Gemalto M2M GmbH MC56 User Manual
MC55/56 Hardware Interface Description
Confidential / Preliminary
Confidential / Preliminary
s
MC55/56_hd_v03.00
Page 26 of 104
16.08.2005
3.2.2
Minimizing power losses
When designing the power supply for your application please pay specific attention to power
losses. Ensure that the input voltage V
losses. Ensure that the input voltage V
BATT+
never drops below 3.3V on the MC55/56 board,
not even in a transmit burst where current consumption can rise to typical peaks of 1.6A. It
should be noted that MC55/56 switches off when exceeding these limits. Any voltage drops
that may occur in a transmit burst should not exceed 400mV. For further details see Chapter
5.4.
The best approach to reducing voltage drops is to use a board-to-board connection as
recommended, and a low impedance power source. The resistance of the power supply lines
on the host board and of a battery pack should also be considered.
should be noted that MC55/56 switches off when exceeding these limits. Any voltage drops
that may occur in a transmit burst should not exceed 400mV. For further details see Chapter
5.4.
The best approach to reducing voltage drops is to use a board-to-board connection as
recommended, and a low impedance power source. The resistance of the power supply lines
on the host board and of a battery pack should also be considered.
Note:
If the application design requires an adapter cable between both board-to-board
connectors, use a cable as short as possible in order to minimize power losses.
connectors, use a cable as short as possible in order to minimize power losses.
Example: If the length of the cable reaches the maximum length of 200mm, this connection
may cause, for example, a resistance of 50mΩ in the BATT+ line and 50mΩ in
the GND line. As a result, a 1.6A transmit burst would add up to a total voltage
drop of 160mV. Plus, if a battery pack is involved, further losses may occur due
to the resistance across the battery lines and the internal resistance of the battery
including its protective circuit.
the GND line. As a result, a 1.6A transmit burst would add up to a total voltage
drop of 160mV. Plus, if a battery pack is involved, further losses may occur due
to the resistance across the battery lines and the internal resistance of the battery
including its protective circuit.
Transmit
burst 1.6A
Transmit
burst 1.6A
Ripple
Drop
min. 3.3V
BATT+
Figure 2: Power supply limits during transmit burst
The input voltage V
BATT+
must be measured directly at the test points on the MC55/56 board
3.2.3
Monitoring power supply
To help you monitor the supply voltage you can use the AT^SBV command which returns the
voltage measured at TP BATT+ and GND.
The voltage is continuously measured at intervals depending on the operating mode on the
RF interface. The duration of measuring ranges from 0.5s in TALK/DATA mode up to 50s
when MC55/56 is in IDLE mode or Limited Service (deregistered). The displayed voltage (in
mV) is averaged over the last measuring period before the AT^SBV command was executed.
For details please refer to [1].
voltage measured at TP BATT+ and GND.
The voltage is continuously measured at intervals depending on the operating mode on the
RF interface. The duration of measuring ranges from 0.5s in TALK/DATA mode up to 50s
when MC55/56 is in IDLE mode or Limited Service (deregistered). The displayed voltage (in
mV) is averaged over the last measuring period before the AT^SBV command was executed.
For details please refer to [1].