Monitoring Power Supply By At Command; Measuring The Supply Voltage; Batt; Figure 3: Power Supply Limits During Transmit Burst - Siemens AC75 Hardware Interface Description

AC75 Hardware Interface Description
Strictly confidential / Preliminary
Example: If the length of the flex cable reaches the maximum length of 100mm, this
connection may cause, for example, a resistance of 30mΩ in the BATT+ line and
30mΩ in the GND line. As a result, a 2A transmit burst would add up to a total
voltage drop of 120mV. 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 protection circuit.
3.2.2 Measuring the Supply Voltage V
The reference points for measuring the supply voltage V
GND, both accessible at a capacitor located close to the board-to-board connector of the
module.
Reference
point

BATT+

Figure 4: Position of the reference points BATT+ and GND

3.2.3 Monitoring Power Supply by AT Command

To monitor the supply voltage you can also use the AT^SBV command which returns the
value related to the reference points BATT+ and GND.
The module continuously measures the voltage at intervals depending on the operating
mode of the RF interface. The duration of measuring ranges from 0.5s in TALK/DATA mode
to 50s when AC75 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.
AC75_HD_V00.202

Figure 3: Power supply limits during transmit burst

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BATT+
on the module are BATT+ and
BATT+
Reference
point GND
s
27.04.2006