User's Manual

AC65/AC75 Hardware Interface Description
Confidential / Preliminary
s
AC65/AC75_hd_v00.372 Page 41 of 118 2006-08-03
The message will be reported, for example, when you attempt to make a call while the
voltage is close to the shutdown threshold of 3.2V and further power loss is caused during
the transmit burst. In IDLE mode, the shutdown threshold is the sum of the module’s
minimum supply voltage (3.2V) and the value of the maximum voltage drop resulting from
earlier calls. This means that in IDLE mode the actual shutdown threshold may be higher
than 3.2V. Therefore, to properly calculate the actual shutdown threshold application
manufacturers are advised to measure the maximum voltage drops that may occur during
transmit bursts.
To remind you that the battery needs to be charged soon, the URC appears several times
before the module switches off.
This type of URC does not need to be activated by the user. It will be output automatically
when fault conditions occur.
3.3.4.5 Undervoltage Shutdown if no Battery NTC is Present
The undervoltage protection is also effective in applications, where no NTC connects to the
BATT_TEMP terminal. Thus, you can take advantage of this feature even though the
application handles the charging process or AC65/AC75 is fed by a fixed supply voltage.
Whenever the supply voltage falls below the value of 3.2V the URC
^SBC: Undervoltage
appears several times before the module switches off.
This type of URC does not need to be activated by the user. It will be output automatically
when fault conditions occur.
3.3.4.6 Overvoltage Shutdown
The overvoltage shutdown threshold is 100mV above the maximum supply voltage V
BATT+
specified in Table 27.
When the supply voltage approaches the overvoltage shutdown threshold the module will
send the URC
^SBC: Overvoltage warning.
This alert is sent once.
When the overvoltage shutdown threshold is exceeded the module will send the URC
^SBC: Overvoltage shutdown,
before it shuts down cleanly.
This type of URC does not need to be activated by the user. It will be output automatically
when fault conditions occur.
Keep in mind that several AC65/AC75 components are directly linked to BATT+ and,
therefore, the supply voltage remains applied at major parts of AC65/AC75, even if the
module is switched off. Especially the power amplifier is very sensitive to high voltage and
might even be destroyed.