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AC75 Hardware Interface Description
Strictly confidential / Preliminary
3.3
Power-Up / Power-Down Scenarios
In general, be sure not to turn on AC75 while it is beyond the safety limits of voltage and
temperature stated in Chapter 4.1. AC75 would immediately switch off after having started
and detected these inappropriate conditions. In extreme cases this can cause permanent
damage to the module.
3.3.1 Turn on AC75
AC75 can be started in a variety of ways as described in the following sections:
•
Hardware driven start-up by IGT line: starts Normal mode or Airplane mode (see Section
3.3.1.1)
•
Software controlled reset by AT+CFUN command: starts Normal mode or Airplane mode
(see Section 3.3.1.4)
•
Hardware driven start-up by VCHARGE line: starts charging algorithm and charge-only
mode (see Section 3.3.1.3)
•
Wake-up from Power-down mode by using RTC interrupt: starts Airplane mode
The option whether to start into Normal mode or Airplane mode depends on the settings
made with the AT^SCFG command or AT+CALA. With AT+CALA, followed by AT^SMSO the
module can be configured to restart into Airplane mode at a scheduled alarm time. Switching
back and forth between Normal mode and Airplane mode is possible any time during
operation by using the AT^SCFG command.
After startup or mode change the following URCs indicate the module's ready state:
•
"SYSSTART" indicates that the module has entered Normal mode.
•
"^SYSSTART AIRPLANE MODE" indicates that the module has entered Airplane mode.
•
"^SYSSTART CHARGE ONLY MODE" indicates that the module has entered the
Charge-only mode.
These URCs are indicated only if the module is set to a fixed bit rate, i.e. they do not appear
if autobauding is enabled (AT+IPR≠0).
Detailed explanations on AT^SCFG, AT+CFUN, AT+CALA, Airplane mode and AT+IPR can
be found in [1].
3.3.1.1
Turn on AC75 Using Ignition Line IGT
When the AC75 module is in Power-down mode or Charge-only mode, it can be started to
Normal mode or Airplane mode by driving the IGT (ignition) line to ground. This must be
accomplished with an open drain/collector driver to avoid current flowing into this pin.
The module will start up when both of the following two conditions are met:
•
The supply voltage applied at BATT+ must be in the operating range.
•
The IGT line needs to be driven low for at least 400ms in Power-down mode or at least
1s in Charge-only mode. When released IGT goes high and causes the module to start.
Considering different strategies of host application design the figures below show two
approaches to meet this requirement: The example in Figure 5 assumes that IGT is activated
after BATT+ has already been applied. The example in Figure 6 assumes that IGT is held
low before BATT+ is switched on. In either case, to power on the module, ensure that low
state of IGT takes at least 400ms (Power-down mode) or 1s (Charge-only mode) from the
moment the voltage at BATT+ is available. For Charge-only mode see also Chapter 3.5.7.
AC75_HD_V00.202
Page 26 of 120
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27.04.2006
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