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TIDM-DC-DC-BUCK: TIDM-DC-DC-BUCK with LAUNCHXL-F28069M is not working.

Saunak Bhalsod
Prodigy 160 points
Part Number: TIDM-DC-DC-BUCK
Other Parts Discussed in Thread: LAUNCHXL-F28069M, BOOSTXL-BUCKCONV

Dear TI Experts,

I am using TIDM-DC-DC-BUCK(http://www.ti.com/tool/TIDM-DC-DC-BUCK) Converter with LAUNCHXL-F28069M. 

I have taken reference from the document http://www.ti.com/lit/ug/tidu986/tidu986.pdf

I have done exactly the same as it is explained in the reference document. 

1.3.6 Run the Code

1. Press F8 to run the code.

2. Turn on the 9-V supply.

3. Observe Gui_Vin in the watch window (it should now be 9 V).

4. Turn on switch SW1 on the BoosterPack.

5. Increase Duty1A_Set to 0.3 in Q24.

6. Observe the output voltage Gui_Vout1.

When I am at Step 2 turn on the 9V supply, I am getting 9V at expression window. before turning on the switch SW1.

But, when I am turning on the Switch SW1, I should get almost 0V because my duty is 0 but I am getting some 6V at output.

 

Input voltage is also dipped to 8.7V and load resistance (PR1) getting heated. FaultFlag has been set to 1.

it looks like something is shorting. But this is the first time I am using the board. How that is possible?

I have checked the PWM pulses at PWM4A and PWM4B. Both are zero. but still output is comming 6V.

Kindly, help regarding this. 

  • 0
    TI__Guru 62975 points
    Saunak,

    It does sound like something might be wrong with the BOOSTXL-BUCKCONV. I recommend requesting an exchange from your place of sale.

    -Tommy
  • 0 in reply to tlee
    Prodigy 160 points

    Dear Tommy,

    Thanks for the answer,

    After analyzing the waveform, I came to know that even though I am not connecting Launchpad (No PWM Control pulses) some DC voltage is coming.

    Then I have observed the SW node voltage. It is also same as output voltage. From this we can conclude that the upper switch is continuously turned on. 

    And Output of driver also high. So it could be Driver or MOSFET problem. One more thing I would like to suggest that in the schematic the Vdd supply of the Driver IC is mentioned as before Switch SW1 but actually it is after SW1. You can correct it.

    Thanks and Regards

    Saunak Bhalsod

  • 0 in reply to Saunak Bhalsod
    TI__Guru 62975 points

    Saunak,

    That is a good job of debug. I will see about updating the schematic.

    -Tommy