User's Manual

AC65/AC75 Hardware Interface Description

Confidential / Preliminary

AC65/AC75_hd_v00.372 Page 27 of 118 2006-08-03

Example: If the length of the flex cable reaches the maximum length of 100mm, this

connection may cause, for example, a resistance of 30m in the BATT+ line and

30m 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.

Figure 3: Power supply limits during transmit burst

3.2.2 Measuring the Supply Voltage V

BATT+

The reference points for measuring the supply voltage V

BATT+

on the module are BATT+ and

GND, both accessible at a capacitor located close to the board-to-board connector of the

module.

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 AC65/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.

Reference

point

BATT+

Reference

point GND