I'm apology if the title is kinda generic but I found a (on a AC) which use IC and a triac and there is some points I don't really get.
Image from this application note:
Datasheet used as reference.
- About the PTA0 pin :
- How can the pin accept 120v since the range of the ADC is VSS to VDD (Page 161). The maximum absolute voltage for input is VSS-0.3 to VDD+0.3 which is far away from 120v, (Page 149)
- What about -120v? The PTA0 shouldn't have a diode to be a voltage above 0v?
- Why using resistors for the zero-crossing on the PTA0 pin? If it is to limit the current I tought input pin handled them.
- Z1 shouldn't do a shortcut when it reach the breakdown voltage from C1 to Ground? (C1 -> D2 -> Z1) (I assume the top graph is the positive side)
- I'm trying to know why it need 0.5W, I don't think it may be the IC (25mA maximum for PTA* pins, but I don't find the power consuption overall (50mA could be the overall consuptions (including PTA* output pin I hope) ?)
Also, there is an exemple using a generic opto coupler where they connect the anode to a 100k which then go to the AC :
- I know LED work with current instead of voltage... but i'm kinda surprise they work at 120v. Is it really possible or this is only true for opto coupler?
- Should -120v destroy the led since it is much more higher than the regular 5v reverse input voltage?