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Integrating GSP-1620 Modems into OEM Products
80-99208-1 Rev. D 7-15
DC Power
The GSP-1620 modem requires input DC power ranging from
5.6 V to 16 V, with 1 Amp (maximum). The modem DC input
power must be clean (maximum of 50 mV peak-peak ripple
and noise) and must be within the absolute maximum voltage
range of 5.6 V to 16 V under all conditions. For typical DC
power consumption limits, see Power Consumption on page
7-16.
The GSP-1620 modem uses a DC/DC converter to source its
internal operating voltages and behaves like a constant
power load over varying input voltages that has a varying
input impedance when the modem is transmitting data. This
creates a potential for oscillations on the DC power line if the
input impedance of the modem is lower than that of the power
supply sourcing the power.
The approximate minimum input impedance of the modem is
given by R = V
2
/P
max
where V is the operating voltage of the
modem and P
max
is the maximum power consumed by the
modem. For example, the minimum input impedance of the
modem at 12V would be approximately 12*12/5.4 = 26.7
Ohms. Any DC power supply capable of supplying the peak
demand of 5.4W at 12V would have this output impedance.
Additional design margin of at least 20% is recommended
beyond this minimum value.
Care should be taken that if additional EMI filtering is added
(see EMI Filtering on page 7-16), the impedance as seen by
the modem’s input power supply does not exceed this value.
Warning
Do not unplug the power cables while the modem is powered up.
This can cause ESD damage to the modem and also presents a
danger of electrical shock.
Caution
You must ensure that the output impedance of the power supply
sourcing DC power to the modem is always less than that of the input
impedance of the modem. Otherwise, a potential exists for oscillations
on the DC power line and the GSP-1620 modem will not operate as
designed.