TLV7031: TLV7031 Output is incorrect

Hi Weifeng,

what are you complaining? The output voltage of simulation or of your circuit?

Kai

Hi，Kai

I use the same circuit in my test PCB.And Ve=845mV,  Va=750mv，but the output of comparator is 0.8V to 1V.

I don't no why the output isn't 0V?

Is it possible that 10M ohms is too big?

There is nothing wrong with my circuit?

Hi Weifeng,

well the circuit isn't wrong but it's not optimal either. It could oscillate which might exactly look like a wrong output voltage when measuring with a DC multimeter.

I guess that decreasing the resistances is no option because you want to save supply current? Then I would make the circuit more robust by filtering, shielding and adding hysteresis:

Add a cap from input "E" to ground. Add a cap from point "5" or point "8" to ground. Remove C2 and C3. Connect a very high resistor (1...10G) from point "4" to point "Out". This will add hysteresis to the comparator. If this does not help enough, try to shield the circuit by a piece of metal which you connect to signal ground. A solid ground plane in an inner layer or on the bottom side of PCB can help a lot.

By the way, what load are you connecting to the output of TLV7031?

Kai

Hi,Kai

1.I want to save supply current so choose 10M ohms.

2. The output of TLV7031 is without any load,and it connect to MCU

3.If connect a very high resistor (1...10G) from point "4" to point "Out",the Vhys will be  ?mV

Thanks

Hi Weifeng,

you can simulate it :-)

Or do you want to share your TSC-file?

Kai

Weifeng,

The current model on the web has some bugs in it, and is in the process of being republished for web use.

Please try out this model and let me know if you have any additional concerns.

Thanks,

Jonny

8688.TLV7031.TSC

Hi Kai

I want  to do your suggestion,but I don't have 1G resistor.so i use 20M to change 1G,but the output is still 0.8V~1V.and I use tina to simulate calculation,and tina display errors. Do you have any other suggestion?

I share you my TSC-File.

By the way,can you speak chinese?

Thanks a lot.TLV7031_0703.TSC

Hi Jonny

I will try your model.Thanks

Weifeng

we will await your results.

Chuck

Hi Weifeng,

I would give this circuit a try:

weifeng_tlv7031.TSC

The TLV7031 has a built-in hysteresis. Maybe it provides sufficient hysteresis and an external resistor can be omitted.

C2 is filtering the voltage at the -input of TLV7031. R7 limits the input current. R7 can be helpful, if you need to increase C2.

Kai

PS: Unfortunately, I cannot speak Chinese :-)