TLC770X Datasheet, PDF (7/27 Pages) Texas Instruments – BiCMOS SUPPLY VOLTAGE SUPERVISORS

Figure 2. Principle circuit of a Line (Mains) Power Supply C_res t = 0 and 0 < t₁ < T / 2 .
Figure 3. is intended to explain the relationship between the time of switch on and the voltages across the capacitor
and at the output of the line power supply.
Figure 3. Voltage waveforms in a line operated power supply a) Voltage waveform across the capacitor
C_Res when switched-on at a time t = 0 and 0 < t₁ < T / 2 . b) Voltage at the output when switched on at a time
0 < t₁ < T / 2 .
It can therefore take several cycles until the voltage has stabilized. With line power supplies, the switch-on process
has a typical duration of 10 - 20 ms: this means that the Reset signal must remain active at least for that period of
time.
The voltage monitoring circuit must keep the Reset signal active at least until the supply voltage has reached a
stable state.
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