Hi All,
My first question is:
1) What is the impedance from gate to cathode of an SCR/thyristor?
I ask because I want to use the SCR as a lowside switch/latch for power to a WDT. The gate of the SCR will be connected to the same pulse signal input to the WDT (from my microcontroller).
I want this because my WDT output is latched upon an error. And my microcontroller needs time to boot up and start the pulse. The time can vary and I want something to detect the pulse is live, and to then power up the WDT so it doesn't prematurely latch the output in an asserted state.
I put the led in parallel with the WDT to make sure there is sufficient holding current to keep the SCR on.
Take this SCR for example: https://media.digikey.com/pdf/Data Sheets/Littelfuse PDFs/TCR22-x_Sx02CSx_Series_DS.pdf
It need 5mA holding current. But then it says I_t is 200mA? Is that the latching current I need to go above to maintain anode to cathode current while gate is 0? That is a lot, I just saw that.
Can someone help me design this circuit. The WDT appears to pull like 10 uA. This is why I need something to help pull current to maintain the SCR in closed position. Also an LED would be a good debug indicator in this case i think.
Thank you!
My first question is:
1) What is the impedance from gate to cathode of an SCR/thyristor?
I ask because I want to use the SCR as a lowside switch/latch for power to a WDT. The gate of the SCR will be connected to the same pulse signal input to the WDT (from my microcontroller).
I want this because my WDT output is latched upon an error. And my microcontroller needs time to boot up and start the pulse. The time can vary and I want something to detect the pulse is live, and to then power up the WDT so it doesn't prematurely latch the output in an asserted state.
I put the led in parallel with the WDT to make sure there is sufficient holding current to keep the SCR on.
Take this SCR for example: https://media.digikey.com/pdf/Data Sheets/Littelfuse PDFs/TCR22-x_Sx02CSx_Series_DS.pdf
It need 5mA holding current. But then it says I_t is 200mA? Is that the latching current I need to go above to maintain anode to cathode current while gate is 0? That is a lot, I just saw that.
Can someone help me design this circuit. The WDT appears to pull like 10 uA. This is why I need something to help pull current to maintain the SCR in closed position. Also an LED would be a good debug indicator in this case i think.
Thank you!