• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 763 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.

TPS65132 - inductor selection for boost and quasi-frequency's meaning

Given Ding
Genius 10165 points
Other Parts Discussed in Thread: TPS65132

inductor selection for boost. Since customer’s actual application do not use such high output current of POS and NEG, so they want to choose a smaller Isat inductor ( there is no need to Isat> Iswpeak), so want to check with you how to calculate the Iout-Vneg. Since it’s charge pump, Iin of charge pump should be larger than Iout of Vneg but what’s the eff of charging pump?

2. it mentioned it’s quasi-fixed frequency in datasheet, Why is it quasi-fixed?

  • 0
    TI__Guru 65470 points

    Hello Given,

    1. inductor current:

    The highest inductor current is necessary during startup, almost independent on the load current the customer is using, the inrush current during startup defines the minimum inductor current capability necessary. If you have a look on the different inrush current measurements in the datasheet you can find that a saturation current of 250mA is necessary.

    2. Charge pump output current:

    The charge pump output current is dependent of the specific TPS65132 version you are using as well as the programming of the IC. It will be either 40mA, 80mA or 150mA.

    3. Quasi-fixed frequency:

    The boost converter is not using an oscillator to set the switching frequency, so the frequency is fixed only for the given VIN, VOUT and IOUT case. It is quasi-fixed because with internal compensation, the input or output voltage changes are somewhat compensated, that the frequency does not change a lot over input voltage, output voltage and output current.

    Best regards,

    Brigitte

  • 0 in reply to Brigitte
    TI__Genius 10165 points
    Hi Brigitte,

    Thank you.
    For #1, understand that there is a low limit which is inrush current.
    For #2, sorry for make you confused. I'm asking about input current of charge pump which is the part of output current of boost. so I want to ask the eff of charge pump.
    Thank you.

    BRs
    Given
  • 0 in reply to Given Ding
    TI__Guru 65470 points

    Hello Given,

    #1: correct, the inrush current limits the low value of the inductor current

    #2: Due to the fact that this is an inverter charge pump, the input current is in theory the same as the output current. But due to some losses inside the charge pump, the input current will be somewhat higher. So I would estimate an increase of 20% to be on the save side.

    Why do you want to know this?

    Best regards,
    Brigitte