• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 63 subscribers
  • Views 288 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.

LMR62421: package when using it as a sepic converter

Ainara Calvo
Prodigy 140 points
Part Number: LMR62421
Other Parts Discussed in Thread: TLV61048

Hi there,

I have a system supplied by a litium battery and I need to generate 12V and 3,8V. For the 12V generation I've choosen the LMR62421.

To minimize the number of different references I'm thinking of using the same ic to generate 3,8V, but the battery goes from 2.7V to 4.2V. I've seen in the datasheet that the LMR62421 can be used as SEPIC converter, but the example uses the WSON package, Can I use the SOT-23 package as SEPIC converter too? I wpuld like to confirm that because we are soldering ir ourselfs and the SOT-23 is easier to solder.

it would be a problem if I design the generation of 3.8V with the LMR62421 as boost controller? I mean, is there a problem if I have a 2,7 to 4,2V input and I use the LMR62421 as boost controller to generate 3,8V output? How would it work with a Vin > Vout?

Thanks in advance,

Regards,

Ainara

  • 0
    TI__Mastermind 34231 points

    Hi Ainara,

    Could you let me know the output current of 12V and 3.8V?

    There is no difference to use SOT-23 package and WSON package. 

    If you configure it as a boost controller , when Vin > Vout, Vout will follow Vin so it means vout could be stable at 3.8V. 

  • 0 in reply to Zack Liu
    Prodigy 140 points

    Hi Zack,

    thanks for your answer!

    The output current would be no more than 200mA for each of them, I believe the LMR62421 is able to give up to 0.5A, right?

    I thought that there was no difference, but I just wanted to make sure, beacuse, even though it does not say anything about having different funcionalities for different packages, the only example for the SEPIC converter functionality was with the WSON package.

    So can I just configure it as boost controller even when Vin>Vout? the thing is that, because we are using a battery as our power source, it will start as Vin>Vout but it won't be long until Vin decreases to Vin<Vout in which case the boost controller configuration will suit perfectly. which configuration do you think is better for this scenario?

    Regards,

    Ainara

  • 0 in reply to Ainara Calvo
    Prodigy 140 points

    Hi Zack,

    Another question, I've read in the datasheet that the Quiescent Current(switching) is typicaly 7mA, but, what does this mean?is it the case where when there is no load?or all the time it is enabled? It is really important for us because most of the time the system will be on hold, consuming about 5uA from the 3,8V. that 7mA is too much current compare to that.

    Thanks,

    regards,

    Ainara

  • 0 in reply to Ainara Calvo
    TI__Mastermind 34231 points

    Hi Ainara,

    The 7mA of quiescent current (switching) means the input current from battery at no load condition. Do you have a MCU to control EN pin? When the system is being on hold, disable the IC and the IC will draw only 80nA only. 

  • 0 in reply to Zack Liu
    Prodigy 140 points

    Hi Zack,

    We have a MCU but it is going to be supplied from that 3,8V, so the IC will have to be enabled all the time. the only thing that is going to be connected to the 3.8V IC is the MCU so it will have a load, but a very low one. In this case, with a load of 5uA, what would be the Iq? The 12V IC will be disabled and that 80nA are great.

    Regards

    Ainara

  • 0 in reply to Ainara Calvo
    TI__Mastermind 34231 points

    Hi Ainara,

    I suggest you use TLV61048, which is has power save mode at low load current, drawing lower current from battery.

    So using one TLV61048 to generate a 3.8V as MCU power supply and another one to generate a 12V Vout. Using MCU to control 12V boost converter.

  • 0 in reply to Zack Liu
    Prodigy 140 points

    Thank you so much Zack for your atention.

    Kind regards!

    Ainara