d123
Advanced Member level 5
Hi,
To implement an RC low pass filter at a (window) comparator input that is buffered by a voltage follower op amp, the window comparator purpose is to control an LDO enable pin and only take it high between 0C and +45C, what might be a realistic RC LPF value to avoid comparator chatter if hysteresis isn't used?
Would ~3.3 Hz (0.29s) be okay/suitable to filter out fluctuations around the trigger points? Let's say the temperature sensor is in still air.
The simulation showed it to be effective but maybe ambient temperature fluctuates faster or slower than my guess.
Attached is the schematic, the upper buffer, difference amplifier and comparator are sort of not important to this question as it's the lower buffer and window comparator the transient results were taken from.
FWIW, the transient shows fast fluctuation at first where the LPF seems effective at filtering out spurious, momentary rise and fall around the upper trigger point and then a longer rise over +45C where the window comparator triggers as required.
Also, can I feed one LPF into both buffers or is it wiser to use one for each?
Thanks.
To implement an RC low pass filter at a (window) comparator input that is buffered by a voltage follower op amp, the window comparator purpose is to control an LDO enable pin and only take it high between 0C and +45C, what might be a realistic RC LPF value to avoid comparator chatter if hysteresis isn't used?
Would ~3.3 Hz (0.29s) be okay/suitable to filter out fluctuations around the trigger points? Let's say the temperature sensor is in still air.
The simulation showed it to be effective but maybe ambient temperature fluctuates faster or slower than my guess.
Attached is the schematic, the upper buffer, difference amplifier and comparator are sort of not important to this question as it's the lower buffer and window comparator the transient results were taken from.
FWIW, the transient shows fast fluctuation at first where the LPF seems effective at filtering out spurious, momentary rise and fall around the upper trigger point and then a longer rise over +45C where the window comparator triggers as required.
Also, can I feed one LPF into both buffers or is it wiser to use one for each?
Thanks.