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User Manual May 2019 | Page 30/49
USER MANUAL
Scavenger Transmitter Module
STM 330 / STM 331 STM 331U / STM 332U / STM 333U
(Stepcode DE and later)
3.13
Charging circuitry
The figure below shows the internal charging circuit. It is controlled via the WXODIO pin of
EO3000I which switches according to the status of the internal threshold detector. For de-
tails please refer to our Dolphin Core Description documentation. The WXIDIO pin is used to
disconnect the long term energy storage at voltages below VOFF to avoid deep discharge.
An external 3 V backup battery can be connected at VCHAR. If STM 3xy is battery supplied,
we strongly recommend to avoid keybouncing by adding a PI filter at wake inputs with but-
tons or keys (details see below).