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 30 of 70
An example of switching regulator with 12V input is in the schematic below:
5.2.4. Battery Source Power Supply Design
Guidelines
The desired nominal output for the power supply is 3.8V and the maximum voltage allowed is
4.2V. A single 3.7V lithium-ion cell battery type is ideal to supply power to the Telit DE921
module.
WARNING:
The three battery cells (Ni/Cd or Ni/MH 3.6V nom. battery types or 4V PB types) MUST
NOT be used directly because their maximum voltage can rise over the absolute maximum
voltage for the DE921 and cause damage. USE only Li-Ion battery types.
 A bypass low (usually a 100uF tantalum) ESR capacitor with adequate capacity
must be provided in order to cut the current absorption peaks.
 Make sure the low ESR capacitor (usually a tantalum) is rated at least 10V.
 A protection diode must be inserted close to the power input in order to protect
the DE921 module from power polarity inversions when connecting the battery.
 The battery capacity must be at least 500mAh in order to withstand the current
peaks of 1A. The suggested battery capacity is from 500mAh to 1000mAh.