Other Parts Discussed in Thread: LM331, LM393
Hello anyone,
I ran into a problem by using the LMV331, it seems, the function of this IC is not like descripted in the Datasheet:
I constructed a circuit with LMV331, which is working well.
LM331 has a pull-Up resistor at the output.
If In+ is higher than In- the output transistor is not active and the external pullup resistor pulls the output upwards.
So a positive input difference gives a positive output.
If I look in the datasheet of the LMV331: SLCS136T–AUGUST1999–REVISED JANUARY2015
I can read at point 8.3:
The output consists of an open drain NPN (pull-downorlowside) transistor. The output NPN willsink current
when the positive inputvoltage is higher than the negative inputvoltage and theoffsetvoltage.The VOL is
resistive and will scale with the outputcurrent...
I noticed: ... will sink current means, the transistor will switch on if the difference is positive (In+ higher than In-)
But that is not what my circuit does?!
Now I decided to look into the LM393 datasheet, because it seems to me the LMV331 and the LM393 are of the same type.
LM393 Datasheet: SNOSBJ6G–OCTOBER1999–REVISED OCTOBER2018
In this datasheet i found at point 7.4:
...The output is HIGH when the voltage on the non-inverting (+IN) input is greater than the inverting (-IN) input. The output is LOW when the
voltage on the non-inverting (+IN) input is less than the inverting (-IN) input...
So, that is exactly the way my Circuit with LMV331 is working.
Ok, I get on to the next pages in LM393 datasheet and found this curve in the applications section:
8.2.1.3 Application Curve
At point 8.2.1.2 the connections of LM393 are described in detail.
The most interesting description is about input connection:
...With a100-kΩ resistor from IN– to V+ and an additional
100-KΩ resistor from IN–to ground...
So In- is connected to a reference an In+ may be the input. in the above plot.
Output of LM393 is connected to a pullup-resistor as usual.
In my opinion the plot above shows the output signal in an inverted form.
Now I'm completely confused. What is there going on in these datasheets? Or am I completely wrong in understanding the function of the output?
Can You please have a look into the datasheet and help me understanding the meaning of the Descriptions?
Thank You very much
- pleas excuse my bad English, I'm a German user...
Dirk
