Dc Power Supply Interface; Battery Power Input, Vbat; Boost Power Input, Vboost; Power On/Off Control, Trx_On - Iridium 9523 Product Developer Manual

Iridium Communications, Inc.
Iridium 9523 Product Developer's Guide
Revision 7.0
Output High Voltage
Output Low Voltage
Low Level Output Current
High Level Output Current

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, command AT*P0 should be issued to ensure all memory write activity is
completed.
When the 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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