User's Manual

UE910 3G HARDWARE USER GUIDE 1vv0301171 Rev.3 • 2015-04-17 29 of 78

5.2 Power on

To turn on the UE910 the pad ON_OFF* must be tied low for at least 5 seconds and then released.

The maximum current that can be drained from the ON_OFF* pad is 0,1 mA.

A simple circuit to do it is:

NOTE:

Don't use any pull up resistor on the ON_OFF* line, it is internally pulled up.

Using pull up resistor may bring to latch up problems on the UE910 power

regulator and improper power on/off of the module. The line ON_OFF* must be

connected only in open collector or open drain configuration.

In this document all the lines that are inverted, hence have active low signals

are labelled with a name that ends with”#",”*” or with a bar over the name.

To check if the device has powered on, the hardware line PWRMON should be

monitored.

It is mandatory to avoid sending data to the serial ports during the first 200ms

of the module start-up.