HE920 Hardware User Guide
1vv0301014 Rev.9 – 2014-01-23
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
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Page 38 of 84
5.2.1.3.
Battery Source Power Supply Design Guidelines
The desired nominal output for the power supply is 3.8V and the maximum
allowed voltage is 4.2V, hence a single 3.7V Li-Ion cell battery type is suited for
supplying the power to the Telit HE920 module. The three cells Ni/Cd or Ni/MH
3.6 V Nom. battery types or 4V PB types must not be used directly since their
maximum voltage can rise over the absolute maximum voltage for HE920 and
damage it.
NOTE:
Do not use any Ni-Cd, Ni-MH, and Pb battery types directly connected with HE920. Their
use can lead to overvoltage on HE920 and damage it. Use only Li-Ion battery types.
A Bypass low ESR capacitor of adequate capacity must be provided in order to
cut the current absorption peaks, a 100μF tantalum capacitor is usually suited.
Make sure the low ESR capacitor (usually a tantalum one) is rated at least 10V.
A protection diode must be inserted close to the power input, in order to save
HE920 from power polarity inversion. Otherwise the battery connector must be
done in a way to avoid polarity inversions when connecting the battery.
The battery capacity must be at least 500mAh in order to withstand the current
peaks of 2A; the suggested capacity is from 500mAh to 1000mAh.
