Hi crutschow
We hadn’t tested the circuit you provided until now. Other things got in the way, but we are ready to try to get this SENT thing going, and I think this balanced front end is required based on the sketchy description provided by Renesas.
Anyway, it turns out the circuit behaves as expected, with 2.54V on both outputs with zero in, and 2.5 V spread at 5V in. To get the delta between outputs at zero input, I changed R1 to 10K (from 10.2). That could be because of component tolerance. I want to thank you again for providing the solution that I would never have come up with!
Whether we can get the ZSSC416x working is another challenge…
David Cyr

 

Below is the sim of circuit using two op amps (one package, inexpensive) with rail-rail outputs that gives a differential output centered at +2.5V:
The outputs go from +2.5V to +3.75V (yellow trace) and +1.25V (red trace) for an input of 0V to 5V (X-axis).
The differential output (difference between the two outputs - green trace) thus goes from 0V to 2.5V.

The 2.5V output offset value does depend upon the value of the 5V supply (varies by 1/2 the 5V change), but that doesn't affect the differential output voltage (differential gain), which is determined by the resistor ratios.

The output bandwidth should be over 500kHz.

Is that satisfactory for your purposes?

View attachment 300705

The circuit will work for some range, but most opamps are not perfectly accurate as the output voltahe approaches either of the supply voltages. That is seldom a problem in simulations, but in the real world it is quite inconvenient.

 

It is absolutely perfect. I just wanted to let you know that we breadboarded your circuit and it does exactly what we need as input to the 2-channel ZSSC4165D. We will have two analog inputs (two of your circuits) with one SENT message going to the car's ECU.
THANK YOU!!!

 

David;
It is always refreshing that someone who has received assistance, to thank the person which provided the support.
It speaks highly of you.

 

Thanks for letting me know that it worked well.
A little "attaboy" every now and then keeps me posting on this site.

 

The circuit will work for some range, but most opamps are not perfectly accurate as the output voltahe approaches either of the supply voltages.

This circuit output limits are, 1.25V and 3.75V from a 5V supply, so not close to the rails.

 

The circuit will work for some range, but most opamps are not perfectly accurate as the output voltage approaches either of the supply voltages. That is seldom a problem in simulations, but in the real world it is quite inconvenient.

This circuit works rail-to-rail on input, which is what we want, and the output appears to be linear across the range of input going from 0 - 5V. The output doesn't go close to the rails, and it simulates a Wheatstone bridge that the ZSSC416x expects. It is brilliant!!!

 

OK, you are not trying to use it where it will have problems!

 

OK, you are not trying to use it where it will have problems!

Not sure what your concern is. We use only AEC-Q100 components that get potted, so we couldn't improve reliability unless we have 3 parallel systems to get the best 2 out of 3.

 

Not sure what your concern is. We use only AEC-Q100 components that get potted, so we couldn't improve reliability unless we have 3 parallel systems to get the best 2 out of 3.

My concern is that for most OP-Amps, the accuracy is less when the output voltage is very close to the supply voltage. Based on your posts, that is not part of your application. You have avoided the problem very well, because the output voltage in this application does not approach the supply voltages.