The presentation will now take a look at how 1-Wire devices operate on parasitic power. An internal capacitor and circuit equivalent to a half-bridge rectifier provide the parasitic power circuitry. When the line is idle (high) the diode is forward biased and charges the internal capacitor. When the line is low, the stored charge provides energy to power the internal oscillator and control circuitry (Vdd). Charge lost during these time slots is replenished when the data line returns to the logic 1 (high) state.