User's Manual

DE910 Series Hardware User Guide
1vv0301183 Rev.1 – 2015-2-13
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved. Page 20 of 70
4. Hardware Commands
4.1. Turning on the DE921 module
To turn on the DE921, the pad ON_OFF* must be tied low for at least 1 second and then
released.
The maximum current that can be drained from the ON_OFF* pad is 0.1 mA.
A simple circuit to power on the module is illustrated below:
4.1.1. Initialization and Activation State
Upon turning on DE921 module, the DE921 module is not active yet because the boot
sequence of DE921 is still executing internally. It takes about 10 seconds to complete the
initialization of the module internally.
For this reason, it would be useless to try to access DE921 during the Initialization state as
below. The DE921 module needs at least 10 seconds after the PWRMON goes High to
become operational by reaching the activation state.