eem2am
Banned
Hello,
I am doing an offline flyback with NCP1217 PWM controller.
NCP1217 DATASHEET:
https://www.onsemi.com/pub_link/Collateral/NCP1217-D.PDF
(block diagram is on page 3)
...I wish to incorporate Overvoltage protection using a PNP as on page 13.
However, on page 13 it says that the current injected into pin 1 should be kept less than 2mA when using a 10V rail voltage.
....they thus suggest using a 5K6 resistor to limit the current into pin 1.
...the thing is, pin 1 already has a 24K resistor to ground, so even without the
5K6 limiting resistor, it is not possible to get the current above 2mA anyway.....
...therefore, i cannot understand why on page 13 they speak of using a 5K6 resistor.
Do you know why they suggest using a 5K6 resistor on page 13?
I am doing an offline flyback with NCP1217 PWM controller.
NCP1217 DATASHEET:
https://www.onsemi.com/pub_link/Collateral/NCP1217-D.PDF
(block diagram is on page 3)
...I wish to incorporate Overvoltage protection using a PNP as on page 13.
However, on page 13 it says that the current injected into pin 1 should be kept less than 2mA when using a 10V rail voltage.
....they thus suggest using a 5K6 resistor to limit the current into pin 1.
...the thing is, pin 1 already has a 24K resistor to ground, so even without the
5K6 limiting resistor, it is not possible to get the current above 2mA anyway.....
...therefore, i cannot understand why on page 13 they speak of using a 5K6 resistor.
Do you know why they suggest using a 5K6 resistor on page 13?