Comparator with hysteresis

comparator hysteresis

Hello, I am using the on-chip comparator on PIC12F675 microcontroller.

I want to use hysteresis but i have no access to the non-inverting pin (since its got an internal reference voltage on it)

Can i do hysteresis by putting a resistor between comparator output and its inverting input?

Many thanks for reading.

comparator with hysteresis

No, but you can add simple digital inverter to comparator output and inverter output to connect to inverting comparator input through resistor.This is hysteresis because feedback will be positive in this case.

hysteresis comparator

eem2am,
I have not used this microcontroller. However the data sheet implies that you have some options for implementing hysteresis. You indicate that you have the comparator configured with the NI input connected to an internal reference. If the comparator is configured as a non inverting comparator (control register bit 4 = 0), then feeding the output back to the inverting input won't work, because this would be negative feedback (you need positive feedback.)
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One option is to configure the comparator as an inverting comparator (control register bit 4 = 1). Then you can feed the output back to the inverting input through a resistor and get positive feedback. However, the input signal must be connected to the inverting input through a resistor. The ratio of the two resistors will determine the amount of hysteresis.
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If you can not use the inverting comparator configuration, then you have another (more complicated) option. Invert the comparator output using an external hardware logic inverter. Connect the output of the external inverter to the inverting input through a resistor, as described above.
Regards,
Kral