TNY264 Changed, Obsolete, What? Help!
Please help me out with this part as many things appear to have changed. I designed a supply around this part back in 2003 with an EE13 transformer. However,
1. PIExpert now shows the switching frequency as 120KHz rather than the datasheet and previously designed value of 132KHz. Which is correct? It really was 132KHz at some point in the past. If it changed, when did it change?
2. TNYII are now archived. Are these intended as "not for new design?" If so, why do you have only a 4 year product life?
3. Can TNYIII "drop in" to the previous TNYII design? What are the design differences between TNYII and TNYIII?
4. My desire was to keep the previous power supply design intact and just build a related product around it. Will the design be "doomed" to premature obsolescence if I do this? I wish to have a seven to ten year product life for a launch in third quarter 2009.
Thanks,
Mike Magargee
Comments
I've just spoken with our customer service department and they assure me that TNY-II products are not obsolete and are still available for purchasing and use in designs. The confusion probably arose because we move old products into our product archive when we launch a newer version of the family. You are more than welcome to continue designing with TNY-II parts, however we recommend considering the new TinySwitch-III family devices for any new designs. TinySwitch-III implements a number of new protection and performance features which will improve the field reliability of your designs and provide more flexibility in adapting your designs to multiple applications.
Unfortunately, TNY-III devices are not drop-in replaceable in older TNY-II designs. The functionality changes are different and will require different component values in your circuit for correct programming. If you iterate your design using PI Expert, it will greatly assist you in re-designing your supply for a TinySwitch-III part and will suggest component values for your design. Again, this redesign is optional as TNY-II parts are still available.
Thank you for the feedback. I can understand the website strategy of positioning II and III. My dilemma regarding III versus II is that I had a transformer wound for the previous II design and don't want to go through UL again--I would rather have a root canal. So I have been tweaking optimization parameters based on the old transformer core until the magnetics from PIExpert 7 match the values from version 6 (to compare performance of the tool). Then I thought I would try a new design with TNY III and again try to match the previous parameters.
Have PIExpert's calculations changed between versions 6 and 7? I'm finding differences in the primary inductance and gapped core effective inductance.
Mike
Hi Mike -
Short answer
Yes, you can use the same transformer while designing with TinySwitch-III. The tolerances on the TinySwitch-III family are much tighter as compared to the Tinyswitch-II family and so there should be no problem with the higher inductance transformer.
Long Answer
The reason the inductances are different when desiging with TinySwitch-II and TinySwitch-III is because TinySwitch-III has a control parameter called "I^2F" which makes it impossible for any given part to simultaneously have the lowest current limit AND the lowest switching frequency. The result is that you can now specify a lower inductance transformer as compared to a TinySwitch-II design (where to design for worst case the software does design the inducatnce based on lowest frequency AND lowest current limit)
Another reason for the slight discrepency is that it appears that this design was done using version 4 of the software (which has the extension .udx). This is a much older software revision and we continuously make slight adjustments and improvements to the software (like updating efficiency numbers and adding support to newer devices like TNY263 and TNY265)
If you'd like I can further investigate the slight difference you are seeing in the inductance by taking a look at your original design file (.udx file). However as I have indicated above, the higher inductance transformer that you have will still work perfectly well with the TinySwitch-III family also.
The nominal switching frequency of TNY264 regarding your question is 132kHz. We've designed TNY264 with frequency jittering for dramatically reducing EMI. So, you will see a switching frequency range from 120kHz to 144kHz. Please make sure you are using the latest version of PIExpert. In my PIExpert, I saw the following frequencies:
fS 132000 Hertz TinySwitch-II Switching Frequency
fSmin 120000 Hertz TinySwitch-II Minimum Switching Frequency (inc. jitter)
fSmax 144000 Hertz TinySwitch-II Maximum Switching Frequency (inc. jitter).
TinySwitch II are now archived and if you are going to have a new design we suggest that TNYII is "not for new design" because we have newer TinySwitch III. It has nothing to do with product life and you can still keep using your old design.