User's Manual

USER MANUAL 1.34

STM 300 / STM 300C / STM 300U

4.2 Using the SCO pin

STM 300 provides an output signal at SCO which is suited to control the supply of the sen-

sor circuitry. This helps saving energy as the sensor circuitry is only powered as long as

necessary. In the default configuration SCO provides a HIGH signal 2 ms (delay time) be-

fore the analog inputs are read. Via the programming interface (see 3.8.2) it is possible to

adjust the delay time and also the polarity of the signal.

The figure above shows, how the SCO pin (with default polarity) can be used to control an

external sensor circuit.

Do not supply sensors directly from SCO as this output can only provide maximum

15 µA!

4.3 Using the WAKE pins

The logic input circuits of the WAKE0 and WAKE1 pins are supplied by UVDD and therefore

also usable in “Deep Sleep Mode” or “Flywheel Sleep Mode” (via API only). Due to current

minimization there is no internal pull-up or pull-down at the WAKE pins.

When STM 300 is in “Deep Sleep Mode” or “Flywheel Sleep Mode” (via API only) and the

logic levels of WAKE0 and / or WAKE1 is changed, STM 300 starts up.

As the there is no internal pull-up or pull-down at the WAKE pins, it has to be en-

sured by external circuitry, that the WAKE pins are at a defined logic level at any

time.

When using the UVDD regulator output as source for the logic HIGH of the WAKE

pins, it is strongly recommended to protect the ultra low power UVDD voltage

regulator against (accidental) excessive loading by connection of an external

1.8 MΩ series resistor.