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TLV61046AEVM-833: cannot get EVM to support 3.0 - 4.2V Input, 5V Output, 100mA Out

David McRell
Intellectual 445 points
Part Number: TLV61046AEVM-833
Other Parts Discussed in Thread: TLV61046A, TPS61240

Hello!

We have TLV61046A EVM.  I need help with the following: EVM does not make 5V output with the parameters mentioned in the subject and below.

Our circuit goal is the following:

Input: 3.0 - 4.2V
Output: 5.0V, 100mA (75mA nominal)

The EVM has the following changes:
R1 = 374k
L1 = VLCF4020T-100MR85
C2 = 10uF/10V + 22uF/25V, or only 10uF/10V

Input supply = workbench power supply
Load = resistors

Observations:
1) With 100mA load, EVM output is ~2.5V if TLV61046A is enabled while input voltage is < 3.9V*; switching period becomes 2.4us with 15% duty cycle (switch on)
1a) if the input voltage is lowered in 0.1V steps, the output remains 5V until input is < 2.1V

2) With 50mA load, output is ~2.5V if TLV61046A is enabled while input voltage is < 3.1V; switching period and duty cycle are similar to item 1 above.
2a) if the input voltage is lowered in 0.1V steps, the output remains 5V until input is < 1.6V

3) For the parameters stated in the above "circuit goal", WebBench reports "Duty Cycle is lower than the minimum for this device".  If I lower input voltage to 3.8V, WebBench has no error.

* 3.9V becomes 3.7V if 10uF/10V cap is used without 22uF/25V present.

Any recommendations?  larger inductor?

Side note: we like the output disconnect feature.

Many Thanks!

David McRell

  • 0
    Intellectual 445 points
    Hello,

    I have an update. I found a 22uH in my available parts.

    L1 = NR10050T220M (overkill, but it is what I have available quickly)

    Observations:
    1) With 100mA load, EVM output is ~2.5V if TLV61046A is enabled while input voltage is < 3.7V*; switching period becomes 2.4us with ~15% duty cycle (switch on)
    1a) if the input voltage is lowered in 0.1V steps, the output remains 5V until input is < 2.0V

    2) With 50mA load, output is ~2.5V if TLV61046A is enabled while input voltage is < 2.6V; switching period and duty cycle are similar to item 1 above.
    2a) if the input voltage is lowered in 0.1V steps, the output remains 5V until input is < 1.6V

    I forgot to mention that when 5V is on the output, switching period is ~890ns with ~50% duty cycle.

    Thanks!
    David McRell
  • 0 in reply to David McRell
    TI__Guru* 78070 points
    Hi David,

    Our expert of this part is currently on weekend. Your question will be answered soon.

    Thanks,
    Youhao Xi, Applications Engineering
  • 0 in reply to David McRell
    TI__Mastermind 46905 points
    Hi David,

    The device should work in the condition you mention. what happen if there is no loading in the output? Could you try to startup the device firstly, then apply the loading? the device has short circuit protection which will limits the loading during startup.

    for only 5V output, you can use TPS61240,which is higher efficiency and smaller solution size.
  • 0 in reply to Jasper Li
    Intellectual 445 points

    Hello Jasper,

    Thank you very much for your helpful reply.

    While I had to find a different solution due to deadline, I still need to return to this later and learn more about the 61046A.  When I have time I will likely report more results to you and ask more questions.

    The TPS61240 is very intriguing.  I will add this to our consideration.

    Thank you again!

    David McRell

  • 0 in reply to David McRell
    TI__Mastermind 46905 points
    Hi David,

    OK. I closed the post. but you can just reply the post if you want to ask further question.