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Seeking very slow comparator

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treez

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Hello,
This comparator (MCP65R46T) has a propogation delay of 4us.
https://ww1.microchip.com/downloads/en/DeviceDoc/22269B.pdf

Are there any comparators which have a longer delay than this, say about 100us? –Its just that I don’t want it to trip errantly on noise as it will shut the equipment down when it trips…I want it to trip very slowly.
 

treez

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I see your point, connected the opposite way to hysteresis components...ie..negative feedback
 

Gorgon

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Also called a Schmitt-trigger design, with a positive feedback on the noninverting input.
 
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Audioguru

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A comparator cannot use negative feedback because it does not have the frequency compensation capacitor used in an opamp. A comparator will oscillate at a high frequency when it has negative feedback.
The comparator is supposed to switch its output high or low very quickly. Hysteresis is used to make it switch even faster and avoid oscillating when its input voltages are almost the same.
To reduce it from detecting noise then use an RC lowpass filter on its input.
 
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KlausST

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Hi,

yes, i also tend to low pass filter. Either as mentioned before an simple RC, or if you are using a uController, then you can use software lowpass.
(with keys this is often called "debouncing")

Klaus
 
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Dominik Przyborowski

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Use high value pull-up resistor and load its output with capacitor. For 5V vdd, 100 kΩ pull-up resistor and 5nF capacitor You should obtain response with 10V/ms slew rate. Now You need only to follow comparator by any inverter to get sharp response delayed around 100µs.
 
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