What you always wanted to know about TINA-TI but were afraid to ask! (Part 1)

Other Parts Discussed in Post: TINA-TI, LMH6553

There is a lot you can do with TINA-TI; more than is obvious at first glance. This free electrical simulation software from TI is capable of unlimited nodes, it already has most of TI devices built-in and it can even run other manufacturer’s device models. Even if you do not normally simulate a circuit before you build it, once you get a taste of TINA-TI you will see what you’ve been missing.

TINA-TI is great as tools go. So, let’s take TINA-TI out for a spin!

I listed some important TINA-TI topics below and will pick the next topic based on your feedback. So, review the options below and let me know what looks most interesting to you! You can even suggest topics not listed here. Together we will explore TINA-TI’s every nook and cranny to give you the answers you’re looking for. 

Here is my list, in random order, for your review and comments:

  1. Differential sources and enabling AC response with them (Part 1)
  2. Importing the model of another device (non TI) into TINA-TI (Part 2)
  3. Generating a time varying / piecewise linear source (Part 4)
  4. Generating a frequency varying source (Part 4)
  5. Noise analysis (Part 3)
  6. FFT analysis
  7. Amplifier loop gain analysis – Opening the loop
  8. Analysis Tools
    • Temperature analysis capabilities and limitations
    • Laplace Arithmetic
  9. Transmission lines
  10. Test decks to uncover the behavior included in the Macromodel
  11. Difference between standalone model, TINA model, and Reference designs
  12. Where and how to use the built-in switches / relays?
  13. Implementing Noise sources
  14. Calculating power
  15. TINA-TI compatibility with Pspice
  16. Distortion or THD computation
  17. Importing a TINA-TI Macromodel into other simulators (e.g. LT Spice)
  18. Being able to “Probe” after simulation
  19. Automatic updates

While I await your responses, we’ll go ahead and cover item “1” above, “Differential sources and enabling AC response with them”.

Problem: You like to simulate a circuit which has differential input, such as this one in Figure 1 involving the high speed clamped FDA, LMH6553. When you try to AC analysis, you get the error message shown:

Figure 1: AC Analysis with more than source results in error message

Solution: In this case the solution is fairly easy as shown in Figure 2. Use controlled sources in TINA-TI to create the differential input. Done this way, you will get the proper differential input frequency sweep in AC analysis.

Figure 2: Voltage controlled voltage source (VCVS) allows a single input to allow AC analysis to run

After placing the VCVS on the schematic, double click it to assign its “Voltage Amplification”. Remember to assign the two VCVS equal and opposite amplification numbers for a differential source! You should now get…

Figure 3: VCVS opposite amplification for diff input

If you are thinking why not just use the Figure 4 implementation of a differential input, here are some reasons not to:

  1. Some simulators / simulation settings / device macromodels may baulk at the input not having a DC reference to ground
  2. There is no easy way to implement a common mode (CM) input voltage as there is in the Figure 2 method. Examples are when there is a biased center-tapped transformer driving the input, or when the input originates from a single supply differential source. To implement a CM input in Figure 2, just tie the VCVS common node to the desired CM voltage.

Figure 4: Avoid this method of implementing a differential source

If you follow the steps just outlined, you should be good to go when doing AC analysis of circuits which have a differential input.

By the way, here are some helpful sites to check out for TINA-TI:

  1. Webench Design Center: Spice models, reference designs, etc.
  2. TI E2E Simulations Forum:Find solutions, get help, share knowledge and solve problems with fellow engineers and TI experts
  3. Tina-TI An Introduction: Extensive practical guide to TINA-TI with easy to use instructions!
  4. Tina-TI An Introduction: Section 6 - Texas Instruments (an overview)
  5. Helpful Analog Wire posts related to TINA-TI:
    1. TINA-TI Free Simulator Tool Make Amplifier Sims Easy
    2. Add a little TINA to spice up your circuit

If you’d like to play around with the LMH6553 implementation I used above, click here for the TINA-TI simulation file.

Remember to send me your comments and topic requests for the next post. I look forward to hearing from you!