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TPS61230: Vout level is incorrect unless Rload is disconnected and then reconnected during EN state

Lonnie Adams
Prodigy 175 points
Part Number: TPS61230
Other Parts Discussed in Thread: TPS61023, , , TPS61022

Vout is not regulating to design parameters unless the Rload is removed and reattached or wiggled.

Rload varies from 1.6Ohms to  2.6Ohms depending on make and model of the external Vape Cartridge Atomizer

Vout is set to 4.2V

My schematic and physical board design followed the datasheet and Webench constraints.

The design includes a microcontroller to control the EN pin of the TPS61230 device when a user asserts an external button/switch.  When the but/swtch is pressed the microcontroller asserts the EN pin and the TPS61230 powers the Atomizer.  At  the initial power on state (EN Asserted) the Vout never exceeds 1.28Volts  and remains at this level as long as the button is asserted.  Once the  button is no longer pressed the EN pin is taken to a low level and Vout goes to 0.0V, TPS61230 disabled.

During the initial power on state and while Vout is at 1.28V; if Rload is disconnected and then reconnected Vout will rise to the design Vout of 4.2V.  Wiggling Rload will accomplish the same results.  

  • 0
    TI__Intellectual 2645 points

    Hi Lonnie,
      TPS61230 has about 2.5ohm load capacity at start up. If your load is 1.6ohm, TPS61023 can't start up. 
      You could make the load is 3ohm and then start up.
      You could find the start up capacity by EC table.

  • 0 in reply to Jing Ji
    Prodigy 175 points

    Jing;

    Can you be more specific and explain the Precharge Current Limit table.  The only 2.5ohm value is Vout=5/2.0A

    Thanks

  • 0 in reply to Lonnie Adams
    TI__Intellectual 2645 points
    Hi Lonnie,
    At start up, the rectifying switch turns on with a current limit (Precharge current). This current limit is related to Vout.
    If you set Vout=4.2V, at the start up, Vout rises from 0V to 4.2V.
    From EC table,
    Vout=0V Ioutmin=0.4A, it could start up with very heavy load. and then Vout inceases to 3.5V.
    Vout=3.5V Ioutmin=1.8A, it could start up with 1.9ohm. and then Vout inceases to 4.2V.
    Because we don’t have the data at Vout=4.2V.
    We use Vout=5V to estimate it.
    Vout=5V Ioutmin=2A, it could start up with 2.5ohm.
    We need to guarantee Vout from 0V to4.2V, boost could start up. So we need Rload is bigger than 2.5ohm.
  • 0 in reply to Jing Ji
    Prodigy 175 points

    Jing;

    I  confirmed your output resistance values with my TPS61230DRC circuit by removing my load and replacing it with a range of resistors.

    I also have a TPS61230AEVM-767 development board and have  been working with it using both resistor  values and vape atomizers.  the development board works for all atomizers and low resistors, but if you look at the Ilim from the EC table it would appear to be similar.  Please  comment.  thanks

  • 0 in reply to Lonnie Adams
    TI__Intellectual 2645 points
    Hi Lonnie,
    Could you share you SCH and layout with me? I will review it, firstly.
  • 0 in reply to Jing Ji
    Prodigy 175 points

    Jing;

    send   me your personal email as  this project is for an outside client and I'm not at liberty to share.

    My main question at this time is why the TPS61230A Evaluation board works with all the atomizers and low resistance.  Isn't the Ilim_pre near the same as the TPS61230DRC device?

    from the TPS61230A data sheet:

    ILIM_PRE Pre-charge mode and short circuit current limit (DC charge mode) Linear mode, VOUT = 2.5 V 1.02 A Linear mode, VOUT = 0 V 0.06 0.6 A

    thanks

  • 0 in reply to Lonnie Adams
    Prodigy 175 points

    Jing;

    Here's what I  just discovered this morning with the TPS61230A Evaluation Board.  I'm  using a single Li-Ion battery (4.2V) as the power source.  As long as the battery voltage is between 4.0 - 4.2V the circuit will drive the Atomizers,  but once the voltage drops below 4.0V it will no longer drive the output.  If I substitute a 4.0-Ohm resistor for the Atomizer it works.  

    Questions; can you suggest a TI component for my application of driving low resistant Atomizers (1.5 - 2.2  Ohms)?

    Comments?

    Thanks

    Lon

  • 0 in reply to Lonnie Adams
    Prodigy 175 points
    Jing;
    Working with the development board again I just discovered that by attaching an additional gnd connection to the housing holding the Atomizer that all three Atomizers work. I'm going to continue testing tomorrow and monitor the results. Lon
  • 0 in reply to Lonnie Adams
    Prodigy 175 points

    Jing;

    To give you more data..

    I  have three Atomizers with the resistance values of 1.8Ohm, 1.4Ohm and 1.4Ohm  after  taking into account the internal resistance  0.2Ohm of the meter.

    I'm still using the TPS61230ARNS development board  SLVUAS8A

    with a battery voltage of 3.5 - 4.2 the circuit works and energizes either of the three Atomizers, but after the battery drops below +3.5V I  no longer get a solid output voltage, but rather an oscillating signal.

    Thoughts?

  • 0 in reply to Lonnie Adams
    TI__Intellectual 2645 points
    Hi Lonnie,
    Sorry for the delay because I am busy these days. I thinks this problem is because load capacity at start up. and normally it is related to Vin and Vout. We have a new device tps61022 , which could support this start up current. we can talk about it by Email