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9 - A Carrier-current System for domestIc Remote Control
same time, this produces a voltage drop of about 1 V across the capacitor. The ST72251 al-
lows a comfortable range of power supply voltages, so that the drop is acceptable.
The ST7 will also be used in an economical manner. For this reason, it is clocked by a 1 MHz
crystal, that provides an internal clock of 500 kHz. Being a CMOS device, the ST7 has a con-
sumption roughly proportional to its main clock frequency. Reducing the frequency will there-
fore reduce the current drawn.
In addition, the Analog to Digital converter is only powered when needed, and the core is set
to wait state whenever it has nothing to do but wait. The power is reduced in this state.
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