• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 827 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.

TLV61046A: Inductor selection and maximum current

Julien Herment11
Prodigy 40 points
Part Number: TLV61046A

Hi,

My application is really simple. The DC/DC converter is only used for less than one second to charge a 440uF capacitor @20V.  

The input is 2XAAA so minimum voltage around 2.1V. Output 20V. Charging current is limited by a P-chanel Mosfet circuit or a simple power resistor to 200mA. 

With 10uH inductor, by applying the equation in the datasheet, I have iL(DC) = 2.27A and iL(P) = 2.34A.

In the datasshet, I don't understand the following reference " Normally, it is advisable to work with an inductor peak-to-peak current of less than 40% of the average inductor current for maximum output current. "

How to choose my inductor regarding my case? Do you have any recommandation? Should I need a saturation of more than 3A? I need a small package in my case because it's for a portable device.

Thank you for your support. 

  • 0
    TI__Mastermind 46905 points
    The maximum peak current limit of the device is 1.25A, which you can find in the electrical specification table. so you can select the inductor with current rating higher than this value.
  • 0 in reply to Jasper Li
    Prodigy 40 points
    Sorry but this answer doesn't help me...
    I'm trying to understand how to choose my inductor and iSat current regarding my specific application and the value that I gave as example.
  • 0 in reply to Julien Herment11
    TI__Mastermind 46905 points
    what is your output current? you mention you are going to limit the output current?
    if not special requirement, i would suggest 10uH inductor with >1.25A saturation current device. if you require smaller solution size, you can select 4.7uH inductor. There is not strictly limitation.
  • 0 in reply to Jasper Li
    Prodigy 40 points

    The  DC current  on my resistive load will be limited to 150mA.

    If my calculation is good (assuming Vin min = 2.2V, Vout = 20V and L = 10uH), that mean iL(Peak) = 1. 86A

    In the datasheet, we have "LIM_SW Peak switch current limit = 900 to 1250mA". Is this limitation is the current flowing in the inductance ? If yes, that mean that I can use this device for my application as I have 1.86A as iL(peak).

    Thank you for your help. 

  • 0 in reply to Julien Herment11
    TI__Mastermind 46905 points
    the 900mA~1250ma is the peak current flowing in the inductor. the device will limit this peak inductor current not higher than this value.
  • 0 in reply to Jasper Li
    Prodigy 40 points
    By limiting you mean that the maximum output current will be limited to the maximum output current, not shutted down right? It's important because I'm trying to see if this part is adapted to my application. I don't want to make a wrong choice.
    furthermore in the spec, it seems that this maximum current change regarding the output voltage and input voltage but I can't see what is the maximum for my application (Vin worst case 2.2V and Vout 20V). Do you have this information?

    I can reduce my needed current to 100mA so that mean max current of 1.25A.

    However, in the TLV61046A EM (document SLVUAX3–April 2017), if we do the calculation for the spec given, the current is slightly above the limit.
  • 0 in reply to Julien Herment11
    TI__Mastermind 46905 points
    no, the device doesn't shutdown when reach current limitation.
    we can only specify this data at a special condition, but i would expect the current limit at other condition is similar.

    not sure about the third question, which current is slightly above which limit? but i think it is good idea to apply an EVM for your experiment and valuation.