• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 62 subscribers
  • Views 1266 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

Limiting inrush current in TPS61220 family

Ryan Aylward
Prodigy 40 points
Other Parts Discussed in Thread: TPS61222, TPS61220, TPS61070

I am testing a new design using the TPS61222 to generate 5V from a 2AA battery pack. The 5V rail is only required for a subsystem containing LEDs - the MCU runs directly off the battery. When the regulator is enabled in order to supply power to the 5V subsystem, an inrush current of up to 200mA is possible as the output cap charges. This causes the battery voltage to drop to the point where the MCU could be reset, even from a moderately low battery.

I noticed that the TPS61222 info page (http://www.ti.com/product/tps61222) links to an application note about addressing this exact problem with the TPS6107x family of converters (http://www.ti.com/lit/an/slva307/slva307.pdf). The soft start circuit described in this application note seems like it could be used on the TPS6122x family as well, especially if I switch to the adjustable voltage version TPS61220, which gives access to the feedback network. However, the internals of the two converter families are a bit different.

Can I apply the soft start technique for the TPS6107x to the TPS61220? What about techniques to limit the inrush current in the fixed-output TPS61222?

 

Thanks,

Ryan

  • 0
    TI__Guru*** 142750 points

    The TPS61220 has a key feature that greatly affects the inrush current--it has a diode connecting L to Vout even when it is off.  So, you cannot stop the inrush occurringthrough this diode.  Is this desired for your system?  Since you are simply driving LEDs, I would expect this to be undesirable since the LEDs could never be fully turned off00the IC always applies a voltage on them.  My app note cannot affect this inrush current from the diode.

    I recommend using the TPS61070 which has a battery disconnect built in.  Its inrush can be controlled by my app note. 

    Other options are adding an RC filter to your MCU to hold up its voltage to ride through the dip in Vin.  Or you could reduce the Cout, which does not need to be very high for an LED driver.