User's Manual
Iridium Communications, Inc. Information Contained in this Guide
Iridium Core 9523/9523N Product Developer’s Guide is Subject to Change Without Notice
Revision 7.2 DRAFT4
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3.2.2 Power On/Off Control, TRX_ON
The input signal TRX_ON is provided to allow the Iridium Core 9523/9523N to be powered off. This signal
controls the power regulators on the Iridium Core 9523/9523N.
The Iridium Core 9523/9523N starts up when power is applied and the TRX_ON input is high. As long as
the input voltage is applied, logic high on this line turns the Iridium Core 9523/9523N on and a logic low
turns it off. If this line is not required then it must be connected directly to the VBAT supply.
Prior to turning off the modem, command AT*P0 should be issued to ensure all memory write activity is
completed.
When the Iridium Core 9523/9523N is powered off, the power-on-reset circuit requires 2 seconds for
voltages to decay. Product Developers should therefore not reapply power until this time has elapsed
after power has reached 0V. If the 2 second wait time is not adhered to, the reset circuit may not operate
and the modem could be placed in a non-operational state. The state is not permanent and can be
rectified by the above procedure.
Damage may be caused if TRX_ON is high and VBAT is not supplied. Partners must ensure that this
condition cannot occur either by generating TRX_ON from VBAT or by adding protection circuitry such as
a clamp diode between TRX_ON and VBAT.
3.2.3 Typical Power Usage Profile
The amount of current taken by the Iridium Core 9523/9523N on its two supply rails depends on whether
it is active in a call and the ‘power step’ level that the transmitter is using. The current consumption during
a call at the highest power step is shown in Figure 8.
Figure 8: Current Profile of Supply Rails
I/mA
100
200
300
400
500
600
700
800
900
1000
10 20 30 40 50 60 70 80 90 100
t/ms
Current in VBOOST Rail
Current in VBAT Rail