Cinterion
®
ELS31-VA/ELS51-VA Hardware Interface Description
3.2 Power Up/Power Down Scenarios
76
ELS31-VA_ELS51-VA_HID_v01.000
2017-01-04
Confidential / Preliminary
Page 59 of 106
3.2.1.2
Switch on ELS31-VA/ELS51-VA Using ON Signal
When the operating voltage BATT_BB is applied, ELS31-VA/ELS51-VA can be switched on by
means of the ON signal.
The ON signal is an edge triggered signal. The module starts into normal mode on detecting a
rising edge at the ON signal. The subsequent high level at the ON signal should last for at least
100µs. Note that if the ON signal is set to high before BATT_BB is applied, ELS31-VA/ELS51-
VA may not start up correctly.
Figure 32:
ON timing
The module can also start automatically and immediately after applying the VBATT by connect-
ing the ON pad to BATT_BB for a so-called auto start mode. If ON is connected to BATT_BB,
and the module is switched off (e.g. by calling AT^SMSO), it will immediately restart.
For the auto start mode, it is recommended to set a pull-up resistor of maximum TBD.kOhm
between the ON circuit and the BATT_BB power supply.
Note:
If during a power cycle or voltage drop the BATT_BB voltage level does not drop below
0.5V, it may happen that the module can no longer start up properly, because its reset condition
was not reached. This scenario can happen, if the BATT_BB supply is decoupled by big capac-
itors – with a slow discharge after a sudden power drop. So, please make sure to keep the pow-
er off state long enough for the capacitors to discharge below 0.5V. As a workaround it is
recommended to reset the module with EMERG_RST after startup (see also
If an automatic module startup is configured for the module, i.e., the ON signal is connected to
BATT_BB, then the EMERG_RST signal may be generated automatically – using an external
voltage detector - when the BATT_BB voltage does reach the valid operating voltage range.
BATT_BB
ON
V180
VCORE
> 250µs
> 250µs
EMERG_RST
High level 100µs min.
~ 100ms