Iridium Communications, Inc. Information Contained in this Guide
Iridium 9523 Product Developers’ Guide is Subject to Change Without Notice
Revision 2.6
Iridium Communications, Inc. Distribution of Guide Restricted
Proprietary & Confidential Information Page 22 of 115 to Product Developers
Only
Output Low Voltage V
OL
0.4 V
Low Level Output Current I
OL
4.4 mA
High Level Output Current I
OH
5.5 mA
3.2 DC Power Supply Interface
3.2.1 Battery Power Input, VBAT
VBAT is the input from a Lithium-ion battery or other low-voltage source via the user connector. It must be
in the range 3.2 to 6V and capable of supplying a maximum current of 500mA.
3.2.2 Boost Power Input, VBOOST
VBOOST - Boost converter input via user connector. See Section 3.2.4 for details.
The Iridium 9523 produces the logic signal PA_BOOST_EN to indicate when the external Boost Power
voltage must be applied. This signal can be used as the enable signal to an external boost regulator (logic
high = VBOOST needed, logic low = VBOOST not needed).
3.2.3 Power On/Off Control, TRX_ON
The input signal TRX_ON is provided to allow the Iridium 9523 to be powered off. This signal controls the
power regulators on the Iridium 9523.
The Iridium 9523 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 9523 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 a “flush memory” (AT*F) command should be issued to ensure all memory
write activity is completed.
When an Iridium 9523 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.
3.2.4 Typical Power Usage Profile
The amount of current taken by the Iridium 9523 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 7.
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