TPS5430: Inductance selection

xingwitt

Part Number: TPS5430
Other Parts Discussed in Thread: TPS5450

Hi team,

I have a question here, if I give 30V input and the output is 15V, but the current of the rear end load is only 0.01A

According to the formula for calculating the inductance，Lmin=Vout*(Vin-Vout)/(Vin*Kind*Iout*Fsw),=15*15/(30*0.3*0.01*500000)=0.005

then Lmin=5000uH.

Would this be a problem if I had selected a 22uH inductance following a typical circuit on the data sheet?

Also, If I swap the connection between the output and the ground, will the output become -15V?In this situation, Vout*(Vin-Vout) will stay 30*(15-15) or be (-15)*(30+15)?

8 months ago

0 Colin Chen 8 months ago

TI__Genius 12901 points

Hello Sir,

The inductance calculation based on Iout_max not the load current.

If you swap the connection between the output and the ground. it will be a inverting buck boost topology.

You can refer to below app note for further design:

https://www.ti.com/lit/an/snva856b/snva856b.pdf?ts=1706776466459&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fen-us%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526searchTerm%253DSNVA856A%2526nr%253D1

Thanks

Colin

0 xingwitt 8 months ago in reply to Colin Chen

Prodigy 130 points

Hi，

I don't understand,what does Iout_max mean? If the maximum current I need is 0.01A(and if it is 0.01A while I use)，then is the value of Iout_max 0.01 in that formula? In this case, I cannot find a proper inductance.

0 Colin Chen 8 months ago in reply to xingwitt

TI__Genius 12901 points

Hello,

The Iout_max means the maximum current that device can output, not the maximum current you need.

Taking the TPS5450 for instance, you should take IOUT=3A into your calculation.

Thanks

Colin

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TPS5430: Inductance selection