• State TI Thinks Resolved
  • Replies 8 replies
  • Answers 5 answers
  • Subscribers 63 subscribers
  • Views 136 views
  • Users 0 members are here
Support feedback
Options
Options
Related

Original question:

UCC25660: TSET datasheet values vs design calculator

UCC25660: UCC25660/UCC25661 TSET pin timer gain calculation.

Carlo Sun
Prodigy 20 points
Part Number: UCC25660

Tool/software:

The IPCC parameters calculation need to know kt.

From datasheet and calculator, we can know that kt is timer gain and influenced by TSET pin resistors. But how should we calculate it?

  • 0
    TI__Guru 50090 points

    Hi Carlo,

    Option 1 only applies to the UCC256616, for all other variants, use option 2. 

    Based on you selection for the integrator time constant, the excel calculator will recommend the correct resistor values. 

    I hope this answers your question. 

  • 0 in reply to JCHK
    TI__Prodigy 20 points

    Hi Jchk

    Thanks for replying. I really want to know how the timer gain kt is calculated, because the calculator only provides calculated values. Does it have a clear calculation formula?

  • 0 in reply to Carlo Sun
    TI__Guru 50090 points

    HI Carlo,

    Unfortunately no. I checked and the excel calculator is using a lookup table to select the kt value. 

    I would have to check to see if we can share how this is calculated.

  • 0 in reply to JCHK
    TI__Prodigy 20 points

    I appreciate that. Cause we want to provide customers with a detailed calculation plan.

  • 0 in reply to Carlo Sun
    TI__Guru 50090 points

    Hi Carlo,

    I will see what I can find. 

    Regards,

    John

  • 0 in reply to JCHK
    TI__Prodigy 20 points

    Hi JCHK,

    One more thing, is the Vcm's value mentioned in the data sheet? I can't find it.

  • 0 in reply to Carlo Sun
    TI__Guru 50090 points

    Hi Carlo,

    VCM is the internal common mode reference for the device here you can see it used for ISNS and how it does the IPOLARITY detection.:

    I am still checking on how kt is calculated, but suspect we will not be able to share this. 

  • 0 in reply to JCHK
    TI__Guru 50090 points

    Hi Carlo,

    Sorry for the delay. I don't have the detailed derivation, but here are the kt values as a function of the TSET option chosen:

    TSET Option No.  TSET Voltage (V) Minimum Frequency for IPPC operation (kHz) Integrator Time Constant (ns) Maximum Dead-Time (µs) kt
    17 2.295 698.6 68 0.5 14.293
    16 2.168 591.6 80 0.5 12.104
    15 2.041 501 93 0.5 10.25
    14 1.914 424.3 112 0.5 8.68
    13 1.787 359.3 132 1 7.351
    12 1.66 304.3 156 1 6.225
    11 1.533 256.7 184 1 5.272
    10 1.416 218.2 214 1 4.484
    9 1.299 184.8 257 1 3.781
    8 1.182 156.5 304 1 3.202
    7 1.074 132.5 359 1 2.711
    6 0.967 112.2 424 1 2.296
    5 0.85 95 490 1 1.9445
    4 0.742 80.5 588 1 1.6465
    3 0.644 68.1 694 1 1.3945
    2 0.547 57.7 820 1 1.181
    1 0.45 48.9 968 1 1

    I hope this answers your question.