TLC27L4: Problem with TLC27L4

Hello edsonemboaba,

Do you have information printed on the the reel packaging?

Trimming both ends will help eliminate linear errors in Vos, CMRR and AVD. As VCM and VOUT change the result is not always a straight line (nonlinearities). As current changes from 4mA to 20mA, how much does op amp's VCM, Vout and Iout change (or provide a schematic)?

10uA is only 0.08% error and the minimum CMRR and AVD allow for a lot of variance.  There may be much better alternatives today.

Can you provide two example tables that show output current versus input setting.

hi Ron 

I know that 10uA is 0.08%, but it is too much for my application, normaly a have  less than 0.01% and the precision of my intire  transmitter is  less than 0.025% . I use TLC27L4 in all my products and I never had problem,  it is the first time that I have this error in current liniarity. 

"There may be much better alternatives today " - I know that,  but the cost of TLC27L4 is best  compared with others.

Regards

Edson,

What are the key parameters needed? I can do another search for you.

I'm glad the the linearity of TCL27L4 had a 10 year good run in your application. Linearity is not a direct specification. Closely related parameters are Avd and CMRR, so having high minimum limits is a lower risk way to achieve the goal.

I didn't see any any product changes, so this may be just one group of devices where the risk of not having data sheet better specs didn't work out.

Hi Ron!

I'm sorry maybe   I wasn't clear about linearity, When talk about linearity,I mean that the output current from my  transmitter has almost zero error, 
But with some TLC27L4 that I dont why,  the error is 0.08%. I know that problem is caused by TLC27L4 because a change the IC and the error
goes to about 0%. And this output circuit I am using without change for long time.The TLC27L4 is working but not fine as it should be working. And know TLC27L4 it is good OP/AMP.
 Maybe some parameters is out specification for I don´t know why  or could a problem with handling. I just wrote here to know if you have any idea
 what could be happening, or if you have any comment about problem in lot of TLC27L4.

Regards

Edson,

As I understand, there is a correction circuit that adds some corrective factor so 4mA and 20mA points are correct. I'm curious (but don't have to know) if this a 'one and done' correction? Do you have data to show that temperature and component aging do not drift?

If you have some data that shows that a specification with a limit is failing then I can do more. I don't have a schematic or know how much Vcm, Vout, Iout, and Vos changes across the span in the application. 

Input_circuit.pdf

This is the circuit that I use TLC27L4. It is old circuit , but works fine.

Regards

Edson,

The circuit is very helpful for me. Please check pin 1 on oscilloscope with FET (or 10X) probe (low capacitance) on AC coupling and check for oscillation or any other noise. Also tell me the ripple voltage and frequency on pin 10.

Hi

I discover that the problem with this TLC27L4 is when it is using  in voltage follower or  voltage buffer. We have error in output of this voltage follower I change for a old one or for a ST similar component and the  circuit works. But just happining in this lot of component. 

Regards

Hi

I discover that the problem with this TLC27L4 is when it is using  in voltage follower or  voltage buffer. We have error in output of this voltage follower I change for a old one or for a ST similar component and the  circuit works. But just happining in this lot of component. 

Regards

Edson,

I see. Make sure the ST replacement has high minimum specification for CMRR. This won't ensure the CMRR over the application range will only have first order (linear) curve shape. A good spec make linearity more likely. If its spec isn't good, then you may encounter the same issue later.