RIM 1802G, Integrator Manual

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Chapter 5: Power requirements
46 RIM OEM Radio Modem for GSM/GPRS Wireless Networks
Load specifications
The RIM 1902G or RIM 1802G draw their power in bursts; the power required changes rapidly
depending on whether the radio is transmitting, receiving, or idle.
Power supply parameters
The RIM 1902G or RIM 1802G requires a clean, stable 3.5 to 4.75 volt source that is capable of
delivering a 577us burst every 4.616 ms of up to 1.2 A (for the RIM 1902G) or 2.0 A (for the RIM
1802G) when it is required by the transmitter. RIM recommends that you design a more robust
power supply that can provide adequate power under such non-ideal conditions as an improperly
matched antenna, under which this burst could be as high as 2.2 A.
If you want your RIM GPRS hardware integration to be compatible with the RIM 902M™ and RIM
802D™ radio modems, make sure that the power input to the radio modem is above 4.1 V. Contact
the RIM OEM Integration Specialist team for further details on backwards compatibility.
Ripple specification
For best performance, RIM recommends a ripple of less than 15 mV peak-to-peak (measured at the
radio end of the connector) across the frequency range 60 Hz to 1 MHz. The maximum ripple at the
connector that can be tolerated is 20 mV peak-to-peak.
Except in special cases where there are several sources of ripple, you should measure the ripple with
an oscilloscope set to 1-MHz bandwidth; the peak-to-peak value is not to exceed 15 mV.
You can place a passive LC (series L, shunt C) power filter between your power supply and the RIM
radio modem to reduce ripple at the radio connector. The radio modem already has approximately
70
µ
F of on-board shunt capacity. The inductor cannot exceed 100
µ
H (otherwise, transients could
reset the radio), it must be rated to pass the maximum DC current of 2.2 A supply current at all
temperatures, and its resistance must be low enough to guarantee minimum voltage of 3.5V to the
radio modem at 2.2 A.
Note: If there are several ripple components, or if the ripple is measured with a larger (typically 20-MHz)
bandwidth, the ripple appears to be worse than it is. If the ripple is still below 15 mV under these conditions, it
meets the ripple specification.