GSM/GPRS Cell Module
Due to the maximum RF power levels of approx. 2W the power supply current is modulated with 2A
(approx.) pulses of 0.577ms every 4.6ms. During the receive only time period, current GSM call
consumption is lower than 100mA. An example current profile is illustrated in Figure 1. The
measured values refer to the GSM 900MHz band at maximum power level with a real 50Ohm load.
Figure 1: Current Peak Example
During a GSM call the module transmits in one timeslot, receives in one or two timeslots and is idle
for 5-6 timeslots. In all it transmits for 577µs and is idle or receiving for 4.03ms.
Taking worst case figures into account, this adds up to an average current consumption of about
500mA for 1Tx timeslot at GSM.