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TPS63031: Inductor selection / VINA and VIN issue

FAB63476
Intellectual 530 points
Other Parts Discussed in Thread: TPS63031

Hi!

I am designing  a dc dc converter with TPS63031 and I have many questions regarding the datasheet.

1- 

I wonder if I could use as an inductor a Multi Layer Chip Inductor as CBC2012T2R2M since all the options provided within the datasheet are huge inductors.

I have reduced the inductor size because I need only  200 mA of current output.

2- 

Page 16 of the datasheet says that bypass capacitor shouldn't be higher that 0.22uF (connected to VINA). Then Input capacitor is 4.7uF. So the VIN and VINA pins shouldn't be tied up to the same potencial.

However, I have seen in Switcher pro design software that suggest VIN and VINA tided up. Also the same datasheet  shows in the 1rst schematic at page 1 VINA and VIN tied up. Looking at the internal layout, there is a resistor between both terminals.

Is a little confusing. I think I will separate thoe ports, but I would like to understand the dicrepancies.

thanks!

  • 0
    TI__Guru**** 150610 points

    I would caution against using an inductor with such a small saturation current rating.  Though you may only have 200 mA of output current, when you are in boost mode, the inductor will see currents much higher than this.  It should not saturate under these conditions.  Furthermore, during start-up or load transients, the inductor current may go higher than what it is as steady state.  For these reasons, we recommend using an inductor with a saturation current rating greater than the IC's current limit.

    Would Coilcraft's XPL2010 be small enough for you?

    There are several design notes in the forums about other TPS630xx ICs that discuss the VIN to VINA connection and internal resistor.  These design notes also apply to the TPS63031.  If you still have questions after reading those, just post back here.