TL331: function check

Hello Shu-Cheng,

The legal input voltage range is 0V to 2V below V+.

With a 5V supply, the legal input range is 0V to 3V. The values shown in the schematic are within legal range with a 5V supply.

With a 3.3V supply, the valid input range is 0 to 1.3V. The above values will still be within the legal range, though getting close at the upper end (1.2V vs 1.3V).

For #1 - The LMx93 and TL331 inputs can be taken up to 30V without damage, independent of V+. As long as the other input is within legal range, the output should be correct. But we do not recommend operation outside the specified input limits.

#2 - Yes.0.914V - remember to accommodate for comparator offset (±9mV) and any power supply variations and start-up sequencing.

#3 - Yes, it is possible with the conditions shown above.

#4 - Output will be "Hi" (3.3V) when PSYS_IC_OUT is <0.914V..  Output will be "Low" (<100mV) when PSYS_IC_OUT is >0.914V.

Hi Sirs,

Thanks for your reply.

As question 4, does TI have solution that the output is high when PSYS_IC_OUT is >0.914V??

Hi Sirs,

Thanks for your reply,

End customer request our add hysteresis resistor.

Do you have suggest value?

Thanks.

Hello Shu-Cheng,

How much hysteresis do they require?

The above schematic shows the hysteresis resistor going to the wrong input. It should go to the positive input pin 3 (since hysteresis is positive feedback).

Please see the LM339-N datasheet, and the attached document, on how to apply hysteresis.

/cfs-file/__key/communityserver-discussions-components-files/14/1411.Comparator_5F00_Hysteresis.pdf

Hi Sirs,

Thanks for your reply.

Double check TL331 design, I find our type like Figure24 from LM339-N datasheet.

But TL331 with LM139 is different IC, so please help to check our design again, many thanks.