• State
  • Locked Locked
  • Replies 7 replies
  • Subscribers 63 subscribers
  • Views 1436 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

3V3 output from USB 5V input (100mA) and Lithium-ion battery

Grant Downie
Prodigy 155 points
Other Parts Discussed in Thread: BQ24070, TPS62230, TPS63001

Hi,

I am wondering what solutions are available to generate 3V3 (100mA/500mA) from USB (4V75-5V25) and Lithium-ion battery(3V0-4V7). The 3V3 system is powered from USB when conected and battery when USB is not connected. When connected to USB the current consumption must be limited to 100mA until after enumeration then changed to 500mA. A MICRO controls the 100mA to 500mA change.

Regards Grant

  • 0
    TI__Guru**** 150910 points

    If you also want the USB to charge your battery, you might post in the battery charger forum and/or look at the bq24070 family of devices.

    The power interface forum might have devices that just control the current allowed to be drawn from the port.

    As to power converters, you can use the power quick search at power.ti.com to find suitable devices.  The TPS62230 family is a buck that is very small and simply to use.  If you can accept less than 3V at your load when you have a discharged battery, this would be the best solution.  If you must have 3.3V at all times, then you will need a buck boost converter, such as the TPS630x0 family.

  • 0 in reply to Chris Glaser
    Prodigy 155 points

    Hi Chris,

    Thankyou for the response.

    I need to maintain 3V3 at all times. I have looked at the buck-boost but the 400mA plus startup current is a problem from a 100mA current limited USB port. ie. does not startup properly.

    Regards Grant

  • 0 in reply to Grant Downie
    Mastermind 7395 points

    If that is a problem you could keep the PS connected to battery until the USB can deliver 500mA.

  • 0 in reply to Avi Chami1
    Prodigy 155 points

    The system is powered and battery is charged from USB when connected. The system needs to be able to start without battery or flay battery.

  • 0 in reply to Grant Downie
    TI__Guru**** 150910 points

    For that device, the current limit during start-up is 400 mA when Vout is 0V and it increases with Vout.  This energy could come from the input caps and not your input source.  The USB port will limit the current to 100 mA.  if you demand more than that, the voltage simply drops.  As long as you stay above the minimum input voltage of the given converter, this is ok and you can start-up.  You'll just need to test it out.

    The bq24070 was designed to charge a battery from a USB port.  It can greatly help your design and limit the current to 100 mA.

  • 0 in reply to Chris Glaser
    Prodigy 155 points

    I am using a device similar to the bq24070 (different manufacturer) to limit current to 100mA/500mA power path and charging. I will definately evaluate the bq24070 as it has a couple of nice features.

    I have previously tried adding a large amount of bulk capacitance to the input of the TPS63001 for the startup current and delayed enabling the TPS63001 until the capacitors were charged however I have seen the TPS63001 not start correctly on one occassion (the board sat over the weekend). I havent been able to repeat the failure by discharging board capacitors before startup.

    I will continue to investigate ...

  • 0 in reply to Grant Downie
    TI__Guru**** 150910 points

    I would need to see some waveforms of what 'not start correctly' means but this shouldn't happen.

    What is your load on power up and then afterwards?  What type of end equipment will this go into?